Weird Electrical Problems
 

Hey gang,

So I have a conundrum for your collective brains.

I just purchased a 2000 Blazer from Craigslist. Mechanically and aesthetically it's sound. Electrically it's a nightmare.

The primary problem is I can't get the A/C clutch to engage. Before I determined it was electric, I replaced the compressor, the evaporator, the accumulator, the expansion device, and the low pressure (on the accumulator) switch. I've tried jumpering the high pressure switch, the low pressure switch, and the A/C relay in the fuse box, and every combination therein, and still no luck. If I run power straight from the battery, the clutch engages. When the car is off, I can jump the relay and the clutch will engage, but not when the car is on.

Additionally, when I looked at the fuse box, there are several relays/fuses that have been wired together with jumpers. Not knowing what these did, I pulled them out. Turns out that one of them was making the fuel pump work (jumper from F/Pump to Eng 1).

The other jumpers are from HDLP Pwr to RTHDLP, and from RTHDLP to LTHDLP. These make the headlights (and corresponding interior light change) on all the time. The only thing the interior headlamp switch does is make the headlights dimmer (when I turn them off) and the dimmer switch works.

Before I pulled the jumpers, the LED interior accessories (gear selection, odometer, and stock radio display) all flickered, but when I replaced the jumpers it was fixed. This could be because one or two of them were loose and now they're not.

So what do you all think? There is sufficient pressure in the A/C system to cycle the clutch on (verified with manifold gauges), but nothing.

The previous owner bypassed the security feature of the truck--apparently he was having problems with it for some reason.

Everything else on the truck seems to work. The lights all work and come on when they're supposed to, the cruise control works, etc. The speedometer reads a little faster than actual speed (per my GPS), but only about 10-12%.

Any ideas? I'm thinking it's the fuse box itself. Could a bad fuse box be causing all these problems? Or do you think it's the computer?

Thanks for the help! Sorry for such a long post.

The fact that there was that many jumpers in the fuse box is scary to me. Run while you still can.

New symptom this morning: Now it's stuck in 4Lo. Could this be related to the other problems?

Too late to run now. And it was only 3 jumpers.The truck runs fine other than that.

I would bet that there is a problem with the ignition switch. Get a multimeter and test the continuity of the contacts in the ignition switch at the harness under the steering column (accessible by removing the hush panel & knee bolster from under the driver side dash) using the information found in the link at the bottom of my signature below. It shouldn't take you more than an hour start to finish to test all of the contacts in the ignition switch and you'll know whether you need to replace it or not.

Well, I don't have a multimeter, but I pulled the old one and it had some carbon buildup, so I decided to replace it. No dice. Still stuck in 4LO, still no AC, and still the weird electrical problems.

I'm getting frustrated at this point...

So instead of buying a $30 multimeter that you could add to your tool box, saving you money elsewhere on down the line, you bought an ignition switch to the tune of ~$60 that you didn't need... Makes sense... :icon_doh:

At this point, I suggest you get yourself a factory service manual, a multimeter, and perhaps a good exorcist. It's time to dig into the systems that have been screwed with and see where the faults lie. At this stage, I offer a hearty good luck to you.

When you only have a few dollars, and buying a tool PLUS parts isn't an option, you roll the dice. This time I lost. Sorry but I don't have all the money in the world.

Thanks for the help.

Well, finally got the truck into 2HI. There was a fuse getting blown (ATC) every time I tried to shift the transfer case. Burned out 3 20-amp fuses getting it out.

So now I'm back to purely an electrical problem. Guess that's what I'm doing this weekend. Anyone have any idea where the problem might be, so I don't have to tear the engine wiring apart?

They will drive you crazy!!! Just gotta plug away, you get good advice here, just gotta get a bit closer to what exactly it is.....people here are pretty helpful

Let me ask this question then: Is there a circuit common to the A/C, 4wd, and headlights? Or could it possibly be a bad fuse panel itself?