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97 SLS & 06 STS-4 Cadillac
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62 Posts
Discussion Starter #1
The compressor will not stay on. I got 69 deg temps when driving and 60 when stopped, something is telling the compressor to turn on/off too much;.

New compressor,and charge, all low/hi PSI are good.

If i jump the regulator i get 55 degree air.

What do i do, the service manual is not helping me with this as i tried to follow it..

I'm about ready to install a switch to the A/C clutch to go manual but this is not a fix, I know.

All the fan system seem normal as they are trying to cool the car down.

As I said if i jump the AC compressor relay everything seems to work normal..

HELP.

NO codes listed but a PCM 1611

Shawn
 

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97 SLS & 06 STS-4 Cadillac
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62 Posts
Discussion Starter #4
Re: 97 cadillac SLS air conditioning HELP

low PSI switch is good. if i bypass it, compressor still turns on (45sec) then off. Then back on(45 sec) then off etc.

I replaced the compresor thinking that was the problem, gauge readings were slightly off but now I know it was a knee jurk fix. (try to fix)
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: 97 cadillac SLS air conditioning HELP

A short cycling compressor (maybe 10 seconds ON, 10 OFF) is usually an indicator of a slightly low Freon charge. 45 seconds ON/OFF sounds more like a cabin air temperature sensor/control problem.

Anybody know if a 97 has that tiny fan and sensor inside the left dash panel ???

Nitro, Does your car have a little 1" square grille in the dash, just left or right of the steering column ???
 

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97 SLS & 06 STS-4 Cadillac
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Discussion Starter #6
Re: 97 cadillac SLS air conditioning HELP

No grille that I can see.

I Just installed the compressor pulled vacuum, recharged (2lbs) and tested. 40-45 PSI low 240-250 high.

Thing is if I jump the compressor to make it run continuously the car cools to 55F discharge air and runs as normal. Meaning the fan goes high then cuts back at normal speed and everything seems to work as designed.

Defiantly seems like something is shutting the compressor down because it thinks reached its set point. (but it didn’t)

Now, Things that I don’t understand:
Why? When driving the discharged air temp is at 70F, as soon as you stop the temp goes to 60F and stays there. Then once you start driving again the temp immediately goes back to 70F discharge temp and stays there. Stop and it will return to 60F

For the life of me I cant figure that out but it seems to be temp related. Could it be the air is superheated in the condenser at a stop due to air flow and that makes the system more efficient is why it decreases discharge temp? don’t know but that one more bit of info I can tell you.

One other thought?
Could it be the thermistors thinking it’s to cold and going to frost the system, hence the shutdown??

Thanks guys im really lost with this one
 

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1997 Seville STS, 2000 Seville STS
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1,694 Posts
Re: 97 cadillac SLS air conditioning HELP

97's have a small grille above and to the right of the instrument cluster, tucked under the dash overhang, thats where your cabin air is drawn into the sensor.

Have you adjusted the amount of refrigerant in the system (added any)? Could be that theres too much in there now and you've flooded the evaporator (full of liquid freon instead of gaseous). Don't even know if this applies to orifice tube systems anymore, but it does with the old style temperature control valve systems and it will keep the system from cooling properly.
 

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2010 DTS
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Re: 97 cadillac SLS air conditioning HELP

40-45 PSI low 240-250 high.
Just off the top of my head, those pressures seem a little high. The compressor is supposed to cycle.

When driving the discharged air temp is at 70F, as soon as you stop the temp goes to 60F and stays there. Then once you start driving again the temp immediately goes back to 70F discharge temp and stays there. Stop and it will return to 60F
I don't understand this either. The other way around would make more sense. Did you remove the fans? Any chance you installed them backwards?
 

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1997 SLS
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550 Posts
Re: 97 cadillac SLS air conditioning HELP

Mark is right...there is a tiny opening to the right of the main cluster tucked under the dash to check cabin temp, you should gently vacuum it to be sure it's not clogged with dust. Generally, if you check the aluminum tubing as it goes into the evaporator just past the orifice tube junction, is it cold and "sweating"? This is a simple test to see if your evaporator is properly chilling. What about malfunctioning air mix doors? You might not get a code - you have checked all of your ACMs for any Current or History, correct? Sometimes the linkage to the air mix doors can get out of adjustment sending in undesired heat at the wrong time.
 

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97 SLS & 06 STS-4 Cadillac
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Discussion Starter #10
Re: 97 cadillac SLS air conditioning HELP

I never touched the fans, they work when the compressor is on per the service manual.

