Blowing Gauge Fuse...any suggestions kids?

[milemarker60]

I hate being on this side of the forum asking for help but hopefully one of y'all can provide some guidance. Searched for a couple of hours on the forum and am tapping out.

1997 LX450-133k miles
Issue: blowing #7 Gauge Fuse

Background: My son Mitch and I went wheeling today in his rig and at one point slid on some greasy mud into a rock hitting the front axle and causing an abrupt stop. Gauges, a/c, Windows, transmission o/d, etc all stopped working. Found blown #7 gauge fuse in dash, replaced and worked for about 10 minutes then blew again. Wheeled for another couple of hours then hit the highway home. Decided to throw another fuse in on the way home and once again worked for about 10 minutes then blew. During this time everything worked and Did Not Blow while operating any circuits...just driving down the road. About an hour later tried one more time and blew upon inserting.

Diagnostic steps so far:

-checked voltage across #7 fuse socket and shows full batt voltage with ignition on.
-checked amps across #7 fuse socket and exceeds meter ability to show...checked other fuses which fell into expected ranges. Clearly a short.

Started disconnecting circuits supported by this fuse and left offline as I progressed:
-a/c plug-line pressure switch in front of batt
-a/c control head on dash
-CDL dash switch
-Park Neutral Switch
-reverse bulbs
-trailer harness plugs in RH rear quarter
-light harness plugs in LH rear quarter
-cruise control
-aux/rear heater fan dash switch
-power window & lock switches all doors
-inspected harness by EGR and appears AOK...heat wrapped with no signs of deterioration.

I'm clearly not finding the short by just unplugging these circuits. Found it odd that it would support a fuse for 10 minutes twice then progressed to an immediate shorting situation.

Any help would be greatly appreciated.

Dave & Mitch

 

[zachwalker18]

My 94 Cruiser was blowing this fuse. I still had the spare in the factory location at the time and after bumping something off road, it had pushed against the wiring for the trailer lights. This caused the wires entering the right rear fender well (under the truck) to rub on the metal through the grommet. Long story short, after I fixed that problem, my dash lights all started working again.

I know you hit on the front, but is there a chance the tire was jarred and messed something up back there?

 

[Sc0-]

One of the plugs or wiring to the plugs on the transfer case? (Had this problem with my rig.)

Cigarette lighter plug or wiring?

Fusible link?

 

[Tools R Us]

Check the main engine harness where it passes the EGR pipe.

 

[milemarker60]

Thanks for the quick input guys.

I pulled the heat wrap and covers off the harness by EGR and all looked great with no discoloration or brittleness detected.

I disconnected the trailer harness inside the rh rear quarter prior to its exit thru the body effectively taking it off line.

I unplugged, cleaned and re-seated all connections to the transfer case, transmission including the park neutral switch and CDL switch.

Cigarette plug is on a different fuse and all good.

Fusible links all good.

Took the alternator out of the system...no change.

Forgot to add earlier, I also unhooked the actual Compressor and Clutch, not just the pressure switch.

No Joy. I'm racking my brain as to what could have shorted after taking a hit/sudden stop. And on top of that, why it started as a slow burn to an instant blow situation for the fuse.

Electrical is tedious but typically not that big of a challenge so long as you can trace the circuits. Am I missing any other feeds that this fuse supplies power too? I commend this rig, it takes a lot to frustrate me and it has succeeded.

I have not pulled the instrument cluster but figure it may as well be next.

Keep the ideas coming.

Dave

 

[1973Guppie]

I would look closely at the panels that got shifted off roading and what is attached to them. It's there you just gotta find it.

 

[milemarker60]

Not the instrument cluster.

Hit the front axle/Dif...slid into. Pretty good jolt. Front and real lockers continued to work but on different circuit. CDL disengaged via dash switch on one of the 10 minute functional times once on the way home. Obviously this does not work currently since tied into fuse #7 too.

 

[milemarker60]

Well, took the fuse box out from behind the lower dash panel. Identified the two yellow w/ silver bands on one side and a much larger gauge black w/ silver stripe on the back of #7 fuse. Traced them into kick panel but found nothing out of the ordinary. Unplugged the associated harnesses, wiggled them around and plugged back in.

Short went away and all is working again. I'm not holding my breath that I've solved the issue but I must have found the offending area. I'm guessing it will pop again while Mitch drives back and forth to school in the morning.

 

[JayhawkFZJ80]

Milemarker60,
Any luck finding the issue with the blowing fuse? I have this issue and not a clue where to start hoping someone has figured it out already

 

[86tuning]

I'm a bit late to this party, but the general method for diagnosing dead shorts is to install a bulb in place of the fuse. The bulb will glow brightly while the short is still there. Then disconnect the circuits downstream of the fuse one by one, until the bulb goes out....

Works well for Dome circuit where there's like a hundred and eleven items running off that one fuse.

I have a bulb with two wires on it that I plug in place of fuses. The proverbial test light. Also works for verifying power to motors (power windows) and whatnot.

 

[GeoRoss]

I'm a bit late to this party, but the general method for diagnosing dead shorts is to install a bulb in place of the fuse. The bulb will glow brightly while the short is still there. Then disconnect the circuits downstream of the fuse one by one, until the bulb goes out....

Works well for Dome circuit where there's like a hundred and eleven items running off that one fuse.

I have a bulb with two wires on it that I plug in place of fuses. The proverbial test light. Also works for verifying power to motors (power windows) and whatnot.

I'll have to use that. I've got a dome circuit short. I have it narrowed down to the actual dome light or door switches. Your method would have been faster.

 

[Red Merle]

I had this problem. Mine ended up being that one of the connections for the clips that go through the firewall right below the brake booster was loose. I squeezed them tight and haven't had an issue since but I fiddled around for a month before I figured it out.

 

[gummycarbs]

I'll have to use that. I've got a dome circuit short. I have it narrowed down to the actual dome light or door switches. Your method would have been faster.

Take the cover off the dome light and take a look at the metal strips inside. There's one going right to left that, if it gets pressed and bent, grounds out and blows there fuse. I fixed it with a strip of electrical tape between the two.

 

[JayhawkFZJ80]

Take the cover off the dome light and take a look at the metal strips inside. There's one going right to left that, if it gets pressed and bent, grounds out and blows there fuse. I fixed it with a strip of electrical tape between the two.

thanks i'll look at that.

 

[DanMedeiros]

I had this problem. Mine ended up being that one of the connections for the clips that go through the firewall right below the brake booster was loose. I squeezed them tight and haven't had an issue since but I fiddled around for a month before I figured it out.

You are a life saver! I had this exact some problem and I just tried unplugging and plugging back in the same connector. Magically it all works...for now

 

[Red Merle]

You are a life saver! I had this exact some problem and I just tried unplugging and plugging back in the same connector. Magically it all works...for now

You are about the 4th person other than myself that had the same issue. Glad yours is fixed! Mine has been good for almost 2 years.

 

[ZackR]

I had this problem and it was a short in the speed sensor that provides signal to the speedometer (glad you found the fix, this is for future reference).

 

[Kylesparx]

Looks like I'm joining the club here.
GAUGE fuse is blowing instantly when I turn the key to ACC.
Glad to find this thread with so many suggestions.
Let the trouble-shooting begin.

 

[bootlegger]

Member now also. Mine started intermittently and now is constant. Supposed to rain tomorrow and my windows are half down...arghh

 

[Burt]

Member now also. Mine started intermittently and now is constant. Supposed to rain tomorrow and my windows are half down...arghh

Just started happening with our 97 LX450. Seems to hold for a little while but blows when put into gear.