Something is going on with my electrical system and I can't seem to figure out what it is. First of all let me tell you what happened. I've got a '97 Blazer LT 4dr 4x4. My heater core had been leaking into my car so I decided to go ahead and replace it myself. I went ahead and took everything off the dash and got the dash tilted out just enough to switch out the heater core. Once that was done, I put the dash back and reassembled everything.

When I initially started the car up afterwards, it seemed a little slow and weak to start up. I also noticed my battery gauge was pretty low (just above the orange). I thought maybe the battery needed to charge up, but after driving it for a little while, the battery gauge kept getting lower and lower, until I wasn't able to go anymore. The engine wouldn't rev above 1000-1200 rpm. It stayed running but I couldn't go anywhere without it wanting to stall out when I gave it some gas.

I had it taken to the shop where they told me that it acted like a wire was either broken in the dash or there was a ground wire in the dash that had been messed up, because it seemed like a ground issue. They had checked the battery and alternator and both were fine. They were able to put a bypass bulb to temporarily-partially fix the problem. The bypass bulb was a small bulb in a socket with a black wire and a brown wire coming out of it. They connected the brown wire to the brown wire on the back of the alternator and the black wire to some plug-looking thing near the top of the intake.

Now my battery gauge reads normal, and everything seems to work ok, but I'm still missing some indicator lights on my gauge and I notice my battery gauge moves a little when my turn signals are on, but my radio doesn't seem to affect the gauge. As soon as I remove the bypass wire, my battery gauge reads very low, just like it did before. I went and took the dash out again but couldn't find any wires broken or out of place. I have no idea what or where the problem is, so I figured I'd post it on here to see if anyone had any idea or what it could be or where to look. Any help is appreciated. Thanks.

Viperguy

 

I don't have a schematic for a '97 but all I can suggest is a connector behind or underneath the dash got overlooked. it might not even go to the dash cluster itself but to the fuse box. the reason that light bulb works is because you have 3 wires going to the alternator big one one the back that hooks to to the + on the battery, 2 on the side of the alternator. small black one goes to the battery "idiot light" on the dash, brown one goes to your electrical system & senses load. the regulator in your alternator compares battery voltage (big red wire on back) to your electrical system load and charges accordingly. that light bulb between the brown wire and the back creates a little voltage drop and makes the regulator tell the alternator to put out some power. whatever that brown wire was connected to is open now. check your fuses too, one time I replaced an alternator on a Cadillac and the problem turned out to be a blown fuse in the dashboard

 

I do not have access to my wiring diagrams at the moment either, but can look when I get some time. I have to look up some 1997 fuel pump wiring schematics for someone else so while I'm in there...

 

RonJon, thanks for clearing that up a bit. I was kind of confused about how that bypass worked, but it makes a lot more sense now. I did check my fuses and all of them are fine. Also, I did go through my entire dash pretty thoroughly when I had it out a few days ago, but couldn't find anything disconnected. Am I understanding it right that the brown wire on the back of the alternator is disconnected or open somewhere, which is causing the problem.

swartlkk, yeah that would definitely help me out. Thanks.

Viperguy

 

Here ya go: