Mc_Reatta's cooling fan modification

[drtidmore]

Does anyone have the wiring diagram of Mc_Reatta's plug and play modification that forced BOTH engine cooling fans to run at HIGH speed whenever the ECM called for either low or high operation?  As Mc_Reatta is no longer on the forum and no one seems to have been able to reach him in some time (an unfortunate loss to the forum), I am hoping that someone has the details or one of the pigtails that could be reverse engineered.

[DAVES89]

I have one of the pigtails [I think it is laying around somewhere]. He gave me one for each one of my Reattas in payment for parts sold to him. I removed it from the Black as I only drive the car in cool months.

 I can make it available for reverse engineering if you want and I can find it. 

[DAVES89]

I did find it. It is what I suspected. He built a lead that plugs in the harness at the connection below the fuse box.

 At that point there is a male/female connection just for the fans. He unplugged the pigtails at that point and made an 8"  lead. On the male end of his pigtail he jumpered the yellow and green leads on the male together. [It would be the two leads closest to the snap lock]. He did nothing to the female end.

 This allows both fans to run on high. 

 He never told me what he did he just built them and sent them to me. I have had them in my Red for 6 years and never a problem.

 All I did was peel the hink shrink back on both the female and male ends [the heat shrink was never shrunk down] and looked at it. I didn't see [or feel] any resistors or anything else under the heat shrink.

[drtidmore]

Dave,

Thanks for the reply.  Let me see if I can take what you found and relate it back to the schematic for the fans.  Sounds like he made the mod after the relays based on what you stated which would mean that the ECM quad driver module would think everything was fine as it ONLY monitors the coil side of the relays. I will get back with you.  Thanks again!

[DAVES89]

David, sorry but I omitted one thing. The four wires are still intact to each plug,but what Mc_Reatta did was ADD one wire to each of the two pins on the male plug end closest to the snap lock and joined these two added leads together.

 Soory for the incomplete answer.

Edited April 13, 2017 by DAVES89 (see edit history)

[Ronnie]

2 hours ago, DAVES89 said:

David, sorry but I omitted one thing. The four wires are still intact to each plug,but what Mc_Reatta did was ADD one wire to each of the two pins on the male plug end closest to the snap lock and joined these two added leads together.

 Soory for the incomplete answer.

 

Below are photos of the fan modification lead that Mc_Reatta made for Dave.

 

 

[DAVES89]

Thanks Ronnie!

 Ronnie being more knowledgeable then me says it looks like there may be a diode or something in the red lead. If so what do we do? Is this something I can measure?

[drtidmore]

If it is a diode it will only conduct in one direction.  Take your digital volt ohm meter and measure the ohms across those red leads, then reverse the test leads and measure again.  If it is diode there will be huge difference in the resistance between the two readings.  One will likely be in the low 1000s or lower and the other well into megohm range, so watch the scaling on the meter as most autorange and so you need to verify the range it chose in order to make sense of the numeric reading.  

 

Ronnie, thanks for jumping in and helping on this.

Edited April 13, 2017 by drtidmore (see edit history)

[drtidmore]

I suspect a diode as in reading Mc_Reatta's posts for the day, he mentioned that he had to trick the ECM into believing all was well.  I have come up with a design that involves adding in an additional relay in one of the blank sockets in the engine compartment relay center but it is more involved and certainly not as easy an install as what Mc_Reatta created, but still not rocket science either.  I have yet to implement it as I wanted to understand what Mc_Reatta did previously in comparison.  

[DAVES89]

I will measure it as you ask.

 I will say that when Mc_Reatta and I discussed this [6 years ago, I still have the PM's] he said he could make and sell them for a reasonable price [$40.00 or less]. He also wanted them to be "Plug and Play" and easily reversed without doing any changes to any harness. 

 I have three, two of which are installed. I will say that it works great as I run 195 degree thermostat and never have I gone above 209. And I have driven both the Red and the 'vert in all temperature ranges in many parts of the country.

 His idea is really simple; Get two plugs, run wires from plug to plug and jumper the two outside wires with a diode. Everything cheap and easily reversed. It's an easy install. The connection you tap this jumper into is located right under the relay box under the hood.

 Maybe I should look into having them made up.

 Any interest? 

[Ronnie]

When you enlarge the photo there appears to be two components connected in parallel under the shrink wrap. One appears to be the shape of a small resistor. The other one could be another resistor, a diode, or a reed switch. It's hard to tell without actually seeing the components. If there are two components, just testing with a meter may not tell you want you need to know to make another pigtail.

 

This is just speculation but I think what he did was use the ECM ground signal (connector pin A ) for the low speed fan relay to pickup both the low fan relay and the high fan relays at the same time via the red jumper wire in the pigtail. When the engine temp reaches a certain point the ECM provides another ground signal (connector pin B ) to run the fans on high speed.. Simply connecting pin A and pin B together would probably cause a problem of either the ECM throwing a code E026 or interfere with the cooling fan relays working as intended when the pigtail is installed. Therefore there needed to be some minor electrical modification made to the red jumper. I think we really need to know what is under the shrink tubing to get to the bottom of this.

 

My hat is off to Mc_Reatta for figuring all this out and taking the time to make the pigtails.

 

 

 

 

 

 

Edited April 13, 2017 by Ronnie (see edit history)

[drtidmore]

Dave,

I really don't know how many out there are interested in the low speed bypass option.  I suspect it is a small group, but given the ease of construction, low cost and ease of installation of Mc_Reatta's design, there would not be a lot to loose in making up some and seeing how well they sell.  Finding the proper connectors would be the biggest effort if going into production.  I know that many of the OEM connectors can be purchased still so it is a matter of researching and finding a source.  

 

 

[drtidmore]

48 minutes ago, Ronnie said:

I think what he did was use the ECM ground signal (connector pin A ) for the low speed fan relay to pickup both the low fan relay and the high fan relays at the same time via the red jumper wire in the pigtail. When the engine temp reaches a certain point the ECM provides another ground signal (connector pin B ) to run the fans on high speed.. Simply connecting pin A and pin B together would probably cause a problem of either the ECM throwing a code E026 or interfere with the cooling fan relays not working as intended when the pigtail is installed. Therefore there needed to be some minor electrical modification made to the red jumper. I think we really need to know what is under the shrink tubing to get to the bottom of this.

 

My hat is off to Mc_Reatta for figuring all this out and taking the time to make the pigtails.

 

Ronnie, I have played with this on and off for a couple of years.  Yes, the "A" signal from the ECM CAN be jumped to "B" and used to fire up the high speed relays, but as you suspected it throws an E026, but oddly enough ONLY after the car gets up to about 20 MPH or so.  You can operate it with "A" and "B" jumpered with the car stationary and it will NEVER throw the E026.  My initial thoughts were that QDM1 (controls "A") was detecting the added current draw of the 2 high speed relay coils when I jumpered "A" to "B" but then I decided to just ground "B" as a way to isolate QDM1 from the equation and I got the exact same results.  I found this puzzling as the FSM states the QDM2, which grounds the 2 high speed relays, will NOT throw a E026 as there are several conditions that can present a mismatch to QDM2 (remember each QDM controls upto 4 grounding circuits).  As the ECM ONLY monitors the relay coils, not the actual contacts or the fans, it is a bit of a mystery as to how the E026 is being tripped (wish GM had provided more than a single fault code on the QDMs). 

 

But if I understood Dave, the pigtail plugs into the harness going to the fans which would be AFTER the relays, so I had thought that Mc_Reatta might be driving both fans using JUST the low speed relay but not so sure of that after seeing the pics.  I need to dig into the wiring and get a handle on the Mc_Reatta mod.

 

Now that I see the closeup of Mc_Reatta's pigtail, I agree that there are TWO things under that heatshrink.  Looking at the pic, it appears that there are bulges at the ends of both whatevers are under the heatshrink and many resistors have those bulges, but I have never seen diodes have them.  

 

I have a paper design that I know will work and it has the added benefit of allowing the fans to run in low speed mode as long as the engine stays below a user set threshold (i.e. like the OEM design, tripping them at more like 180-185 rather than 225.  It involves swapping a few connections in the engine compartment relay center and adding in an additional relay in one of the blank sockets.  The design retains the use of the OEM relays for the actual fan control.  It also does NOT confuse the QDM in the ECM.  With the addition of a SPST switch, I can add an OEM only functional option.  I likely will implement the design, but I wanted to understand Mc_Reatta's design.  

 

I know that my design would likely not be one that would find widespread use due to need to deal with the mods to the relay center, so figuring out Mc_Reatta's design should be undertaken so as to offer a simple, inexpensive, plug and play option to the community.

Edited April 13, 2017 by drtidmore (see edit history)

[DAVES89]

3 hours ago, drtidmore said:

Dave,

I really don't know how many out there are interested in the low speed bypass option.  I suspect it is a small group, but given the ease of construction, low cost and ease of installation of Mc_Reatta's design, there would not be a lot to loose in making up some and seeing how well they sell.  Finding the proper connectors would be the biggest effort if going into production.  I know that many of the OEM connectors can be purchased still so it is a matter of researching and finding a source.  

 

 

 I go to Gibson's all the time and there are 3 Reattas and about 7-10 Rivs, and Trofeos out there. I just cut the harness conections with about 4-6" of lead on each plug and I am pretty much in business.

[DAVES89]

There are two resistors inside the heat shrink. Each one measures 34 ohms. Ronnie has the pictures...

[Ronnie]

Below are Dave's photos. I've cropped them to get a closeup view.

 

I'm surprised just to see two resistors in parallel. I was really expecting to see a diode in there too. Dave, in the first photo, the shrink tubing that you haven't removed seems to be a little thicker under your fingertip than what is around the wire. Could there be something else in that thicker area?

 

 

 

[DAVES89]

I just went and stripped the heat shrink the rest of the way. It was a bare wire wrapped around the lead wire and "extra" solder as he wanted to be sure it was a good connection. Nothing else there but those two 34ohm resistors...

[drtidmore]

So Mc_Reatta was just doubling up the wattage rating to 1/2watt with the two 1/4watt, 69ohm resistors in parallel for an effective resistance of 34 ohms (note the color code on each resistor is for a 69ohm resistor which in parallel results in a nominal 34.5ohms.  I need to verify where that connector that Mc_Reatta's pigtail mod inserts to better understand what he did and how it precludes E026 errors. 

[Ronnie]

Hum. I'll have to look at the schematic again to see if I can figure out why the resistance was needed. According to the color code on the resistors each one is a 68 ohms. When you tie them in parallel like that the meter will read 34 ohms total resistance.

 

BTW, The shape of the connectors he used, and the location where you installed the pigtail, tells me the pigtail connects to the control circuit of the relays. In other words it connects between the ECM and the fan relay coils and not on the power side (contacts) of the relays. The resistors are used to fool the ECM to keep it from throwing a code 26 and David mentioned earlier.

[Ronnie]

1 minute ago, drtidmore said:

So Mc_Reatta was just doubling up the wattage rating to 1/2watt with the two 1/4watt, 69ohm resistors in parallel for an effective resistance of 34 ohms (note the color code on each resistor is for a 69ohm resistor which in parallel results in a nominal 34.5ohms.  I need to verify where that connector that Mc_Reatta's pigtail mod inserts to better understand what he did and how it precludes E026 errors. 

 

I will post a photo of the location of the connector in a few minutes.

[drtidmore]

Yesterday I shorted the "B" connection to grnd so as to see if I could get a pattern on when and under what exact conditions doing so would throw E026.  So far NO pattern!  I remember that came to this same conclusion when I last explored this issue and decided I was right on the edge of triggering the E026 which is why sometimes it triggered instantly, others it might takes miles and no pattern in the speeds involved other than it required SOME forward velocity.  If he is in fact simply connecting A to B the use of the resistors may be sufficient to limit the current enough to avoid tripping the E026 but still high enough to engage relays C&D.  Since we are dealing with TWO QDMs both have to be happy.  Lowering the current thru relay coils C&D would reduce the voltage that QDM2 (high speed) would see.  As I had already determined that A COULD ground B with no issues, I suspect that QDM1 (low speed) is happy regardless whether it is 1 relay coil or 3. 

Edited April 13, 2017 by drtidmore (see edit history)

[Ronnie]

This is the location of the connector C107 that Dave connected to (I think)..

 

 

[DAVES89]

That is correct. It is located directly under the relay center. Not hard to get to, or to install. And if for any reason you want to remove it you reconnect the original harness back together and the car is entirely stock again. 

 He was working on something else before he left, but I don't remember what it was. 

[Ronnie]

4 hours ago, drtidmore said:

Yesterday I shorted the "B" connection to grnd so as to see if I could get a pattern on when and under what exact conditions doing so would throw E026.  So far NO pattern!  I remember that came to this same conclusion when I last explored this issue and decided I was right on the edge of triggering the E026 which is why sometimes it triggered instantly, others it might takes miles and no pattern in the speeds involved other than it required SOME forward velocity.  If he is in fact simply connecting A to B the use of the resistors may be sufficient to limit the current enough to avoid tripping the E026 but still high enough to engage relays C&D.  

 

I don't yet understand how but I'm thinking the ECM is detecting an unexpected ground condition on pin B (telling it both low and high speed fans are running) when the jumper is installed without the resistor, and you are driving at speed. I don't know for sure, but I don't think the ECM would ever run the fans on high when ample air is flowing though the radiator at highway speeds. The reason it is hard for you to find a pattern is because it may also take into account engine temp and ambient air temp??

 

 

Edited April 13, 2017 by Ronnie (see edit history)

[2seater]

There is definitely a ground speed component to the fan operation and have found that in the chip, but I thought the speed was higher than 20mph in stock form? I have no idea how that may affect the testing but it appears the fans deactivate at some particular speed so may complicate the diagnosis?

[Ronnie]

6 hours ago, DAVES89 said:

I just went and stripped the heat shrink the rest of the way. It was a bare wire wrapped around the lead wire and "extra" solder as he wanted to be sure it was a good connection. Nothing else there but those two 34ohm resistors...

 

Thanks for cutting up your pigtail so we know what's inside that makes it work.

[Ronnie]

For the people with an '88 model - a pigtail like Dave's won't work. The fan controls are not the same as later models. If you want to run your fans on high whenever the low speed fan comes on all you have to do is install a jumper across the resistor shown in the photo below. I've had mine done that way for years with no problems. I intended to go back and do a little neater job on the installation but I never seem to get it done.

 

 

 

[drtidmore]

As I mentioned I had a paper design...well now it is implemented!  Spent yesterday afternoon building and installing.  Of course I had a few additional hours in working out the design and how to implement it.  Works perfectly, NO E026, totally adjustable high speed kick-in temp and soft fail back to the OEM functionality.  Retains the OEM fan relay's control of the actual fans but rearranges how their coils are controlled.  Only added a single new relay in the spare socket of the relay center in the mod, along with an externally mounted Hayden 3647 adjustable fan control module.  Then there was the rewiring.  ECM "A" and the low speed relay retain OEM configuration. The ECM "B" no longer connects to the OEM high speed relays but now grounds the new relay coil that is powered from the Hot-in-Run circuit.  The OEM high speed relay coils now have one side permanently grounded and both remaining coil contacts are tied to the wiper of the new relay.  The NO contact on the new relay is powered from the Hot-in-Run circuit.  The NC contact of the new relay connects to the fan output of the Hayden 3647 (i.e. +12 when the Hayden senses the trip temp).  The Hayden 3647 uses an electronic circuit with an adjustment range of 90-210 degrees to control a 30amp SPST automotive relay (socket would accommodate the more standard SPDT as well).  The release temp is always 10 degrees lower than the set temp.  The Hayden unit is powered from the switched side of the low speed relay (relay G pin1).  The Hayden 3647, thru the NC contacts of the new relay, connects to the OEM high speed fan relay coils, so when the Hayden switches on, the OEM HS relays behave the same as the OEM design for HS operation.

 

If the ECM should decide that it wants high speed, that functionality remains irrespective of the new controlling circuit state due to the fact that the ECM "B" output is now attached to the ground side of the new relay coil so if the ECM commands high speed fans, the new relay wiper will move to the NO contact which is powered by the Hot-in-Run circuit which will power up the high speed relays (this could happen if the AC refrigerant high side temp exceeds 169 degrees for example). 

 

The only real change to the OEM high speed relays is that unlike the OEM design where one side of the coils was powered by the Hot-in-Run circuit and then grounded by ECM "B", those relays are now permanently grounded and +12 is switched to them by the new relay thru either the NC or the NO contacts, both of which are powered by the Hot-in-Run circuit.  The ECM "B" is switching a standard automotive relay coil to ground so its associated QDM2 does not throw a E026. 

 

The Hayden was designed to handle up to 30amps but in this implementation it is switching ONLY relay coil current (milliamps).  I used the Hayden "ignition" lead to switch between OEM ECM logic or the new design.  If the "ignition" wire is switched to +12 volts the Hayden is in typical control of when high speed is activated (ECM still retains priority to activate however), otherwise the OEM ECM logic controls.  I used the Hayden AC compressor clutch detect input to control low/high or high only mode as when this input sees +12 it forces the Hayden to activate regardless of temp sensed. As the Hayden is powered via relay G pin 1 (i.e. low speed fan relay), if the ECM sees NO need for fans meaning that relay G is no activated, there is NO power to the Hayden, so NO FANS period.  Again, the ECM decides IF any fans are activated.   FYI, I powered both the switches for "ignition" (OEM ECM or Hayden control of HS fans) and the AC clutch detect (HS ONLY) from relay G pin 1 so that unless the ECM sees the need for fans (i.e. relay G active), NONE of the inputs to the Hayden are powered. The Hayden senses radiator temp thru a remote sensor slipped into the radiator fins close to the upper hose to best monitor the engine temp. 

 

With the exception of the wires to/from the Hayden, all the wiring was done underneath the relay center.  Thanks to the GM design, it is easy to remove contacts in the relay center so I repositioned several of the existing contacts where such was possible.

 

For my initial worst case testing, I switched the unit to high speed ONLY and proceeded to get the cooling system and engine heat saturated, with AC running, on the highway with ambient temps around 80, then I dropped off the highway to service roads and intentionally did a LOT of stop and go to see how the cooling system performed.  Typically under these conditions, I would have seen the coolant temp climb from 180 on the highway to 205-210 before the low speed fans could remove sufficient heat for the temps to drop back to the normal 180 (i.e. remove the heat soak).  With HS only mode engaged, the highest temp I saw was 182 and when fully stopped, the temps remained at or slightly below 180 (I am running a 180 degree thermostat), so this proves that HS mode with AC running is a LOT better at handling the heat saturated condition.   FYI, in city traffic only, only rarely does my Reatta heat saturate even though the fans are running on low but I have seen it climb into the lower 190s from time to time during extended stops.  It is the mixture of highway with sudden change to stop and go that gave fits to the cooling system.  I know that GM was totally content with this scenario and maybe on a brand new car, such was an acceptable design, but with a 28+year old car I just prefer to keep the temps at a more sane temp. 

 

FYI, my Reatta cooling system was chemically flushed, fitted with new radiator, new water pump, new hoses, RedLine Water Wetter additive, "Green" antifreeze,  and a 180 degree thermostat last fall. I also straightened all the fins on the condenser when I did the compressor replacement/conversion to R134a several years ago. 

 

Granted this mod was not plug and play and reversing, while possible, would take a few of hours to reconfigure the wiring, but I have retained ECM control modes of no fans, low speed fan, retained existing ECM high speed activation but now can override and set the high speed kick-in where I want.  I plan to set it at around 185-190.  I may run it in full time high speed mode over the summer and then come fall switch it back to low/high mode for fall and winter.  

 

If there is any interest, I will post the schematic of the original OEM design and then my modifications.  The use of the Hayden 3647 gave me additional functionality at a very affordable price of $34 as compared to a simply capillary tube thermostat at less than $20.  All in all, I have around $50 in this mod so one of the least expensive I have undertaken on the Reatta and it solves a gripe I have had for a long time.  

 

I still think Mc_Reatta's simple, always HS mode, plug and play mod is something that should be made available for those less inclined to rewiring in the relay center, but the mod I made was not rocket science either.   I have not had a chance to really dig into the how it might be preventing E026, but I will attempt to make some sense of Mc_Reatta's mod in the next week or so. 

Edited April 14, 2017 by drtidmore (see edit history)

[drtidmore]

Bit of a follow up.  Today the ambient temps were running the mid 80s and I had the Reatta out on the highway running between 75 and 80MPH for 20 miles or so.  The fans are still running in High Only mode.  While on the highway, the coolant temp never ventured above the normal 181 and on dropping off the highway and back into city stop and go, the temp momentarily did bounce to about 185, but quickly dropped to 180.  I am VERY pleased with the way the cooling system is performing with the fans running on high speed.  

 

My next steps are to adjust the set point on the Hayden to around 185 and see how the cooling system performs running in low/high fan mode.  Not sure exactly what set temp will work out to give the best results.  I will say that I am amazed at the increase in engine loading at idle that occurs when switching from low to high speed fan, so I know that running in high only does come with a penalty on fuel economy, but no idea how significant.

[DAVES89]

As the Red has Mc_Reattas mod and the Black doesn't I have always wondered why the gas mileage is different. Maybe that is why. The Black has always delivered better gas mileage.

[drtidmore]

12 hours ago, DAVES89 said:

As the Red has Mc_Reattas mod and the Black doesn't I have always wondered why the gas mileage is different. Maybe that is why. The Black has always delivered better gas mileage.

As I said, when I switched the fans in and out of high at idle there is a noticeable additional load from the alternator due to the fans.  It was surprising.  I guess I need to run the math and actually see the equivalent HP that the fan draw in low vs high.  

[89RedDarkGrey]

Let's hope you don't need new motors next

 

Cooling fan motors

[drtidmore]

4 hours ago, 89RedDarkGrey said:

Let's hope you don't need new motors next

 

Cooling fan motors

There are members on this forum that have been running the fans on CONSTANT high speed for 6+ years with no issues regarding either the cooling or the cooling fan motors.  With my setup, the fans kick in to high at 186 and then go back to low speed at 176.  As my Reatta runs a constant 180-181 on the highway, the only way it will reach 186 is in less than good airflow and as we go into the hottest weather if the coolant does not drop by to 176, I am fine with the fans staying on high as that will just ensure better AC performance.

[DAVES89]

As Mc_Reatta supplied me with these leads 6 years ago it must be me that you are referring to that have had the fans on constant high. I have had no problems with the fans wearing out but do have extra fans from cars that kdirk and I parted out so they were pretty much free. 

 Well worth it to keep our cars running cooler. As Padgett has said many times keeping the engines cooler is better for everything; wires, hoses, and sensors.

  

[Ronnie]

12 hours ago, DAVES89 said:

Well worth it to keep our cars running cooler. As Padgett has said many times keeping the engines cooler is better for everything; wires, hoses, and sensors.

 

I'm a firm believer in that too. My car has a 160 degree thermostat and a Hayden fan controller that cycles the fans on high at 190 degrees and back off at 176 degrees. It works great at cooling the engine when sitting in still in at traffic lights and the AC seems to work better under those conditions too.

 

I have discovered that the 160 degree thermostat has one drawback. It is too low for driving in cold weather. The engine has to reach 158-159 degrees to go into closed loop operation. At highway speeds in cold weather the 160 degree thermostat has a hard time maintaining that temperature.. That's not a problem for me because I rarely get my car out in cold weather. A 180 degree thermostat would be a better choice for most people.

[drtidmore]

3 hours ago, Ronnie said:

 

I'm a firm believer in that too. My car has a 160 degree thermostat and a Hayden fan controller that cycles the fans on high at 190 degrees and back off at 176 degrees. It works great at cooling the engine when sitting in still in at traffic lights and the AC seems to work better under those conditions too.

 

I have discovered that the 160 degree thermostat has one drawback. It is too low for driving in cold weather. The engine has to reach 158-159 degrees to go into closed loop operation. At highway speeds in cold weather the 160 degree thermostat has a hard time maintaining that temperature.. That's not a problem for me because I rarely get my car out in cold weather. A 180 degree thermostat would be a better choice for most people.

Ronnie, thanks for update on the 160 degree thermostat.  I have been pleased with the 180 degree thermostat overall.  

[89RedDarkGrey]

1 hour ago, drtidmore said:

 I have been pleased with the 180 degree thermostat overall.  

 

Me too