Originally Posted by Jim-in-AZ

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

Originally Posted by Flores

Hello I stumbled across this forum looking for answers to my problems. My 1991 S 10 blazer with a 4.3l was having similar problems. The 25 amp fuse keep burning out and the fan would quit working. After reading the posts here, I had a good place to start. After replacing my noisy fan it still would blow fuses occasionally if the rpm's were increased or I hit a bump. That was when I figured it had to be a short so I bought a 25 amp breaker and had a friend install it wile I was looking under the hood by the heater box. That is when I noticed a puff of smoke and the breaker popped. I pulled the breaker and the negative battery cable. Eureka I found my problem. On the passenger side of the engine is a thick wiring loom. it travels along the valve cover when it gets to the end of the engine it turns and goes down the firewall. That is were the problem was the plastic loom was deteriorated and mostly gone and the wires were rubbing on the engine lifting eye. after repairing the wires that were damaged I bundled them in a piece of old radiator hose and zip tied it together. I replaced the breaker and the rig has not had any more trouble with fuses the A/C works and the fan runs great. I know the posts are old and this response may not help every one. But this thread helped me find a starting point and hopefully my post will help the next person find their problem quicker. The factory probably ran all the looms this way and thought the plastic looms would protect the wires, but with the age of these rigs and the heat of the engine the looms disappear and the wires are exposed in a spot that is hard to see let alone find.