need AC help

[heygibb]

My AC isn't dependable. Sometimes it cools and more recently, it doesn't. I had the system changed over to R134a probably 15 yrs ago or so and have topped it off a few times since then.

Before buying more refrigerant, I decided to check my system pressures. I don't have a set of gauges so I used the gauges I've saved from previous doses of R134a.

The ambient temp is 92 degrees.

With the AC off, compressor not running, the psi is around ~115-120.

With AC on, compressor running, accumulator frosty, the psi is ~55. That seems to fall into the "charged zone" on these gauges.

So, I'm not sure what to do. I don't want to overcharge my system. Is there another component I need to look at?

 

Thanks

 

 

[Ronnie]

It looks like the pressures are in the right range.  What is the temperature coming out of the vents?  Is the compressor cycling on and off a lot?

[heygibb]

It isn't cooling at the moment. I used one of those laser temp sensor guns and it reads 94 degrees. I'm not sure how accurate that would be since I only let the AC run 5 mins or so. I guess I need to let it run for 1/2 hour or so to get the surface of the duct acclimated to the air temp the AC is producing. The comp does not kick on and off, as you say. The fan is working as it should, too, if that matters.

[Ronnie]

31 minutes ago, heygibb said:

It isn't cooling at the moment. I used one of those laser temp sensor guns and it reads 94 degrees. I'm not sure how accurate that would be since I only let the AC run 5 mins or so.

 

After 5 minutes you should have seen the temp of the air coming out of vents going down quite a bit.  A thermometer that can be slid into the vent would be much better for checking the AC temps.   You should also be able to feel the low side lines at the accumulator starting to get cold and have condensation on it after a few minutes if the compressor is running. Let the AC run 10-15 minutes and see if those parts are getting cold. If they are getting cold enough to sweat and the air coming out of the vent isn't getting colder, check the temp valve rod to make sure it is moving all the way to the cool position.  HVAC Blend Door Motor Troubleshooting

 

 

 

 

[Barney Eaton]

On R12,  the low pressure translated almost directly to the temp of the system.......you wanted it as close to freezing as possible but lower will frost the evaporator and you clog the airflow.

134 is slightly different and I don't have a chart here but......it is close,  so your low side should be in the 38-40 psi range to get good cold air.

I would add more 134 shooting for something at 40 or a little below.

[B Jake Moran]

1 hour ago, Barney Eaton said:

On R12,  the low pressure translated almost directly to the temp of the system.......you wanted it as close to freezing as possible but lower will frost the evaporator and you clog the airflow.

134 is slightly different and I don't have a chart here but......it is close,  so your low side should be in the 38-40 psi range to get good cold air.

I would add more 134 shooting for something at 40 or a little below.

That is a good guideline.  Is there any way you can add some dye to the system.  Then run it after adding some R134a.   See if your temperatures recover then with the dye in you can see where it might be leaking. 

[heygibb]

I just saw Barney's earlier post re the temp valve control rod. I think that is behind glove box...correct?

I just tried the AC w/ a digital meat thermometer in vent by driver. I ran AC for 15 mins.

start temp   94
5 min   105
10 min   114
15 min   118

The accumulator gets cold and wet with condensation quickly. It doesn't get "frosty" as I stated earlier...just cold.  If the compressor was bad, would that happen?

The psi was pushing 60 w/ AC on, full blast.

I'll check that rod movement and plan on adding refrigerant, after that.

I

Edited July 23, 2019 by heygibb
give credit where credit due (see edit history)

[heygibb]

2 minutes ago, B Jake Moran said:

That is a good guideline.  Is there any way you can add some dye to the system.  Then run it after adding some R134a.   See if your temperatures recover then with the dye in you can see where it might be leaking. 

If I'm not mistaken, some 134a can be bought w/ dye. It's been a while since I needed any so I'm not sure on that. I'll check into it.

[ChrisWhewell]

When you go by over the a accumulator with compressor running, one of the pipes should be cold.   On a good system, get a feel by the hand of about how cold it is.    Then, if your system is running, feel that tube and make a judgement.    Bottom line, does it keep you cool when stopped at traffic lights ?  It looks like Barney's message above is right on too.

[heygibb]

2 hours ago, Ronnie said:

 

After 5 minutes you should have seen the temp of the air coming out of vents going down quite a bit.  A thermometer that can be slid into the vent would be much better for checking the AC temps.   You should also be able to feel the low side lines at the accumulator starting to get cold and have condensation on it after a few minutes if the compressor is running. Let the AC run 10-15 minutes and see if those parts are getting cold. If they are getting cold enough to sweat and the air coming out of the vent isn't getting colder, check the temp valve rod to make sure it is moving all the way to the cool position.  HVAC Blend Door Motor Troubleshooting

 

 

 

 

The rod doesn't move. I tried AC, bilevel, heat...no movement. It is stationary in the position you show in this picture. It looks fully extended.

 

Edited July 23, 2019 by heygibb
move quote (see edit history)

[heygibb]

33 minutes ago, ChrisWhewell said:

When you go by over the a accumulator with compressor running, one of the pipes should be cold.   On a good system, get a feel by the hand of about how cold it is.    Then, if your system is running, feel that tube and make a judgement.    Bottom line, does it keep you cool when stopped at traffic lights ?  It looks like Barney's message above is right on too.

Both lines attached to accumulator are cold, as is the accumulator. They get cold almost immediately after turning on the AC, w/ condensation.

I had to block hot air coming from fan blowback to get a reading w/ my laser thermometer so it probably isn't too accurate. It read 74 degrees. It feels colder than that to the touch...like a cold canned drink would feel.

[Barney Eaton]

If your pressure is not down around 40 you need more 134.

That temp control rod is actually a BLEND control.......it moves a door to blend hot and cold air,  so the rod not moving is not your total problem.

When you want it cold in the car,  the blend door should shut off hot air from entering........same thing when you want it warm in the car,  it allows more warm air to be routed into the cabin.

Here is a link to lots of temp/pressure charts for R134

https://www.google.com/search?q=r134a+temperature+pressure+chart&tbm=isch&source=hp&sa=X&ved=2ahUKEwiYvKi7oszjAhUDNKwKHWLpB7QQsAR6BAgFEAE&biw=1920&bih=931#imgrc=Uy3_xZmDu9qPsM:&spf=1563927524705

One thing not mentioned is a evaporator that is partially plugged with contamination on the outside......even when the pressure is correct, you will not get airflow into the cabin.

[Ronnie]

6 minutes ago, Barney Eaton said:

That temp control rod is actually a BLEND control.......it moves a door to blend hot and cold air,  so the rod not moving is not your total problem.

 

Barney I don't follow your assessment of his problem not being the blend door.

 

34 minutes ago, heygibb said:

The rod doesn't move. I tried AC, bilevel, heat...no movement. It is stationary in the position you show in this picture. It looks fully extended.

 

 

It sounds to me like the blend door is staying in the heat position.  Everything on the cooling side seems to be working correctly.

 

1 hour ago, heygibb said:

I ran AC for 15 mins.

start temp   94
5 min   105
10 min   114
15 min   118 

 

The blend door being stuck in heat mode explains those readings with the temperature increasing. Maybe Barney is right and the blend door isn't the problem but if you disconnect the rod and move the door actuator arm to the left you will quickly know if that is the problem.

 

[heygibb]

1 minute ago, Ronnie said:

 

Barney I don't follow your assessment of his problem not being the blend door.

 

 

It sounds to me like the blend door is staying in the heat position.  Everything on the cooling side seems to be working correctly.

 

 

The blend door being stuck in heat mode explains those readings with the temperature increasing. Maybe Barney is right and the blend door isn't the problem but if you disconnect the rod and move the door actuator arm to the left you will quickly know if that is the problem.

 

I'll try that.

 

23 minutes ago, Barney Eaton said:

If your pressure is not down around 40 you need more 134.

That temp control rod is actually a BLEND control.......it moves a door to blend hot and cold air,  so the rod not moving is not your total problem.

When you want it cold in the car,  the blend door should shut off hot air from entering........same thing when you want it warm in the car,  it allows more warm air to be routed into the cabin.

Here is a link to lots of temp/pressure charts for R134

https://www.google.com/search?q=r134a+temperature+pressure+chart&tbm=isch&source=hp&sa=X&ved=2ahUKEwiYvKi7oszjAhUDNKwKHWLpB7QQsAR6BAgFEAE&biw=1920&bih=931#imgrc=Uy3_xZmDu9qPsM:&spf=1563927524705

One thing not mentioned is a evaporator that is partially plugged with contamination on the outside......even when the pressure is correct, you will not get airflow into the cabin.

Thanks for the link. I'm getting good air flow in the vents but good to keep evaporator blockage in mind in future.

[DAVES89]

If your clip that holds the rod is broke, just go to the "Helps" section in the local "FLAPS" and look for the rod clip that goes in the door for the lock arm. It is the same size. 

[heygibb]

You guys are spot on, as always.

I disconnected the rod clip and moved it to the left. Voila...cold air. After 10 min, the vent temp bottomed out at 56 degrees. Car interior cooled down real nice.

The psi reading was 43, after dropping from almost 60 as soon as I moved the rod. So the charge is within the prescribed level, according to this chart. I have 80 degree ambient temp. Anything between 40--50 is called for.

So, two questions

1- Is there a fuse/relay that controls the device that actuates the rod? What is the next step in that area?

2- Would you top off the system with more refrigerant? I'm leaning toward getting it down to 35.

[DAVES89]

Check the vacuum lines in the engine compartment. Maybe you will be lucky and the line is either disconnected or broken.

[Karlw144]

If you add more refrigerant, the pressures will not go down. If you didn’t have enough refrigerant, you’d have the compressor rapid cycling and the head pressure would be low. Everything I see points to the blend door being the problem. My 2 cents worth. 

[2seater]

As pointed out, the hvac controller is vacuum operated except for the blend door, which is an electric stepper motor. If it was stuck, perhaps readjustment will cure the problem but if it doesn't move when commanded, it may need repair or replacement. 

[DAVES89]

1 hour ago, 2seater said:

As pointed out, the hvac controller is vacuum operated except for the blend door, which is an electric stepper motor. If it was stuck, perhaps readjustment will cure the problem but if it doesn't move when commanded, it may need repair or replacement. 

 

 I had a problem with my controller on the Black not working, so I disconnected it and removed it from the car. I tried it again while it was in my hand and it started working. So I reinstalled it and it has worked ever since.

 I marked it up to the "gremlin" that sneaks into my garage every so often to mess with me...

[heygibb]

re all

I'm convinced refrigerant level is fine from what you are saying, and the chart. So I'll leave it alone. It tells me I don't have a slow leak somewhere, which is good.

It's the controller/motor that is the problem. My blend door rod is in the extended HEAT position. It doesn't move when I activate the AC, but I can feel it try to move when I place my finger on top of the pivot arm. So it is getting the current it needs.

I dropped my 1/4" universal/torx down in the cavity while trying to extract the rear screw so, to retrieve it, I had to remove the lower covering of that area. I thought maybe I'd remove the motor and see if gearing is degraded, but unplugging the harness isn't easy. Is there a technique other than a methodical pulling motion, to get wiring connector off the unit?

If it's the vac line causing the hiccup, that would be great. I think that is a good possibility since I feel the motor trying to engage. I can see where the vac line is attached. I'll inspect that connection and then check under the hood.

[Ronnie]

I would get the blend door problem fixed first - but If the AC isn't cooling properly after you get the blend door working properly adding more Freon may not help. 

 

The Reatta has a low side temperature SENSOR that is used to regulate the evaporator temperature by signaling the BCM to turn the compressor off and on to keep the evaporator from freezing up. If that sensor goes bad (mine did) the air coming out the vent will be cool but it won't get as cold as it should no matter how much Freon you add to the system.

