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1992 Cadillac Sedan DeVille 4.9L (Deceased), 1991 Cadillac Sedan DeVille 4.9L
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103 Posts
Discussion Starter #1
Man, I've been having a lot of car trouble lately! The problem at hand is the A/C working intermittently. The fans function normally, but it doesn't always blow cool air. There's no real pattern to it. Sometimes I start the car and it's not working; Other times it works for a little while, then stops working, then starts working again all in the same trip.

The only thing that might help diagnose it is that when it's hotter out it is more likely to not work. Here in FL, it's around 90 degrees in the afternoon and stops working often. At night, it's 80 degrees and usually works fine. I have the A/C set to 60 degrees and no matter how hot it is outside, when it does work, it's ice cold.

Any help is much appreciated!
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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68,518 Posts
Got a local automotive A/C shop that can do a running refrigerant pressure (high/low) check ? You might get lucky with a simple quick charge of several ounces of - 1992 ???? - R12 or r134a ????
 

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Registered
1992 Cadillac Sedan DeVille 4.9L (Deceased), 1991 Cadillac Sedan DeVille 4.9L
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103 Posts
Discussion Starter #4
I'm very sorry for the delay! I have no codes to report.

I guess I should check the charge first, although I had it filled last year when I got a new Compressor, Dryer, and Orifice Tube.

Here's my next question: Would you recommend using the cans (like A/C Pro) to check and, if needed, top off my refrigerant? I have never used them before, but have heard that they're good if you just need to add a little bit.
 

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Master of the Dark Art of Diagnostics
2003 DHS - two-2002 DHS, 2003 SLS, 1995 Sedan DeVille, 1989 Coupe DeVille
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19,289 Posts
I'm very sorry for the delay! I have no codes to report.

I guess I should check the charge first, although I had it filled last year when I got a new Compressor, Dryer, and Orifice Tube.

Here's my next question: Would you recommend using the cans (like A/C Pro) to check and, if needed, top off my refrigerant? I have never used them before, but have heard that they're good if you just need to add a little bit.
==========================
this - from post #1 -
when it does work, it's ice cold.
so freon is NOT your problem -

the A/C working intermittently.
The fans function normally,
but it doesn't always blow cool air

I suspect a vacuum leak/problem -

your system is all vacuum operated -

without an adequate vacuum supply -
the system is not going to operate correctly -

does the auto-release parking brake work?
it shares the same vacuum circuit -

Would you recommend using the cans (like A/C Pro)
to check and, if needed, top off my refrigerant?

NO - NEVER -

you can buy a QUALITY AC gauge set for less than $60 -
that will give you the actual pressures of BOTH the high side and the low side -
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
Here's my next question: Would you recommend using the cans (like A/C Pro) to check and, if needed, top off my refrigerant?
If you don't have a set of gauges, check the inlet and outlet A/C lines in the firewall. They should both be cold and the same temperature. If so, you most likely do not need a refrigerant charge.
 

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Registered
1992 Cadillac Sedan DeVille 4.9L (Deceased), 1991 Cadillac Sedan DeVille 4.9L
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103 Posts
Discussion Starter #7
New Information: An old problem I had seems to have resurfaced. Sometimes the compressor will randomly shut off and then the AC starts blowing in the hot humid air from outside, but then the compressor won't turn back on. However, if I tap the ground wire underneath the car, on the lower front passenger side, (I think it's the ground to the AC low pressure switch) it kicks back on. I had this wire checked and re-secured about a year ago, but I guess it's vibrated loose.

Other than that, I had the car idling for 20 mins in 90 degree weather and the AC ran fine the whole time. When I was driving to work in the same weather, it only worked for about 5 minutes. I don't know if I have a vacuum leak as well, since my auto-release doesn't work (It hasn't for years). However, I think my first objective should be to secure that damn ground wire.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
Try pulling the vacuum line off of your parking brake release and plug it with a screw, wood dowel, tape or whatever. That will bypass the parking brake release diaphragm in the event that is where your leak is. Does that solve your problem? If so, either leave it like that or replace the diaphragm.
 

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Registered
1992 Cadillac Sedan DeVille 4.9L (Deceased), 1991 Cadillac Sedan DeVille 4.9L
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103 Posts
Discussion Starter #9
Try pulling the vacuum line off of your parking brake release and plug it with a screw, wood dowel, tape or whatever. That will bypass the parking brake release diaphragm in the event that is where your leak is. Does that solve your problem? If so, either leave it like that or replace the diaphragm.
I plugged it with a screw a while ago when I noticed it wasn't working. It probably won't be until next weekend, but I'm going to check that ground wire as well as the vacuum pressure. I'll keep you guys updated.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
Not to be nit picky, but technically vacuum is a lack of pressure. Anything below atmospheric pressure becomes a vacuum.



Class dismissed.
 

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1985 Fleetwood 75
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345 Posts
Replace the engine coolant temperature sender and re crimp the connector or install a new connector on engine temp sender. The BCM uses the engine temperature to decide if compressor should engage. if it is defective and looking
like -40 to BCM it will disable AC. BCM then passes this temp data onto the ECM for motor warmup function. Replace the engine temp sender and the connector on it as it is probably intermittent.
Also check your 5V reference voltage to TPS as same voltage is used by the Temp sender circuit. any shorts to ground on wire harness?
You can then go into BCM diagnostics and look at the engine coolant temp display and see if it is correct reading. before start motor does the temp display ambient.
 

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Registered
1992 Cadillac Sedan DeVille 4.9L (Deceased), 1991 Cadillac Sedan DeVille 4.9L
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103 Posts
Discussion Starter #12
Haha, thanks for the science lesson Ranger! After 2 years of college Physics, I should probably know better.

Anyway, the connector the ground goes into ended up being the culprit. I ended up cutting the connector out and using wire nuts; So far, so good! I'm not sure why it lost connection more when it was hot, but I'm sure there's a science lesson somewhere to explain it :p

That's the first half of the battle won. Now, I have to figure out why the Electronic Climate Control display takes so long to turn on. The longer I go without driving my car, the longer it takes to turn on (About 5 minutes at most). Sometimes the buttons are functional when the displays not on, but mostly it just defaults to 75 degrees with the defroster on and you have to wait. My old Climate Control unit used to do this until eventually it got worse and worse and then didn't work at all. Do you think this is a problem with the wiring in my car, or is it a coincidence and it's a problem with the controller itself? This is less of a problem, but probably a more difficult one to figure out.

Thanks for all the help up until now!
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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86,793 Posts
Just a WAG on my part, but it kind of sounds like the display unit is getting old and tired.
 
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