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Charging A/C bypass relay?


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98-Deville

My compressor stays on for 10 seconds them cuts off, I want to replace my low pressure temp sensor and pressure sensor; all low and high pressures are good. I found that the Low Pressure sensor maybe the issue and I will need to remove the R-134 vac and refill at 2-Lbs. I read some where that I could bypass the compressor relay to enable the compressor to fill. Is this the best way if so where is it located, I belive its in the trunk but cannot find a daigram on which relay is what.

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When you delete the low pressure code from the PCM, the compressor will restart long enough for you to charge the system. Have you deleted the code? My experience is that by deleting the code you get sufficient time to start charging the system after an evacuation.

If it is only staying on for 10 seconds after you delete the code, try jumping the connector on the low pressure sensor to 'fool' the PCM, but DO NOT leave it jumped, and make sure you have the proper freon charge

Have you checked to see if you have a DTC code set for low pressure? Low pressure will set a code. If the sensor is bad (I had a bad sensor), you can jump it to verify that fact, as the code will no longer set after 10 seconds, but DO NOT leave the sensor jumped as you will ruin your compressor

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Why are you replacing the low side temperature sensor??? How have you determined that it is defective? If there not any codes stored that relate to the low side temperature circuit, you are wasting your time and money.

If the issue is the compressor shuts down and the ACM disables the compressor, you should have a low refrigerant code set. If that is the case, perform a leak check, repair the leak and then have the system evacuated and recharged.

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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As I mentioned the pressure on both Low and High are with in specs. Reading on line it was mentioned that the low pressure temp sensor can go bad causing this issue. It thinks the temp is too low and shuts it off while not throwing a code. When I removed the low pressure temp switch connector the low charge warning came on, I cleared it. I have asked these same questions in the past and keep getting; its low check for leaks Etc. This is not the problem it must be a sensor issue that is not bad enough to pull a code.

If anyone has actual advice as to how to check mointor or otherwise look at the reading live please chime in. I have a scope, meter and all the tools, the manual says to do the Dia Tool, I purchased a new modual for my Snap-On brick but it lacked the A/ c portion. So at this point its the dealer or more trouble shooting.

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As I mentioned the pressure on both Low and High are with in specs. Reading on line it was mentioned that the low pressure temp sensor can go bad causing this issue. It thinks the temp is too low and shuts it off while not throwing a code. When I removed the low pressure temp switch connector the low charge warning came on, I cleared it. I have asked these same questions in the past and keep getting; its low check for leaks Etc. This is not the problem it must be a sensor issue that is not bad enough to pull a code.

If anyone has actual advice as to how to check mointor or otherwise look at the reading live please chime in. I have a scope, meter and all the tools, the manual says to do the Dia Tool, I purchased a new modual for my Snap-On brick but it lacked the A/ c portion. So at this point its the dealer or more trouble shooting.

Based on the bolded statement, your low pressure sensor is good

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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Well if you are correct them what is going on with this system? Do you know what the ohm value range is for the low pressure temp switch, maybe I can place a resistor across the connector to check its operation.

That is a switch, its either ON or OFF

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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The low side temperature sensor is a thermister - there should be a resistance table in the shop manual.

Is the compressor clutch air gap within specification?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The low side temperature sensor is a thermister - there should be a resistance table in the shop manual.

Is the compressor clutch air gap within specification?

OPPS, my mistake, I am thinking low pressure switch, thats along the passenger side wheel well

Pre-1995 - DTC codes OBD1  >>

1996 and newer - DTC codes OBD2 >> https://www.obd-codes.com/trouble_codes/gm/obd_codes.htm

How to check for codes Caddyinfo How To Technical Archive >> http://www.caddyinfo.com/wordpress/cadillac-how-to-faq/

Cadillac History & Specifications Year by Year  http://www.motorera.com/cadillac/index.htm

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I read this is a termsistor that changes value with temp is this correct?

So let me get back to basics, my pressures go up then compressor shuts off is this normal. Should the pressure readings stay somewhat stable? I had this charged a while ago and put a gauge on it and although they looked in spec it does not stay on after the compressor kicks off. I can start over with a Vac and 2-Lb's of R-134 but cannot remember if the pressure should change like that. Is there a cut off point on the high side 220 and it seems to shut off.