[heygibb]

39 minutes ago, Ronnie said:

I would get the blend door problem fixed first - but If the AC isn't cooling properly after you get the blend door working properly adding more Freon may not help. 

 

The Reatta has a low side temperature SENSOR that is used to regulate the evaporator temperature by signaling the BCM to turn the compressor off and on to keep the evaporator from freezing up. If that sensor goes bad (mine did) the air coming out the vent will be cool but it won't get as cold as it should no matter how much Freon you add to the system.

That is my intent. As cold as the interior got last night, I think I'll be ok Freon wise.

Since I can feel the motor try to engage with my finger on the rotating part, (there is a slight click/movement) does that mean the vacuum input is already present? Is the vac involvement necessary for power to be sent to motor?

Or does power get sent to motor, and then, the vac input activates the arm movement? Knowing that would be a way of discerning if vac line is intact, if I can't find it's compromised. I hope that makes sense.

[heygibb]

One other thing, does the B440 code only tell me the door isn't responding to commands or does it specifically identify the cause? I think I know the answer but thought I'd ask.

[Ronnie]

With the engine running, are you able to change from the main vents to the defrost vents and feel the air coming out at the different locations? If so the vacuum part of the HVAC controller are working.   I'm not an expert on this but I don't believe vacuum has to be present for the electric stepper motor to move the blend door rod.

 

3 minutes ago, heygibb said:

One other thing, does the B440 code only tell me the door isn't responding to commands or does it specifically identify the cause? I think I know the answer but thought I'd ask.

 

I -believe- the code B440 is set when the stepper motor doesn't move the door to the position commanded by the BCM but I don't know that for sure.

[Barney Eaton]

 

I do not claim to be an A/C expert,  but what bothers me is in the early post the low side never read below 50 psi.  but when you moved the blend door to get cold air,  the pressure dropped to 43

I would think the low pressure side would not vary that much just by changing the position of the blend door.

 

On the A/C controller that moves the blend door..........the ones from a Riviera are the same ....so if you are looking for a replacement in a pick-n-pull they are more plentiful than Reatta.

What I would like to know......is the controller in other GM cars of the period the same?   I know the outside housing is different so I did not pull one from an Eldorado,  but after thinking about it

I suspect the board inside the housing may be the same and the housing is different to be able to mount it in different cars.

The logic being.......why would GM build several different controller board?    Just use the same board assembly and change the housing

If anyone frequents pick-n-pulls it would be interesting to determine if the boards are the same.......that would give us many more GM cars to find the part.

Edited July 24, 2019 by Barney Eaton (see edit history)

[heygibb]

Yes on the different air locations working...defrost, bilevel, etc. Good to know re vac line.

I'm going to try and remove the motor and look inside. I can't be any worse off w/out it. I can position the control lever for AC and get by during the hot months.

[Ronnie]

2 minutes ago, heygibb said:

I'm going to try and remove the motor and look inside. I can't be any worse off w/out it. I can position the control lever for AC and get by during the hot months.

 

You might be better off just finding a complete used controller. If you screw up the electrical board in the controller you could end up with air only coming out the defrost vents, which is the default position of the climate controls.  Keeping the blend door in the cool position is a good idea until you can find another controller.

[heygibb]

Here are some pics of inside the controller. I haven't looked at wiring diagram but I'm surprised there is voltage to motor by default, before AC turned on. Does that indicate problem upstream from motor or does the locked up motor prevent the power feed from returning to 0 v? Maybe I'm misreading the info.

I'll end up replacing whole thing eventually, but I was thinking of replacing the motor only. If the problem isn't just the motor, I'd be wasting my time.

Anyway,...

ignition on ACC   no voltage at motor

Ignition on, no start   4.8v at motor

Ignition on, start engine, AC OFF   6.39v

Ignition on, start engine, AC ON   6.39v

 

Barney, I turned AC on and cycled the door several times. Today, the psi is 45, steady, whether door is open or closed...no difference in pressure.  I must have misread gauges last night.

[Ronnie]

Perhaps there is a default position that the BCM tries to move the door to - even if the AC is off.  Go into diagnostics and look at BD22 (Commanded Air Mix Valve Position) and BD23 (Actual Air Mix Valve Position).  They should match if the BCM is satisfied that the door is in the proper position.  According to the FSM the BCM gets feedback from a potentiometer mounted on the motor to determine what the motor is doing.  The 6.39 volts you are seeing might be the BCM trying to move the door into the proper position even though the AC is off.

[DAVES89]

If you do a search using "controller" and using 2seater as the author you will have a great explanation. He did exactly what you are doing less then 2 years ago.

[2seater]

6 minutes ago, DAVES89 said:

If you do a search using "controller" and using 2seater as the author you will have a great explanation. He did exactly what you are doing less then 2 years ago.

'Tis true Dave. The motor itself just unplugs from the board and is a complete bolt in, so it could possibly be salvaged from an otherwise junk controller. Of course that assume the board is talking to the motor properly. From the description it sounds like everything works except the blend door motor. Does the door stick, is the motor bad or is the board bad, all possible issues. Not uncommon for the plastic retainer to break, at least partially, on the left hand side where it attaches to the door arm.

[heygibb]

12 hours ago, 2seater said:

'Tis true Dave. The motor itself just unplugs from the board and is a complete bolt in, so it could possibly be salvaged from an otherwise junk controller. Of course that assume the board is talking to the motor properly. From the description it sounds like everything works except the blend door motor. Does the door stick, is the motor bad or is the board bad, all possible issues. Not uncommon for the plastic retainer to break, at least partially, on the left hand side where it attaches to the door arm.

Thank you for clarifying my point. I found sources for the motor here, http://oemcats.com/oem-parts/16144370.html , assuming the links are active. It is a simple plug and play deal, once you access the device. I haven't read through your previous thread on this yet, but Ronnie's explanation on the voltage reading sounds plausible. It would lead me to believe replacing the motor only, would be the fix. I was concerned about the existing voltage being a problem, and by extension, the board itself. Chances are, the board is good.

My door works easily and, you are right. The connector on the left end of the rod has been compromised by part of the locking mechanism breaking off due to the brittle nature/age of it. Once I replace the motor, I'll address that. As of now, I have the rod secured with a small cable tie, in the full AC position.

[padgett]

I haven't seen anyone mention needing a good supply of air through the coils. I use an earlier one of these when tuning an AC. Also the low side pressures I am seeing here are too high. I like to see 25-35 psi on the low side when working properly. Do not want it going under 20 because it will cycle.

 

Have seen that blend door servo stick before but usually a few cycles from max cool to max heat and back will free up (a drop of 3-in-1 oil at the bearing won't hurt).

[harry yarnell]

30-35 psi with R 12;

42-46 for R134.

That's the very basics. PERIOD.

[padgett]

Around here I shoot for above 25 and not cycling at 2k rpm. That keeps me cool in Florida (just have one with R12, rest have 134).

[Barney Eaton]

Have you seen any of these videos?    I know a guy that has been using it in his 1956 Buick for several years.

 

[padgett]

errr Barney, this guys apparently does not know the difference between CFM and microns (vacuum) and has some really cheap equipment. I do use the green clamps though. He only purged the feed line ? Have heard of DustOff being used as a refrigerant but has nasty side effects.

[Ben Bruce aka First Born]

What are the nasty side effects, Padgett?

 

  This is what Willie uses, isn't it, Barney?

 

  I am thankful for the "hang under the dash" simplicity of the system I installed in the '50.

 

  Ben

Edited July 26, 2019 by Ben Bruce aka First Born (see edit history)

[Ronnie]

Getting the best cooling with the Reatta Climate Control system isn't just about getting the pressures right.  I use this method after I get the pressures right to get the best cooling and it works well  AC System Fine Tuning