No Power to AC Compressor

[K3500crewcab]

UPDATE:
I bypassed the relay today with the help of a friend from work and the compressor immediately kicked on. We then swapped the relay with a new one I already had on hand and it had no effect, so the bypass wire is currently still attached on one end to the power box in the engine bay (the wire is removed for now to keep the battery from draining).

Could it cause any issues to run the truck like this until I figure out where the rest of my electrical issue is at, as long as I'm not pushing it or going high RPM? I live about 5 minutes from work and will only be on small and backroads.

We have a plan to hook a meter up and test a few other things, but it was not clear to me exactly what he was planning on checking and he does not have the proper meter with him today. I will keep this updated until we get it resolved. Thanks for you guys' help so far.

Hey 251TwoDoor,
I am experiencing the same issue with my 98. Jumper wire at the A/C relay will engage the compressor clutch but when I put in a brand new relay I get nothing. I’m hoping your still on this page since 2016 was when this was posted, just trying to see if you ever figured it out or if anyone else has solved this problem

 

[PlayingWithTBI]

I’m hoping your still on this page since 2016 was when this was posted

Yeah, if you click on his avatar, it'll show you when he was last seen. In this case, over a year and 1/2.

 

[Mech_Lyfe]

Hey 251TwoDoor,
I am experiencing the same issue with my 98. Jumper wire at the A/C relay will engage the compressor clutch but when I put in a brand new relay I get nothing. I’m hoping your still on this page since 2016 was when this was posted, just trying to see if you ever figured it out or if anyone else has solved this problem

I take it you have a 98 Tahoe?
here is a quick checklist and I’m sure you have done a few and some have been listed in this thread already.
check system is charged
Check all fuses and relays (both eng bag and under dash)
You can jump the pressure switches one at a time until you find the one that is bad, at the same time you can make sure that it has power at the switch.
Check to make sure the head unit is sending the signal
Let me know if you need more help.

 

[east302]

It looks like the VCM provides the ground for the relay, so if it isn’t grounding then there’s a switch upstream that is preventing it due to a defect or charge issue. Or, as above, the panel isn’t sending the signal.

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[K3500crewcab]

Yeah, if you click on his avatar, it'll show you when he was last seen. In this case, over a year and 1/2.

Thank you

 

[Zerio29]

UPDATE:
I bypassed the relay today with the help of a friend from work and the compressor immediately kicked on. We then swapped the relay with a new one I already had on hand and it had no effect, so the bypass wire is currently still attached on one end to the power box in the engine bay (the wire is removed for now to keep the battery from draining).

Could it cause any issues to run the truck like this until I figure out where the rest of my electrical issue is at, as long as I'm not pushing it or going high RPM? I live about 5 minutes from work and will only be on small and backroads.

We have a plan to hook a meter up and test a few other things, but it was not clear to me exactly what he was planning on checking and he does not have the proper meter with him today. I will keep this updated until we get it resolved. Thanks for you guys' help so far.

With the pin jumped, does the A/C work well? If it's not blowing really cold, odds are you have low pressure in your system and the relay won't kick in for risk of damaging the compressor. If it is blowing cold, then you probably have either an electrical issue or a bad pressure switch. Without knowing the pressure in the system, I wouldn't run it with the pins jumped. It could harm the compressor prematurely, and if the compressor grenades, it can take out other A/C components.

 

[Bret Miller]

My 96 k1500 had the same problem . If I jumped pin 30 with pin 87 where the relay is under the hood it would make the clutch engage. Ended up being the Ecm was bad . That's what gives the relay its ground when you turn on the ac button. Replaced the Ecm and now it works.

 

[HotrodZ06]

Might could check live data with a scan tool to see if the pcm is getting the a/c request.

 

[tonytruck]

hi i have a 1989 2500 and when it warms up driving down the highway my ecm/ing fuse keeps blowing dose anyone have answers thanks

 

[1998_K1500_Sub]

hi i have a 1989 2500 and when it warms up driving down the highway my ecm/ing fuse keeps blowing dose anyone have answers thanks

You might want to start a new thread for this problem.

Please describe the symptoms in more detail, if possible, including events before and after the fuse blows.

What's the engine / trans combo?

What other problems are present, if any?

Have there been any electrical repairs / modifications / changes made to the vehicle, to your knowledge?

If your truck has a lockup torque converter, has it been functioning correctly, i.e., you plainly notice the locking and unlocking of the torque converter when it happens?

The 1989 service manuals contain schematics and are available for download as .pdf files, here:

88-98 Service Manuals

Over the years I have collected a bunch of GM service literature. Links to PDF Scans of service and STG manuals and a links to the Parts manuals. You'll need the FREE Adobe Acrobat reader to open these files. Get it directly from Adobe here {http://get.adobe.com/reader/} If you're not...

www.gmt400.com

and here too IIRC:

GMT400 CK Service Manual Project

GMT400 CK Manual Project - The 1947 - Present Chevrolet & GMC Truck Message Board Network

GMT400 CK Manual Project The 1988 - 1998 GMT400 Chevy & GMC Pickups Message Board

67-72chevytrucks.com

Confirm: Is this the fuse that keeps blowing, the "ECM IGN" fuse shown on the LH middle of this figure?

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(figure from pg. 18 of ST-375-89-EDD_1989_T400_CK10-30_Chevrolet_Wiring_Manual.pdf)

You said the fuse blows when the engine gets warm. Well... It appears that ECM IGN circuit, among other things, supplies power to the torque converter clutch circuit (pg. 43 and 82 of the wiring manual). Coincidentally, the torque converter clutch will remain disengaged while the engine's cold, but is enabled when the engine is warm. That's when you say the fuse blows.

Let me look into this.

Meanwhile, please respond to the questions I posed.