Thanks

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If the compressor is shutting down without setting a DTC, it is likely NOT due to the PCM commanding the shutdown. Rather, some other evil is afoot. I'm left wondering about the clutch itself or its associated wiring including its electrical connector and ground. If 12 volts is present on the clutch when it disengages it would indicate a clutch failure, poor ground or the clutch air gap KHE mentioned in post #8.

The troubleshooting chart is attached.

Regards,

Warren

98Deville_AC.doc

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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I bypassed the relay and compressor runs but pressure was down to 20/150 I added a little R-134 and pressure is up to about 36/175 with relay in. With relay bypassed it is went to 14/160 I did not want it to go any lower, anyone know the cut off pressures for this car? With relay back in it still cuts off it's 90 Degress and humid where should I be at my records indacate 36-48 185-235

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. . . anyone know the cut off pressures for this car?

See the attached document.

98Deville_Sensors.doc

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There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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It seems I may have a blockage I guess I need to remove and check the orifice tube tube for any crap. From what you sent me seems like the Hi/Low switches are not the issue due to the pressures I am seeing. Since I can bypass the relay and compressor stays on but drops low 14/160 but not when the relay is installed that is strange. Could it be that the R-134 is that low, when the relay is in it cycles at 36/175 I must be missing something!

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It seems I may have a blockage I guess I need to remove and check the orifice tube tube for any crap. From what you sent me seems like the Hi/Low switches are not the issue due to the pressures I am seeing. Since I can bypass the relay and compressor stays on but drops low 14/160 but not when the relay is installed that is strange. Could it be that the R-134 is that low, when the relay is in it cycles at 36/175 I must be missing something!

With a blockage I would expect the 160 part of your 14/160 to rise, but obviously it hasn't. On the other hand 14/160 seems entirely consistent with an insufficient charge.

Are you sure you put 2 lbs. in there?

I just assumed you inspected/changed the orifice tube.

I don't understand why you don't have a DTC set if the programmer is commanding the clutch off.

Regards,

Warren

Posted Image

There is no means of avoiding the final collapse of a boom brought about by credit expansion. The alternative is only whether the crisis should come sooner as the result of a voluntary abandonment of further credit expansion, or later as a final and total catastrophe of the currency system involved. - Ludwig von Mises

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I have my friend and his crew using my lift so I intend to get a OT cost $2.49 vac it down and fill it with 2 Lbs then go from there.

Thanks for your feedback I'll keep you posted! It is odd the low indactator does not come on I agree but it went only to 14 so it may be on the edge.

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It is possible the contacts on the A/C compressor relay are not making continuous contact and that is kicking out the compressor. Maybe try swapping the A/C relay with another relay and see what happens?

Kevin
'93 Fleetwood Brougham
'05 Deville
'04 Deville
2013 Silverado Z71

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The Filter is blocked, I removed the old filter and will vac it down then replace with the new filter vac it again and charge.

The blockage is not severe but the first filter portion has a lot of crap in it including some metal shavings. I had A/C shop replace the Compressor, Condensor amd R/D a few years ago. The air was good for a while then started to go down hill slowly, I assume this was due to the previous repair and not flushing it out completely.

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When the compressor starts throwing debris through the system, you need to change the compressor, accumulator and the condenser (it can't be properly flushed)and THEN flush all the lines. If you don't, another compressor failure is in the offings and that appears to be what's happening here. Either debris was left in the system or the compressor is failing because debris was left in the system. Maybe you'll get lucky and the orifice tube screen caught it all and the compressor is still good. Change the orifice tube and see if that helps, but if you have problems again, you'll know right where to look.

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I replaced my blower motor that went bad after 4-months and got that working first. I replaced the tube and vacuumed it down with tube removed, filled with R-134 to clean, added tube and Vacuumed again the sealed everything up. The one thing I found you cannot bypass the relay to charge with that done the pressure went up to 39/350 so I stopped. Once I replaced the relay I was able to fully fill it and at 97 Degrees 90% humidity pressue went to 49/270 and air was around 75 Degrees.

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What do you mean by "filled with R-134 to clean"? If you mean that you cleaned the lines that way, that won't do it. You need a flush gun and solvent.

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Not cooling enough I have done the following:

Vac system, recharge at 2Lb's and new orifice tube.

98 Degrees Hi Hum

At Idle temp will go to 70

At drive goes to around 80

I checked the pressures:

53/295 @ idle

40/350 at 1500 Rpms then compressor kicks off.

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