98 ac compressor issue

[dukcaln]

so my son comes home today and tells me his AC is blowing warm. I drove the truck two weeks ago and the AC blew cool. I went out and turned the truck on and turned the AC on and the compressor is not activating. I checked the fuses and they all looked good. (could the relay be bad) I was thinking it might be the low pressure switch maybe? Is it possible to be low on a charge? Do these system shut the compressor down if it needs charged? any ideas please?

[truckdude239]

The system does shut down due to low charge it does this to protect the compressor
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[dukcaln]

thank you, I seem to remember that the compressor was turn on and off a few weeks ago when I was checking the fluids. I believe that's a symptom of low charge as well.

I went and bought some A/C PRO and we will see if that works. Seems easy enough to use

[jerrymp]

Post back please with your success of the A/C PRO

[dukcaln]

so I put the AC PRO on the truck low side and the gauge went to the red which per the AC PRO instruction to add a half can until the compressor activates. I was not too crazy about doing that so I jumped the compressor with a paper clip at the low pressure switch and the compressor came on. So I then looked at the gauge and the reading was in the green approx. 35psi. I then checked the air and it was blowing cold, with the compressor jumped of course. So I am thinking it might be the AC relay or the low pressure switch?

What do you all think?

[dukcaln]

anybody find the low pressure switch for auto zone napa or orielly, I cant find it on the sites>

[dukcaln]

do you have to drain the system to replace the low pressure valve?

[country29]

http://www.oreillyauto.com/site/c/se...4WD&vi=1303614

hope the link works

[country29]

http://www.oreillyauto.com/site/c/se...Redirect=01957

here is the clutch cycle switch also

[dukcaln]

ok thanks, and so I am sure, where is the low pressure valve located (to connect the can too)? want to make sure its the right one. 1998 gmc 5.7

[dukcaln]

what is the difference between the clutch control switch and climate control switch?

[country29]

Originally Posted by dukcaln

ok thanks, and so I am sure, where is the low pressure valve located (to connect the can too)? want to make sure its the right one. 1998 gmc 5.7

if you have a can tap line, it will only connect to 1 of the ports, there is a low and high side port, it will only connect to the low side, it will be the smaller fitting.

[country29]

Originally Posted by dukcaln

what is the difference between the clutch control switch and climate control switch?

I'm not sure on this body style, but which ever 1 you jumped and it came on, if the Freon level is correct, is the 1 you need to change, normally the 1 over by the accumulator/drier is the low press switch, however it could be the 1 on the compressor on these, haven't gotten that far on mine yet! my 97 z71's engine is still in pieces in the garage! once I get it running I gotta figure out whats wrong with my a/c

[dukcaln]

the one on the accumulator is the one I jumped. It looks like the second one you posted, the clutch cycle switch. So do I need to bleed the system of all Freon or can I just unscrew and replace with no issues?

[country29]

it should be a Schrader valve style fitting, so you SHOULD be able to just take old 1 off and put new on, if not just be prepared to be quick with the new 1 in the other hand, ut it should have the Schrader valve in it and you shouldn't lose any Freon.

[country29]

if you change it and the compressor still doesn't come on, then it may still be low on Freon and without a set of gauges to verify your just gonna have to guess

[dukcaln]

ok thanks I will get the clutch cycle switch in the morning and replace. hoping that will do the trick since I can paper clip jump it and it will turn the compressor on and the unit will blow cold

[country29]

Wouldnt be the 1st time 1 of those switches went bad, again if you change it and it doesnt come on it may still need a little freon, but if its blowing cold while jumped its probably just the switch, good luck
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[dukcaln]

update, happy to say I replaced the clutch cycle switch on the accumulator and system works. Finished off the AC PRO can, which took about 20 min and it seemed to take it better with the can upside down instead of the side to side motion as per the instructions. AC PRO easy to use and the AC in the truck has never blown so cold. Country 29, thanks for all the feed back.

[country29]

No problem, anytime. Most cans do flow better upside down with a little rocking, just for future reference. Glad it worked out for you.
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