MrEldo97 Posted June 30, 2008 Report Share Posted June 30, 2008 Does anyone know if the A/C system in a Northstar Cadillac must be evacuated prior to changing out the A/C Low Pressure Switch? I think mine needs to be changed, car is a '97 Eldorado. Thanks Quote Link to comment Share on other sites More sharing options...
KHE Posted June 30, 2008 Report Share Posted June 30, 2008 I would need to double check the service manual but I think the pressure switches have schrader valves in the lines so the refrigerant would not need to be recovered. The high and low side temp. sensors do not and the refrigerant must be recovered prior to replacement. Out of curiousity, why to you think the pressure switch needs to be replaced? Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
MrEldo97 Posted June 30, 2008 Author Report Share Posted June 30, 2008 I'm getting a A/C compressor off, low refrigerant message on the computer and I have power at the switch, relay and compressor. I made a quick and dirty check last night - the compressor runs fine and the system cools when I jump the relay- I have power at the switch connector, at the relay and at the compressor. I haven't jumped the switch yet, I'm going to do that tonight. Quote Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 30, 2008 Report Share Posted June 30, 2008 I believe Kevin is correct you can remove the low pressure switch without evacuating the system, there is a valve in there, I needed to replace mine after I replaced my compressor. Quote 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 Link to comment Share on other sites More sharing options...
MrEldo97 Posted June 30, 2008 Author Report Share Posted June 30, 2008 Thanks, I'm going to pick one up at Autozone on my way home from work and install it tonight. Quote Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 30, 2008 Report Share Posted June 30, 2008 Thanks, I'm going to pick one up at Autozone on my way home from work and install it tonight. It should solve your problem, I was getting a false low pressure reading also, it was the sensor. I jumped it for a couple of days, KNOWING that the system was fully charged. Quote 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 Link to comment Share on other sites More sharing options...
KHE Posted June 30, 2008 Report Share Posted June 30, 2008 Mr. Eldo, How do you know that you do not have a leak? I would have the system leak checked prior to throwing parts at it. The pressure sensor rarely causes a problem. Sometimes the high side or low side thermisters will go bad but those failures are rare (unless someone installs the orifice tube in the wrong direction - that will destroy the low side thermister.). Check the compressor body for oily/greasy residue - that may indicate the compressor case o-rings are leaking. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
BodybyFisher Posted June 30, 2008 Report Share Posted June 30, 2008 (unless someone installs the orifice tube in the wrong direction - that will destroy the low side thermister.). Guilty as charged (no pun intended)..... Quote 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 Link to comment Share on other sites More sharing options...
KHE Posted July 1, 2008 Report Share Posted July 1, 2008 To add: The low refrigerant code is determined by the high/low side thermistors (temperature sensors), not the pressure switch. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
MrEldo97 Posted July 1, 2008 Author Report Share Posted July 1, 2008 (edited) Hooked up a set of guages (friend has), the guages checked out fine and the car cools as it should. If this doesn't work then off to the shop for diagnosis and (I hope) repair. Edited July 1, 2008 by MrEldo97 Quote Link to comment Share on other sites More sharing options...
KHE Posted July 1, 2008 Report Share Posted July 1, 2008 When you say the gages checked out - I assume the pressures met the requirements in the shop manual for ambient air temp and relative humidity right? If so it is possible the pressure switch is bad. Make sure to change the o-ring that is behind the pressure switch - if you don't, you will have a leak after you swap out the switch. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
MrEldo97 Posted July 1, 2008 Author Report Share Posted July 1, 2008 Thanks for the Heads Up about the O ring. The one thing I wanted to do (may do tonight) is jump the connector at the switch. I jumped the relay and the system works fine, so I assume the system will also work if I jump the switch... Quote Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 1, 2008 Report Share Posted July 1, 2008 I had mine jumped for a couple of days with a paper clip or copper wire Quote 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 Link to comment Share on other sites More sharing options...
MrEldo97 Posted July 1, 2008 Author Report Share Posted July 1, 2008 I had mine jumped for a couple of days with a paper clip or copper wire Paper clip - the best kind of switch there is... Quote Link to comment Share on other sites More sharing options...
KHE Posted July 2, 2008 Report Share Posted July 2, 2008 Thanks for the Heads Up about the O ring. The one thing I wanted to do (may do tonight) is jump the connector at the switch. I jumped the relay and the system works fine, so I assume the system will also work if I jump the switch... Be sure to lube the o-ring with 525 viscosity refrigerant oil prior to installation. Quote Kevin '93 Fleetwood Brougham '05 Deville '04 Deville 2013 Silverado Z71 Link to comment Share on other sites More sharing options...
Michael Suhrstedt Posted July 14, 2020 Report Share Posted July 14, 2020 97 cadillac eldorado how to bypass ac pressure sensors? And should you Quote Link to comment Share on other sites More sharing options...
rockfangd Posted July 15, 2020 Report Share Posted July 15, 2020 You should not. One is a low cutoff that protects the compressor. The other is a high cutoff that protects everything if pressure gets too high. For testing you could unplug and jumper the plug, but for normal use I do not recommend it. Welcome to CaddyInfo Quote GM FAN FOREVER Nice, clean, luxury= fine automobile Link to comment Share on other sites More sharing options...
BodybyFisher Posted July 15, 2020 Report Share Posted July 15, 2020 7 hours ago, Michael Suhrstedt said: 97 cadillac eldorado how to bypass ac pressure sensors? And should you I agree with @rockfangd but explain what you are trying to do in more detail for us, thanks I have ONLY jumped my 96 for diagnostic reasons, and then purchased a new pressure switch Quote 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 Link to comment Share on other sites More sharing options...
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