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Virtual Wrench
Virtual Wrench, Chevy Mechanic
Category: Chevy
Satisfied Customers: 14620
Experience:  35 years Master Mechanic
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1997 Blazer: blowing..dim indicator as if low voltage..circuit

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1997 Blazer. fuses for directional, brake blowing #1, 3, & 16 on fuse panel). When using directionals (at times) no flashing but dim indicator as if low voltage to circuit (high amps=blown fuses). Intermittent but more when brakes are applied. More occurance when main head lights are on. Any suggestions? All lights work OK.
Try disconnecting the brake light switch and see if it still blows a fuse. Do you know where it is located?
Customer: replied 10 years ago.
Reply to Virtual Wrench's Post: Situation exists even when brakes are NOT applied. Removing the brake light switch is same as NOT using brakes for test purposes, correct? Issue appears to be supply to lighting group. When more amps are pulled the fuses will blow. The fuse does not blow when brakes applied or when directional signal is used. When all are used together for a long period, fuses blow (3 fuses as once).
I was suggesting that the brake light switch could short out intermittently with OR without using the brakes. If you like i can get you a wiring diagram for the system if it will help. I suspect a ground issue, being that the indicator is dim.
Customer: replied 10 years ago.
Reply to Virtual Wrench's Post: It sounds like the ground might be the problem. A wiring diagram would help, please send. Would a poor ground cause amp spike to blow fuses? Is their a common ground to this group? I know, two many questions for these pain in the @#$% type problems. Will be standing by for diagram.

yes electrical problems are bad enough, trying to diagnose online is very challenging Undecided I forgot to ask is it a S-10 blazer or full size?

Customer: replied 10 years ago.
Reply to Virtual Wrench's Post: Full size Blazer with A.C. and all the added electrical devices, four wheel drive, automatic, etc.

By full size I mean it's not an S-10 Pick-up but a Blazer on the s-10 chassis (I guess).

Thank you for the info.....i'll see what i can pull right back

Here you are, in my opinion it is probably the "Body Control Unit" (BCM) at fault.




Hope this helps!

Virtual Wrench and 5 other Chevy Specialists are ready to help you
Customer: replied 10 years ago.
Reply to Virtual Wrench's Post: I pushed the wrong button and do not accept the last answer. The BCU (body control unit) costs $410 and is rarily sold by the local chevy dealer (two units in the last year).

Hello David, sorry about that. Contact Just Answer Admin and they will refund your money. Your original question was "Do you have any suggestions" I offered many.

Thanks and good luck


Virtual Wrench and 5 other Chevy Specialists are ready to help you
Customer: replied 10 years ago.
Reply to Virtual Wrench's Post: Hi Larry,

Thanks for your try. I didn't mean to sound harsh with the last one, I just pushed the wrong button in haste then checked with Chevy parts. I guess I'll take the vehicle to the dealer. I can't guess with $400 parts. I'll will click accept next time the buttom is available. You tried and you're entitled to be paid for your efforts. Any chance of getting a full electrical wiring diagram through you? I'll try to trace other possible weak links on my own. Thank again and it was worth the experiment. David Kantor, Seattle WA

I completly understand. I wouldnt shell out $400+ either unless i was darn sure it was going to fix the problem. Unfortunatly i don't have a full diagram, but i might suggest the Library, as they have a pretty good selection of repair manuals there, they wont let you check them out but you can make a photo copt of it.

Best of luck my friend!


Customer: replied 10 years ago.
Problem turned out to be a towing wire harness. It was getting rained on and may have been poorly installed. FYI

Thanks David! I was going to ask you if it had the trailer wiring, but the thought got lost in the mix. Sorry,,,I should have mentioned that.

I'm glad you got it figured out, and thanks for asking!