A/C Help....

[indasevens]

Where is the most likely place to look for a dead short somewhere in the wiring of the a/c???

What I have tried so far...
Jump a wire to blower motor..ran fine......
Jump a wire to a/c compressor ..engaged
Put fuse in fuse box and the moment I flipped up the switch on the panel it instantly blew the fuse.....I guess i need to just keep trying to eleminate things but thought one of you guys in here could point me in the most likely direction first!!!

Thanks

[bonnieclyde100]

from what you have said i would check the switch first .

[mrein3]

Originally Posted by indasevens

Where is the most likely place to look for a dead short somewhere in the wiring of the a/c???

What I have tried so far...
Jump a wire to blower motor..ran fine......
Jump a wire to a/c compressor ..engaged
Put fuse in fuse box and the moment I flipped up the switch on the panel it instantly blew the fuse.....I guess i need to just keep trying to eleminate things but thought one of you guys in here could point me in the most likely direction first!!!

Thanks

I put factory AC into a non-AC truck. Through that process (ordeal?) I learned more about factory AC wiring then I ever wanted.

Looking at used parts in junkyards I quickly discovered that most if not all the plastic connectors in the factory wiring harnesses were partially or fully melted. If you have the harness on the bench it is easy to rehab. Getting it on the bench may be a trick however.

Long story short I would look for melted wires at the connector at each junction. Going from memory there is the one behind the switch, one on top of the HVAC box under the glove box (that funky rocker switch deal that pushes the button when you slide the selector to AC), and one at the resistor block on the HVAC box.

One thing I can't remember is the high-speed circuit on these trucks. Lots of GMs of this vintage had a separate circuit for the high-speed fan setting. If you fan fuse blows on high-speed and not others you may just have an issue there. Look for a 10 or 12 gauge orange wire with an in-line fuse in the gutter along the firewall. Again I apologize for not remembering that particular on this wiring.

[indasevens]

Thanks everyone keep it coming....It is a factory a/c truck....I have the ""switch unit" out and looking at as much as i can to see the wiring but man just need to figure this out....I live in Florida!!!!

[Andy4639]

As stated the plastic connection on the switch itself will get hot and melt.
Mine was giving me a fit several years ago. It would work then quit. The terminals were getting hot and loose contact. Cool off and would work again. I finally took it all apart and redid all the connections with no problems.

[Andy4639]

These may help also.

[indasevens]

YES IT does.....Thanks alot.....Which switch should i check first??? Which one is more likely ====so far all wires look normal...still checking!!!

thanks again!!

[Andy4639]

1. Fan switch
2. Check the AC relay on the fire wall in 1 picture.
The switch itslf can go bad also. But make sure the plastic housing holding the wires is not burnt up and melted.

[mrein3]

Originally Posted by Andy4639

snip
But make sure the plastic housing holding the wires is not burnt up and melted.

That is what I'd look at first. After seeing so many bone yard harnesses with that plug melted, I have to believe it is a common problem.

If you look at that plug and its melted, I would buy a new switch, a new plastic plug, then re-do the wires there. To do that you'll need to go to NAPA and order a half dozen or so of part number 725147. This is the brass colored plug insert that makes the connection with the switch. I keep a bin full of these things because with 3 GMs of this vintage of laying around my yard I seem to always be fixing old, cracked wiring or adding something I would have ordered in the first place. Like AC.

[indasevens]

OK everyone---I think i got it closer thanks to ya'll--------Unplugged from fan switch and jump a hot wire into each opening that wasnt hot...blowe motor turned on with one of them and then compressor kick on with one of them..then a "low-speed fan" kicked on???? with the third?? Not sure maybe that was the lower fan if there is one??

Now on to making sure the doors al work correct....

thanks again so far so good

[indasevens]

OK thinking about it--maybe it was the lower speed of the fan and the other was higher speed...but i thought there was three speeds

HMMMM

[Andy4639]

Should be a 3 position switch well 4 if you count being off.
1. off
2. slow
3. a little more
4 high

With this said slow and a little more ant a whole lot of differance in them in these models.

[indasevens]

There was a total of four wires coming in...one was hot of course ..then one was HIGH for sure..one was med and the low AND compressor must be on one wire......Who do I need to order switch from...I know they all have them but does any support this site and I will support them...

Thanks...Now I have to run all the vacuum stuff and trace all the door opening stuff to make sure they work properly...one step at a time!!!!

[Hutch]

indasevens
This may not be revelant to your issue.
The high speed on the fan is somewhat controlled by the relay on the inside firewall behind the glove box.
If the ground from this relay is not grounded the high speed on the fan will not work
It is easy to test

[indasevens]

Thanks again for everyone and their help...Got new switch from LMC and now fuse doesnt blow and everything "seems" to be working fine...I need to put everything back together...The compressor is engageing but not blowing cold...Could be low on froen --I will have checked.....Also, it doesnt appear i have any lines going to the "vacuum"? pod attached to the a/c box in the engine compartment....Not sure how that effect everything but working through it one step at a time--thanks again