Need the Electrical Expert - Blowing Gauge Fuse

[jdub]

This is driving me nuts...the gauge fuse runs a whole list of stuff besides the combination meter. The fuse is blowing when I turn the key and I need this fixed.

Background - Fuse 1st blew cruising at 70 MPH...nothing unusual. The car dropped out of overdrive (auto tranny) and all the dash guages went to zero or froze, except the speedo. I pulled over and replaced the fuse...it was fine until I cranked the car. Fuse blew again after a few seconds.

I thought it was my Tach causing the problem...it bounced from zero to running RPM before the fuse blew again. I got a known good combination cluster from a friend and tried it. Fuse blew. Removed the dash cluster and left all connectors disconnected, replaced fuse...fuse blew again.

I have went down the power source list in the TRSM, disconnecting the various things this fuse powers....AC fan relays, heater VSV, overdive switch, neutral start switch, rear light failure sensor, climate control, etc. No luck...fuse blows everytime I turn the key on.

So...this is maddening. I'm thinking it's a short in the harness somewhere and guess I'll have to test each wire. I wanted to ask any electrical guru out there if I may have missed something or a suggestion.

Any help is appreciated!

 

[supra90turbo]

Unfortunately, you will need to test each wire.
Not every single wire, just the ones that get fed from that fuse.
It's gonna suck, but it's the only way.
Bare wires + very sharp dash bracing = electrical short.

 

[jdub]

Yeah...come to that conclusion too :3d_frown:

This fuse feeds through several connectors on J/B 1 (left kick panel). If I disconnected each one at a time, replacing the fuse as it blows...would that help narrow the harness down causing the problem?

 

[PIONEER]

which fuse is it? Also have you had any engine work or worked around the engine bay lately?

 

[jdub]

It's the 7.5 Amp gauge fuse.

I installed the EGR to pass emissions...non-CA car...no EGR sensor.

 

[PIONEER]

It's the 7.5 Amp gauge fuse.

I installed the EGR to pass emissions...non-CA car...no EGR sensor.

Make sure the clip that holds the harness on the manifold is in place. I had a similar problem where the harness was touching the manifold and eventually the outer plastic burned through causing a short in the harness. My car would do the same exact thing. Turn the key, lights would come on for a second and Boom, all dead. took me about a week to figure it out.

 

[chriso]

I had a problem with my gauge fuse blowing also. I thought I had it traced to a corroded/oxidized connector on the back of my combo meter (you should check and clean all of them). It turned out I had a loose fuse in my fuse block (due to a fuse tap when I originally bought the car). I could mimic the fuse blowing by moving it back and forth in the fuse block. Also make sure that if you have any add-ons, fog light rewire, boost controller, turbo timer, etc... that they are on a power source that is fused and not tapped off a fuse block fuse.

The moral of my story: Don't use fuse taps !!! They enlarge the fuse holder clips and cause a bad connection.

 

[Idealsupra]

check your reverse light wires....

i had the connection cut and the wires i thought were taped up but it came undone and starting grounding against the block every now and then blowing out the gauge fuse and the windows and seats wouldnt work either....so check that out

 

[Asterix]

Easy check: make sure your engine block ground wire is well connected. Take it off and sand the terminals, block, and body with 220 paper and reinstall. Some anti-oxidant goop is good if you have it.

The clue to me was when you turn the key to start the engine. The starter return current tries to get back to the battery through your gauges, which doesn't work very well.

Asterix

 

[jdub]

Thanks for the suggestions guys...The fuse blows as soon at the key is turned to IGN. It's gotta be the harness grounding some where...I took the guage cluster completely out (ckecked the connectors too) and the fuse still blew.

:3d_frown: This is really starting to piss me off!

 

[Idealsupra]

Thanks for the suggestions guys...The fuse blows as soon at the key is turned to IGN. It's gotta be the harness grounding some where...I took the guage cluster completely out (ckecked the connectors too) and the fuse still blew.

:3d_frown: This is really starting to piss me off!

check your reverse lights wires! and the vsv wires also!

 

[jdub]

Found the problem Guys!

Pioneer - you were dead on man - my main harness was melted through. It was touching the EGR fitting on the intake manifold. Three wires were melted...one was the RPM signal wire from the igniter feeding the tach....that explains the erratic tach readings.

At JJ's suggestion, I rigged a "test light" using a side marker light with a pair of spade connectors. Then I plugged it in to the gauge fuse holder on each side. The light was dim...it should have been bright with an active short. I tried a couple of parts (VSV, reverse lights, etc), then I went into the engine bay and moved the harness in the area of the EGR. The light went bright!

The melt through was very hard to see...it was about the size of a pencil eraser. I taped up the melted wires and added heat shield tubing over the repair. Everything was back to normal.

I appreciate all the help! :biglaugh: