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AC troubleshooting - help!


fordrodsteven
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My apologies from the start. This may get to be a long story. This forum is the most informative / helpful site I've seen anywhere. Okay - so here goes. 1988 coupe... The car sat for a couple years. At one time there was some noise from the front of the engine when idling. I thought it was the belt tensioner. A while later (approximately a year - I didn't have the car on the road and just started it up every couple of months) I got a message for low freon pressure. A few months later whilst still trying to make her road worthy i took it to a dealership & asked them to get the AC working. They put in a new condenser (said it was leaking) then the mechanic said the compressor made a lot of noise as the belt was rubbing on the pulley. He said he pulled it out? I assumed he meant he pulled the clutch assembly a little away from the compressor to align the belt to quiet it. I thought to myself he should have fixed it correctly and pulling the clutch outward is not a good idea. I took it home and parked it.

Now here we are. I have got it on the road and passed inspection - Yay!! I have decided it's time to tackle the AC. The clutch will not actuate at all. I think now he meant that when he "pulled it out" that he disabled it somehow. I went though the procedure laid out in manual section 8A-62. It checks good except that the compressor never kicks in. All the results are what they should be otherwise. I went into diagnostics and the screen shows it is calling for the power to go to the compressor. I checked the relay socket to make sure I had juice there. I swapped out the relay for a known good relay. Now this may be where I am going wrong and I'm looking for some guidance. I connected a test light from the brown lead (at the compressor connection) and went to ground... the light did not go on. I think the brown lead is supposed to have 12V when the system is calling for the compressor. I also jumped directly from the battery (positive) to the clutch where the brown lead would connect and no result on the clutch. I plan to buy a ctuch / pulley assembly and change it out. I don't want to break it down to remove the compressor now that it seems to hold pressure just fine. I just want to make sure I'm getting a signal to the clutch to make it engage. Am I on the wrong track? The fan and heat all work as it should.

Edited by fordrodsteven
connected test light to brown lead at compressor connector (see edit history)
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Hi Ron,

I looked at the procedure. It says to disconnect the battery to clear the low freon codes. I plan to start there but just wanted to let you know that I checked the screen for error codes and there are none there to be cleared. I probably won't get to it until Sauturday. I'll post my results!

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Guest Mc_Reatta

Jumping 12v to the brown wire on the clutch should have made it click in. The black wire is supposed to be grounded all the time. Sounds like it isn't grounded or clutch is bad.

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I ordered a new connector lead for the clutch because mine was overheated and melted a little bit. I also ordered another clutch because I'm fairly certain the noise I heard before I brought it in and the noise he heard was most likely the clutch. I'll borrow a tool from the parts store and change out the clutch. Thanks for the note about the gap. I'll keep it in mind when going back together.

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here's a quick update. I got home and spent about ten minutes on it. I found the plug on the low pressure switch was not fully engaged. I suspect that is what the mechanic did to shut it down. any way I plugged everything back together after I found that. Started the car and still got no activity at the clutch when turning on the climate control. I pulled the plug off the clutch. It's really in pretty sad condition and I'm going to have to change it. I jumped a wire from the terminal (black wire side) on the clutch to ground and I jumped another wire from the terminal (brown side) to touch on the battery positive side. No action. I'm hoping my problem is a combination of the unplugged low pressure switch, the melted/burnt connector at the clutch and the clutch itself. When I get it back together I'll update.

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Guest Mc_Reatta

Definitely a problem with the clutch if it doesn't click when hit with voltage. Could just be gap is set way too wide or coil is shot. If you have a third hand, you could push in on it while the power is being applied to see if closing the gap will get it to kick in.

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I got a rebuilt clutch and a new terminal lead that I was going to change out on the end of the harness. First thing I did I worked on the connector. Turns out I found the diode in there!. I decided rather than screw around with the harness I would first try to refurbish what I have and recheck connections / continuity. Gat it all cleaned up and things are good. Next I went to re[place the clutch with a rebuilt that I bought. Turns out I don't have all the proper equipm,ent / tools readily available so I started messing with the unit that was already on the car. Did some cleanup and closed the air gap a little bit. I jumped wires to it and it snaps shut! I plugged everything in and started up the car. Still got no clutch engagement. I jumped a wire at the relay box and the clutch engages. Next I jumped a wire at the switch at the firewall (low pressure switch) and started the car. No engagement at the clutch.Now I need to figure out where to go next.

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The dealership recharged the system when they put in the new condenser. The mechanic told me afterwards that the clutch made noises he didn't like so he "pulled it out". I haven't had a low freon message for a few months now. Would the car still think it is low on freon? I have disconnected the battery and will go back to reconnect in a short while when I get back home to work on the car.

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Huh!? now I'm confused. When I reconnected I got three messages on the screen. Two were telling me it was because I disconnected the battery (B552 & C553) AND I got B448 for low freon. I guess a trip back to a shop for the A/C is in order. Maybe I should save my pennies and get it converted to R134A at the same time.

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  • 2 weeks later...

Well I've got it so everything except for the A/C is working. Cooler weather is coming and I will putting the car away for the winter. I'm going to hold off on the A/C issues until spring. I never changed the clutch because I was able to get the one on the car to engage. The reason it wouldn't engage before is because the air gap was too big. (Now I am reluctantly learning much about A/C - I usually just took the cars someplace for that type of work) Any way.... the clutch made a racket when it ergaged (could be the compressor). I will replace the compressor & receievr/dryer come springtime and get the system recharged. It has a brand new condensor in it right now from when I had it at the dealer 3 months ago. Should I change the orifice at the same time? Is it a good idea to convert to R134A also? So far my list for spring is four new tires and the A/C. Possibly change out the complete rear end suspension / axle at that time.

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Guest Mc_Reatta

You definitely want to replace the orifice tube along with the compressor and drier.

You might want to consider an upgraded variable orifice tube as well. Some swear by them, others say not worth it, but the theory behind it is sound. Should improve performance when engine is turning at low (<1500 RPM) or so

Converting to R134a is not a given. If R12 is available to you at reasonable cost, staying with it is probably the best decision. While R134a costs less (not so much anymore) it requires purging the system of all the old oil so the bottom line price difference is a wash most times. R12 will give best performance as it's what the system was designed for, but a proper conversion is plenty cold enough even in the harshest environs.

Just hope when you finally get it looked at, the compressor has self destructed causing the condition known as "black death" That increases the cost to repair significantly.

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  • 1 year later...

Well. Here I am almost 2 years later. I spent all of last summer building a new 45 X 28 garage. 2 months ago I took the car to have the compressor replaced and convert to R134A. After many excuses and waiting for a part here and a part there it is together and holding pressure. They replaced the compressor, condenser, reciever dryer, orifice and low pressure switch. The technician finally gave up. He cannot get the compressor to engage. They are telling me that they suspect the BCM. I brought the car home to take a shot at it myself. I went into the diagnosis screen and it says it's calling for compressor. (it lights up the little triangle above COMP). When I cycle through heat, econ, defr. they all seem to work okay. The COMP triangle lights up at the appropriate times and is off at the appropriate times. I noticed that the triangle with AC never lights up though. I checked for continuity at the three switches. (Low Pressure, Low Temperature and High Temp.) they all check as closed (zero ohms). I tried putting a jumper on the low pressure switch to see if it would engage the clutch -  no luck. Then my wife called me in for supper. I think next I'll try jumping it at the A/C relay to see if the clutch will engage from there. I'm still looking through my FSM trying to find a solution.

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thank you 2reattas. I disconnected the battery and jumped wires to the clutch to insure it would engage. I reconnected the battery and cleared codes. It appears that the dash interface is working correctly. Now I guess I'll be checking all the connections and for harness continuity on all the different switches and sensors used in the circuit..

Edit update; I changed out fuse #19 - no change. I did notice that when I went into diagnostics mode that under BCM it is calling for compressor but under ECM it is not calling for compressor. At least it's not really too bad to work on. I enjoy the car! My wife wants me to get it sorted so we can take some leisurely drives in it.

While I'm at it I think I'll check those connections under the passenger seat also!

Edited by fordrodsteven (see edit history)
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If you have power out of the low pressure switch then the next thing I'd check is the clutch ground. The AC clutch pulls about 10A so may look fine on a meter and fail when engaged.

 

I'd also look at BD 27 (High side) and 28 (low side) & BI08 (low refrig switch.).

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Thank you guys for all your help & suggestions. I tried all the things from your comments and I also worked through the issue with help from Ronnie at the Reatta owners Journal website. He compared troubleshooting readings on his '88 with my '88. Turns out everything seems to check accurate. When I used the FSM diagnosis chart it walks me down to a finding of a faulty ECM. I don't have a spare so I ended up buying one. I'll update back here when I get the ECM installed and see what happens.

 

Another thing I found was that now the lower transmission cooling line is leaking. The line was rusted and probably porous. I'm guessing the techinician pushed it out of his way when he was removing the old compressor and caused it to leak. Anyway. I ordered new lines (upper & lower) from thewrenchmonkey.ca I Canada. They are manufactured by Dorman.  I'll be replacing those lines also while I'm working the AC issue.

Edited by fordrodsteven (see edit history)
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63 Viking. yes I checked the relay and to be sure I swapped in four others to verify that the problem was not the relay. I used the diagnosis tree in the manual (page 1C-19 chart 2 "compressor won't engage") I ended up at the statement that says to replace the ECM so that's what is next.

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Handmedownreatta - I jumped it directly at the compressor and it kicks on. I also jumped it at the relay as per the diagnosis chart A instructions. the compressor engages when I jump 12V to it.

 

Well crap! I got the replacement ECM today. I changed out the chip and put the ECM up into the hole. Hooked it all up and having same issue. Compressor does not engage. I got frustrated and decided to look at it again later. I'm going to run through the full troubleshooting procedure right from the very start to see if anything reads differently. Probably Friday. I have a few things to do on Thursday. On the brighter side I repaired four connections on the wires under the seats. I now have working courtesy lights on the doors!

 

I'm thinking Padgett might be onto something and I'm going to check compressor ground first! Although I  would think my ground is good because it engages just fine when I jump it up at the relay.

Edited by fordrodsteven (see edit history)
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Agree. Also you said if you jumper at the relay it kicks in so not the compressor ground but may be the relay ground.

 

Looking in my FSM the realay should have power from fuse 19 on pin 4 and power on pin 2 from the low pressure relay (and if the realy is open (low pressure) you should be getting a BCM error.

 

The othe part is that when the ECM commands AC you should get a ground from the ECM on pin 5 of the AC relay and 3C15 of the ECM. If you swapped ECMs and AC is on and are not getting ground to the relay coil then I suspect you have a bad wire (762 Dark  Green/Yellow) possibly at the bulkhead bulkhead connector.

 

I'd start by grounding Pin 5 on the relay with the key on and see if the ac clutch plate goes "click".

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I have been trying to help fordronsteven with his AC problem and here is what I have observed. Maybe someone will spot something we have overlooked.:

 

On his BCM diagnostics screen the COMP triangle is illuminated indicating it should be sending a signal to the ECM requesting the Compressor to run just as it is on my '88.  Could that signal be getting lost between the BCM and ECM preventing the ECM from energizing the compressor? If so how could that be tested?

 

He confirmed that his AC relay is getting power to the coil and to the contacts as it should. He has swapped out the relay several times to make sure it is in good condition.

 

He confirmed the TPS, Power Steering Switch and Coolant Temp were all in good working order. If the ECM senses either of those items are out of normal range it will disengage the compressor. After a lot of testing we could only conclude his ECM was bad and not grounding ckt. 762 which would pickup the AC Relay.  After he installed a replacement ECM it has the same symptoms as the old ECM.

 

He cannot energize the AC Relay (clutch) using ECM overrides in diagnostics that should bypass the items mentioned in the previous paragraph. I can energize the compressor using ECM overrides in my '88

 

There might be a bad connection or broken wire on ckt. 762 but the odd thing is the COMP triangle on the ECM diagnostics screen is never illuminated indicating that the ECM is trying to energize the AC Compressor relay. On my '88 the ECM COMP triangle illuminates anytime the compressor is running. 

 

 

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I am confused here:

"On his BCM diagnostics screen the COMP triangle is illuminated "

" the odd thing is the COMP triangle on the ECM diagnostics screen is never illuminated "

 

These cannot both be true. The indicators (triangles) are the same in both screens.

Edited by padgett (see edit history)
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When I asked if the COMP triangle was illuminated here was his response on ROJ:

 

Quote

I just edited my other response before I saw your question. Under ECM diagnostics the comp triangle is not lit. Under the BCM diagnostics the comp triangle is lit.
By the way- Thank you very much for your help.

 

Padgett, I wish you would read though our conversation here and see if you see anything that we have not covered in our effort to get his AC compressor to kick in.

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OK now I understand. The comp triangle on the ECM page is not the same as the comp triangle on the BCM page. The issue is that the two modules are talking to each other on the serial link and that appears to be how the BCM tells the ECM to turn the compressor on. Since we can look at both through the CRT via the serial bus that the BCM would be sending a Compressor turn on command that the ECM is not receiving does not make sense.

 

First thing I'd do is to instrument the relay lines so that I know for sure if pin 5 is being grounded by the ECM and, if not, does grounding pin 5 turn the compressor on ?

 

ps just tried ED06 and in a quiet garage with hearing augmented I hear the clutch "click" when change to 99.

Edited by padgett (see edit history)
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33 minutes ago, padgett said:

The issue is that the two modules are talking to each other on the serial link and that appears to be how the BCM tells the ECM to turn the compressor on. Since we can look at both through the CRT via the serial bus that the BCM would be sending a Compressor turn on command that the ECM is not receiving does not make sense.

 

 

Is there a place in diagnostics that shows if a comp turn on signal is being sent/received from the BCM to the ECM? Even if the ECM gets a turn on signal from the BCM it still can keep the compressor off if certain conditions are not met but we couldn't find any reason for it to hold the compressor off. Thanks for your help!

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Quote

Padgett wrote: First thing I'd do is to instrument the relay lines so that I know for sure if pin 5 is being grounded by the ECM and, if not, does grounding pin 5 turn the compressor on ?

 

ps just tried ED06 and in a quiet garage with hearing augmented I hear the clutch "click" when change to 99.

I didn't instrument the relay lines but. I have been able to jump from pole 4 to pole 1 and the clutch energizes. I have jumped from pole 2 to pole 1 and the clutch energized. I read this. I put the relay back in. I jumped pole 5 to ground and the clutch energized. When I try to turn on the AC through the climate control system the car still does the same thing. No engagement of the clutch. I still have the same situation where in diagnostics I can see the comp triangle lit up under the bcm screen and not lit when in the ECM screen.

 

I disconnected the battery again. Hooked it up. Cleared B554 and C553 codes. I went through the A/C temp sensor troubleshoot procedure from the "ROJ" Readings were as follows; ED04 - 20, ED23 - 20, BD21 - 20, BD25 - 23, BD26 - 22, BD27 - 23, BD28 - 21, BD32 - 40. The only breading that was off more than a couple degrees was BD32 Sunload. It checked 40degrees. Does that signify anything that might be causing my problem?

 

Opps. I have to go now. My bride (41 happy years together) and I are going out to dinner with some relatives who are in from Michigan.

ALSO - Thank you very much to all of you guys for your help. I'm sure this will get sorted out. BTW - I also have run an alternate wire (spliced Dark green with yellow tracer) from the ECM to the compressor relay. and still having same issues.

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Given all that has gone before there is only one thing not checked and that is the ground that the ECM is supposed to apply to the AC relay.

 

The 253 schematic is at http://www.exatorq.com/ludis_obd1/1228253schematic.html and I am going to try to make sense out of it but looks like when the ECM turns the AC relay on (ECM plug Orange Yellow C15 should the to the AC relay)

When the AC relay is energized  then EO08 should change from HI (off) to LO (on).

What is the PROM ID (ED99) ? Grasping at straws but maybe it has the wrong PROM.

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Okay. I just got back from another night out for dinner with family. (I'm just trying to do my part for the economy :)). Any way I read this earlier today and got to work on the car for about an hour. I pulled out the battery and took apart the three different ground connections. There was no corrosion. I cleaned everything and re-assembled. I cleared the B554 and C553 codes. I checked the PROM number under ECM diagnostics it says ED99 and under BCM diagnostics it says BD99. I jumped pin 1 to pin 4 where the A/C relay plugs in and the clutch engages. I jumped Pin 1 to pin 2 and the clutch engages. I put the relay back in and jumped pin #5 to ground The clutch engages for about 2 seconds. I still have an alternate wire installed to bypass the dark green with yellow tracer from the ECM to the A/C relay. I started the car up and I still get the same situation where in diagnostics the COMP triangle does not light up in ECM diagnostics and it does light up in BCM diagnostics. The A/C still does not work. Tomorrow I plan to attempt those other things Padgett suggested. I will try to get the cooling fans to come on (EO07) and I will check for relay energized(EO08).

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