GM Truck Club Forum banner
1 - 20 of 27 Posts

·
Registered
Joined
·
8 Posts
Discussion Starter · #1 ·
I’m new to this page.. and I just bought a 97 GMC Sierra 2500 v8 and I bought it for 3700 and I feel like I may have gotten ahead of myself.. but I couldn’t resist. There’s a couple things wrong and one Ill just off with is the electric confusion my ac clutch stays engaged unless I unplug it from under hood it hardly blows from my vents but it’s cold just barley bows the guy who sold it to me says he replaced the ac thing under hood circled in pic but I’m not sure what’s wrong or if the second pic has any thing to do with it but I just need some help my Indash control doesn’t change anything either and also the line circle in pics freezes instantly when ac is plugged in
Circuit component Hardware programmer Computer hardware Electrical wiring Gas
Motor vehicle Automotive fuel system Handwriting Automotive air manifold Automotive tire
Motor vehicle Automotive tire Automotive lighting Hood Automotive design
 

·
Registered
Joined
·
16,191 Posts
Find the AC relay in the under hood fuse panel and pull it out, see if the compressor clutch releases.
 

·
Registered
Joined
·
16,191 Posts
No, just remove the relay.
Does the AC stop?
 

·
Registered
Joined
·
16,191 Posts
Ok, I don't see the wire in your picture.
Is it factory, or is it just pushed into one of the relay slots?
 

·
Registered
Joined
·
3,979 Posts
ya Ray theres a jumper. it's kinda hard to see especially on a phone, the wire has no insulation. it's right where the ac relay is supposed to be.

heres my 98 C1500 Sierras fuse boxes. they should be almost the same.

Al

Gas Technology Font Machine Food

Circuit component Passive circuit component Hardware programmer Computer hardware Gas
 

·
Registered
Joined
·
3,979 Posts
So I dont know anything about the AC system but someone, for some reason has jumped the pins where the ac relay is supposed to be and that is why it is running all the time. you need to replace this jumper with a new relay. since I dont know anything about AC I dont know why someone would jump the relay except for testing. the AC turned on for whatever reasons and that wont happen unless the relay is replaced.

Al
 

·
Registered
Joined
·
3,979 Posts
Also the dash fuse panel has pin 21 (on my truck its a 10A Security/STRG? I'm not sure what STRG might stand for)

and Pin 24 (which on my truck is 20A and 4WD according to my label, well WTF this is a rear wheel drive truck so I dunno what it actually does.)

the wiring on these trucks can all be slightly different and 2 identical trucks may be slightly different. I have a 97 Burb as well.....

Al
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #12 ·
Ok so I tried trading the relay with one of the other relays but still nothing it only engages with the jump pin. Should that line freeze instantly? I posted that pic also ..Sorry I know nothing about vehicles except I love chevys and I would like think my mind is “mechanicaly enclined” lol but I am not. I’ll post the pic again..
Audio equipment Eyewear Font Electronic component Electronic engineering
Motor vehicle Automotive tire Automotive lighting Hood Automotive design
Audio equipment Eyewear Font Electronic component Electronic engineering
Motor vehicle Automotive tire Automotive lighting Hood Automotive design
 

·
Registered
Joined
·
3,979 Posts
I dont know AC at all but to understand what turns the compressor on I would need to see a schematic. defrost and obviously turning the AC on will activate the compressor but I have no idea what or how it reacts.
 

·
Registered
Joined
·
16,191 Posts
Ok guys I see that jumper, let me go back and reread the last few posts, is that a relay socket, or a couple of fuse sockets?
 

·
Registered
Joined
·
16,191 Posts
I dont know AC at all but to understand what turns the compressor on I would need to see a schematic. defrost and obviously turning the AC on will activate the compressor but I have no idea what or how it reacts.
Al, it's a simple system until you add all of the safety checks.
Here's the simple part.
At the compressor, there is a clutch between the compressor shaft and the pulley being turned by the belt.
This clutch is 2 metal disks, when the disks are pulled together the compressor operates.
There is an electro-magnet in the clutch that operates it.
12 volts is needed at this magnet, it usually is provided when the AC clutch relay operates.

Edit:
Sorry, I hit the post button.
The AC clutch relay operates when AC, or defrost is selected.
 

·
Registered
Joined
·
3,979 Posts
I have worked with relays a few times wiring them up but I have no idea what these pins that are jumped do. my guess is power in and the other is power on. but that is just a guess.

Motor vehicle Automotive tire Automotive exterior Hood Rim
 

·
Registered
Joined
·
8 Posts
Discussion Starter · #18 ·
Ok guys I see that jumper, let me go back and reread the last few posts, is that a relay socket, or a couple of fuse sockets?
Yes.relay the relay was in it but I took it out like you said to try and the jumper was under it…?
 

·
Registered
Joined
·
16,191 Posts
Ok Al, thanks.
@Gretasimanek , you pulled the relay and the clutch didn't release; it didn't release until you removed the jumper, is this correct.
If so, there is something wrong with the relay circuit.
Remove the jumper, it's just borrowing 12 volts from the starter circuit.
Test the AC relay by putting it in the starter socket, and start the truck, if it starts normally, the relay is good
Put the AC relay back in its socket and look for the AC relay fuse.
I'm guessing the fuse is blown, it should be close to the relay.
 

·
Registered
Joined
·
16,191 Posts
Al, you were posting while I was typing.
I would say one end of the jumper was in the AC clutch magnet lead and the other is the starter relay 12 volts.
 
1 - 20 of 27 Posts
Top