System was drained of Freon and refilled at compressor/ accumulator /orifice tube change. 2lbs per the manual

If any inside temp sensor were bad than How come it all works (cools) when i jumper and continuously run the compressor?

Yes I understand the compresses should cycle (CVCOT?) or something along that name is what Cadillac calls it. Issue is though that my compressor does not run long enough between cycles.
Shawn
 

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97 SLS & 06 STS-4 Cadillac
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Discussion Starter #11
Re: 97 cadillac SLS air conditioning HELP

I’ll check the dash as I know of what you’re talking about.

Question?? The 2 thermisters on either side of the orifice tube… Could it be than one of those are bad and telling the computer that the evaporator is freezing, hence the compressor disengagement..

What do those 2 temperate sensors do and how?
 

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1997 SLS
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550 Posts
Re: 97 cadillac SLS air conditioning HELP

I don't think the compressor cycling is a function of the inside temp settings (I could be wrong!). The inside temps are varied by the CC settings. Oddly, the compressor (unless bitterly cold outside) and heater core are always "on" per se. The comfort level in the cabin is an automatic adjustment of the air mix doors behind your glove box. Unless you or the past owner did maintenance on them, they could be out-of-adjustment causing warm air to enter the system. Check the aluminum tube just past the orifice junction to see if it is cold. If not, then you do have a freon/charge issue. BTW, when you changed your compressor, it did have the tabs on it with an oil charge, correct? I also assume you checked your orifice tube screen and there was no debris in it before you evacuated and recharged?
 

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2005 STS4 1SG: GM Acc Lights, Corsa, Platnium Grille, Volant
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15,987 Posts
Re: 97 cadillac SLS air conditioning HELP

Schedar valve?
i think thats what its called?
maybe that?
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: 97 cadillac SLS air conditioning HELP

The Schrader valves in the piping are the service and pressure ports. Nothing to do with temp control.
 

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2010 DTS
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87,575 Posts
Re: 97 cadillac SLS air conditioning HELP

I do not believe that the cabin temperature sensor has anything to do with this problem. It definitely has nothing to do with when the compressor cycles on or off.

The two thermistors you speak of are the high side temp sensor and the low side sensor. If either was bad it would set a DTC.

There is no schreader valve in the '97 A/C system.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Re: 97 cadillac SLS air conditioning HELP

How do you evacuate/charge the 97 system ? You sure can't hook a gauge set and/or freon bottle up to an open system..........

There's a picture of an engine, pre-2000, in here somewhere showing two service ports, one high side and one low side (different fitting sizes so you don't charge to the high side), and those puppies are controlled by Schrader valves, exactly the same principle as your tire valves.

Take the black plastic caps off the service ports and look at the little relief tit in the center of the port. That's the Schrader valve. The inside of the service port is also threaded so the valve can be replaced instead of the entire pipe.
 

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2010 DTS
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87,575 Posts
Re: 97 cadillac SLS air conditioning HELP

The R134a systems don't have "Schreader" valves (R12's did). They have a different type of quick disconnect fitting like an air compressor, not a tire valve. That's all I was trying to say.

Short cycling points to the system low on refrigerant as you mentioned earlier. I still think the system is low. Are both the inlet and outlet pipes to the evaporator cold, sweating and within a degree or two of each other?
 

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97 SLS & 06 STS-4 Cadillac
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Discussion Starter #18
Re: 97 cadillac SLS air conditioning HELP

Hey guys. Again i jumped the compressor relay (so it would run non stop)


Drove the car around and everything works perfect, output air temps as low as 52F. When the temp reached my 70 set point the fan kicked down to normal and even super quite mode. Soo, this proves my mechanical system,compressor/charge/air doors and fan controls are working as they should.

The key here is when i unjumper the compressor relay i get 40 sec on, 10 secs off 40sec on 10 secs off etc over and over.

Its got to do with something wanting to trip the compressor off. And due to that i get limited cooling.

I get No Codes....

What could it be?
 

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1997 SLS
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550 Posts
Re: 97 cadillac SLS air conditioning HELP

I'll have to go out and time my cycles as my system is OK for now (Phoenix heat!). There is a danger in continuous operation of the compressor - there is a built-in rev limiter...I think it cuts out over 2500 rpm. If you defeat that, you could damage the compressor.
 

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97 SLS & 06 STS-4 Cadillac
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Discussion Starter #20
Re: 97 cadillac SLS air conditioning HELP

Yes that would really help its 88-90 here in South Carolina and killling me!

Shawn
 
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