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AC Blows Fuse

2K views 10 replies 5 participants last post by  highfigh 
#1 ·
Hello world I bought this van 6 months ago and have replaced many components to get the van running smooth again, it is a '97 GMC Safari RWD
Today I begun my quest to restore the AC System, we have a heatwave going on in the west coast, and I feel like yesterday's leftovers inside the microwave whenever I get inside the van.

Turned the AC switch to all knobs and none blow air.
Engine Bay Fuse = OK Relay = OK
Fuse #12 @ Driver's Footwell = blown (20A HTTR-A/C) , replaced turned on AC , something inside the dash briefly made noise then fuse blew

Next step, I will take a gander at a wiring diagram and see what's connected. I love showing my progress to you guys :dance: :whistle: Let's get that AC running!
 
#3 ·
Read resistance across the contacts on the blower motor. Sounds like a classic seized blower.

Note that if it had never been changed before you will have to cut and remove the dust cover from it. There are plenty of threads on this here…. It's just confusing if you don't know to look for it.
There are actually cut lines traced on the cover, when you remove it the part you remove will look like this.
78A534CC-CBD2-4A76-8EA6-544906B0ED32.jpeg
 
#4 ·
AC/Heater Wiring Diagram, circled the key items in red. (From a 1998 model)

HVAC Control Module - Houses the knobs, located in dash
Temperature Control Motor - Do not know the loc. of this component :shrug:
Blower Motor Resistor and Relay Pack - Located in area under receiver/dryer
Front Blower Motor - Located under in area under receiver/dryer
G100 - "In the right front of the radiator support next to the engine coolant reservoir"
G200 - "In the right front A pillar above the right front door jamb switch"

I doubt the grounds are causing the fuse to blow (as other fuses would also blow).

Sailing_Faith said:
Read resistance across the contacts on the blower motor. Sounds like a classic seized blower.
I suspect this or even more likely the BM Resistor and Relay Pack

Where is the location of the Temperature Control Motor?
 

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#5 ·
Update: Swapped Blower Motor Resistor and Relay Pack with a junkyard part, turned on van/turned on Ac = Screeching from blower motor, gave it a few whacks and AC Blows only from defroster vents!

Problem solved no more blown AC #12 fuses

Next we gotta fix that vacuum problem (start new thread? Or we can possibly hammer it out here.)

Here's the issue, the following photo has 4 points of interest
1. Group of 3 vacuum hoses that go through firewall
--Top left connects to check valve
--Top right connects to. ????
-- Bottom connects to item next to condenser
2. What the hose looks like
3. Vacuum Canister Larger opening missing a hose
-other hose connects to check valve
4. Pair of hoses that are not connected to anything, they are labeled "FPDM ABG" most likely the #2 plug goes into the #3 port ( I tried it did not fit)
Check valve = all 3 hoses connected
 

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#7 ·
keith92ext said:
Check the line going into the intake manifold .. gonna have to take dog house off .. gets brittle from the heat .. it's a small elbow
Sometimes I get a little extra on diagnosing, the fix was similar to this.....it was incredibly simple once I knew the correct routing of the hoses.

The check valve has 3 hose connections. The black tip hose goes to the manifold, opposite that tip goes to the firewall and the "bottom" tip goes to vacuum ball.

My setup the last 2 hoses were switched....the "bottom" went to the firewall. So I simply switched the hoses and air blows from the vents!! (Hot air) Oh, previous owner what were you doing? :lol: :lol:

This takes care of my vacuum issues [[I guess that vacuum ball has an open port for venting?]] Now comes the fun part, took out the manifold gauge. (The compressor does engage) :bouncy: and read 27 psi on low-side, 0 on high. This one should be walk in the park
 
#8 ·
I thought I was out of the woods, swapped blower motor and the control unit and fuse #12 began to blow again. Disconnected all items including the sensor on the receiver/dryer and plug that goes to compressor. After blowing a few fuses, I discovered that the compressor is blowing the fuse. That 2 pin connector that you access from the doghouse area.

I'm aware that the compressor has a diode inside, any advice before I spend on a new compressor?
 
#9 ·
UPDATE: Woooo figured it out :banana: The previous owner put in a new compressor, but installed the wrong refrigerant pressure switch behind the compressor.
This guy right here >>> https://www.rockauto.com/en/moreinfo.ph ... 83&jsn=883

The connector wouldn't even snap properly onto it, sometimes it would connect and sometimes it'd be dangling for life....whenever it did make contact with the 2 pins, instant AC fuse blown....amazing, that's what gave me the false reading regarding the blower motor. Time to recharge this sunofagun and feel that ice cold AC
 
#11 ·
I bought my Astro on Craig's List from a guy in Phoenix and he contacted me to say that his guy couldn't find the cause of the AC fuse blowing when the control was set to ANY AC function, including defrost. Knocked off $800, too.

Turned out that the HP switch was the cause- maybe AC compressors don't last long enough in extremely hot places for the switch to short.
 
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