A/C Blower fuse keeps blowing
 

I have searched and found a few things but i still cant locate the cause.

1989 S10 Blazer 4x4 with A/C

Ok so this started about a month ago. I thought maybe it was the compressor cycling on an off because of low freon. I unplugged the compressor replaced fuse. Did not blow right away. Once it blew again i then looked for shorts with no luck. I replaced fuse and tried to figure out what action causes it to blow. It doesn't seem to be easily reproducible. It just pops occasionally.

I removed the blower motor and found that it was not working unless i shook it or tapped on it. I replaced the motor with new unit hoping it was the motor causing it to blow fuses. Worked great for about 5 min then the motor stopped. I checked fuse it was good! I checked ground, it was the problem. When i adjusted the ground screw it sparked and then started to work for another 5 min and then popped the fuse again while driving. I then took ground wire off and made sure i had good contact. Replaced fuse again and it worked for a day and this time popped when i moved switch from vent to a/c (knowing a/c comp is not plugged in).

Any ideas on where to look first. Should i still suspect the ground? The new blower motor is coated with black paint, which i wonder is causing problems with the ground. I can live without the a/c but come winter i will need the blower to be fully operational.

What fuse is this exactly? I do not have my references at work with me, but I can check it when I get home.

25A a/c - heater blower motor fuse? Not sure what you are asking? Its in the fuse bank in the drivers kick panel area. It is the last fuse in the middle row.

Any ideas on this?

I have kept the blower motor and the a/c comp unplugged and the fuse still blows with no load on system. It does not blow right away. I still cant determine what action is causing the short.

My next guess is to replace the resistor pack and maybe the blower relay. I have not been able to locate a short through my testing.

I would be looking for any chaffed or pinched wiring under the dash and in the engine compartment. Sounds like you have a wire on that circuit that is grounding out. It likely will be under the dash between the fuse block and the HVAC control head where the fan controls and A/C on/off are.

Ok i bought 25 more fuses to keep looking for a short or better determine where the issue is.

I did notice that the red power wire from the distribution block on firewall that enters the blower relay harness gets very hot (as does the harness). None of the other wires (from resistor pack or the purple wire to blower motor) gets hot at all. I have also noticed that the blower does not work on the very lowest speed now.

I un-loomed all the wires under the hood that has hvac wires. I was getting the fuse to pop, but i couldn't determine if it was me moving the wires or the overheating relay. It seemed very tied to the timing. If i immediately replaced the fuse it would blow. If i waited a few min and replaced it would be fine for a few minutes. It would pop when i was playing with the wires, but never the same wire twice. I put the last fuse in with even more wires unloomed and was just going to wait for it to pop without me fooling with it . . .it never did.

So far it has not popped and I have majorly played with the wires and driven 30 city miles. The power wire gets too hot to touch still and again the low speed does not work.

I think i will replace resistor pack and relay pack, and wait for it to blow again and then resume my search for the short if it turns out to not be resistor or relay.

Any other ideas?

My 1991 S10 Blazer is doing the same thing.
I recently built a new engine for it and paid a guy to R&R the engine (I have a bad back and couldn't do it myself). Suffice it to say he was no where near the expert he claimed to be. I have had to continually redo parts of a proper engine R&R. The latest problem was the improper installation of the driver side exhaust manifold gaskets. At less than 3,000 miles the gasket burned through and I couldn't stand the ticking noise and it made my new engine sound like crap. So I had to pay a shop to replace the gaskets to the tune of 3.25 book hours, because the whole power steering assembly had to come off to get to it.
So I paid them, the engine sounded great again. As soon as I left the shop I went to a convenience store up the street. The entrance has a bump and when I hit it the 25 amp A/C fuse blew. I went to a auto parts store and bought fuses and put in a new one. It blew as soon as I turned on the A/C. I had to pick up my kids so I couldn't mess with it anymore. Later that night I replaced it again and this time it worked fine, until I closed my door at which time it blew again. I put in another and it blew immediately. I left it for the evening. The next day I put in a new fuse again. This time I didn't turn the A/C on till I was driving down the road. It came on and was working fine. I came to a stop light, it was still working fine, until I pressed the gas to take off from the light at which time the fuse blew again. I was pretty fed up by this time and took it back to the shop because this had never happened until I had them work on it. They ran around testing everything with a voltage tester and blowing multiple fuses. They told me it was the blower motor, because with it unplugged the A/C compressor would work fine, but the moment you plugged in the blower the fuse would blow.
So I went and bought a new blower motor and installed it. I put in a new fuse and backed out of my drive way with the a/c working and happy. That is untill I put it in drive and stepped on the gas, at which time the fuse blew again. I drove to the auto parts store and bought a new pack of fuses and I bought a new blower motor relay. Installed it and that didn't help as it blew the new fuse as soon as I turned on the a/c. Next I went inside and bought a new resistor pack and installed it. It still blows the fuse.
As you can see I have the same problem and I'm about to pull my hair out. It is November, but here in Tucson Az I still need my A/C because it is still in the upper 90's.
Please any new insight would be greatly appreciated.

Jim

Update to my 91 S10 blazer. It doesn't appear to be isolated to the blower motor. I had the blower motor unplugged and when I turned on the A/C switch it blows the 25 amp A/C fuse as well.

Please help us.
Thanks
Jim

1) Have you checked your blower switch?
2) Does your blower motor work on high but not low, Medium 1 or Medium 2? The blower on low, M1 & M2 run off of the A/C fuse while on High, it runs off of a different fuse. Actually, it runs off the junction block which is "fused" with a fusible link off the alternator. I'll check my wiring diagrams. Had a similar problem. Once you have a diagram and see how the system works, it's pretty eady to figure out. I bought my 94 with several issues related to the A/C and blower. They're all fixed now. The resistor pack is easy enough to just look at and see of it's a problem. Watch out though, it gets like REAL HOT. I can see you guys haven't posted in a while so I hope you got it fixed. If not, post again. I have (unfortuneately) lots of experience with this system.

My status remains below. I have the new resistor pack and heater relay, but have not installed as it is currently working (except on low). Before i started fooling with the wires trying to locate a short, all speeds worked. I am hesitant to get back in there right now with the cold weather, as i dont want to lose heat due to continuously blowing fuses.

I still suspect a short, as it has not blown the fuse after i unloomed everything under the hood having hvac wiring in it. I hate not having it loomed but until i can be certain it is fixed, its going to have to stay like this.

You definitely have a wiring problem if things are back working to a certain extent. It is just a matter of finding it. Not having low speed though could still be the resistor pack.