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Dangers of bypassing AC compressor Relay


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nickexists
New User

Feb 8, 2016, 10:43 AM

Post #1 of 5 (2400 views)
Dangers of bypassing AC compressor Relay Sign In

I was helping my friend to troubleshoot non-functioning AC in her 2008 Volvo S60. I determined that the AC relay is functional but for whatever reason the computer isn't ever sending the signal to activate the compressor (the signal going to the relay holds at a steady 9.5V regardless of the AC setting). By replacing the relay with a jumper I was able to show that the AC system does in fact work. A mechanic had previously determined that there was no problem with the refrigerant levels and that the problem was electrical, but the engine compartment appears to be too compact for me to access the pressure switches.

My friend can't really afford to have the car properly fixed right now and it gets very hot here in the summer and so she wants to just manually jump the relay whenever she wants the AC on. This may work in the short term but I worry that forcing the Compressor to stay on regardless of sensor inputs could cause serious damage. I wanted to see if anyone more knowledgeable than me could provide insight into what the risks of this approach are and how valid my concerns are. Thanks.


kev2
Veteran
kev2 profile image

Feb 8, 2016, 11:19 AM

Post #2 of 5 (2397 views)
Re: Dangers of bypassing AC compressor Relay Sign In

STOP .....do not bypass rig or otherwise redesign the AC system. Doing more harm than good. risking the compressor failing and that is $$$ big expense compared to repairing the issue.
I do not know your location Be advised here in the USA* you will need a licensee to work on automotive AC systems. EPA 609 certified.
repair the reason for the PCM denying the AC request - likely there are codes, may not turn on the ck eng light- a set of AC gauges both high and low are suggested as well as a scanner.


*otherrr locations are draconian - be warned


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 8, 2016, 12:28 PM

Post #3 of 5 (2388 views)
Re: Dangers of bypassing AC compressor Relay Sign In

I second that.

DO NOT jump out any relays. The computer is not turning it on for a reason and ignoring that can cause BIG problems.



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nickexists
New User

Feb 8, 2016, 1:06 PM

Post #4 of 5 (2382 views)
Re: Dangers of bypassing AC compressor Relay Sign In

Thanks for the feedback guys. I'll pass that along to her. Would you happen to know about how much getting an electrical issue like this would cost? Also, just for my own understanding and curiosity could you give any specifics on what might go wrong in bypassing the relay like this?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 8, 2016, 1:11 PM

Post #5 of 5 (2381 views)
Re: Dangers of bypassing AC compressor Relay Sign In

Third: Nickexists - you could make up part of what could go wrong for this but miss what was intended. It shut down for a reason and not convinced you know what yet.
Assorted shut downs will be pressure too low of returning gas to compressor to prevent lock up. Simple enough but it also knew how warm/hot the temp was when it was low or should have on this type car.
Compressor will also shut down on some if you are asking for full engine power = WOT and if that has failed never kick on. List goes on, maybe if engine is too hot, fans not working properly, high pressure too high.
It was designed to be the best it could be when working properly without damage you risk by rigging up something.
Fix it properly, get codes already suggested it might not be as nasty as you might think?


T







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