Gauge fuse blown out

[bowtiefreak383]

I haven't really had a chance to troubleshoot it yet, but my gauge fuse blows out as soon as I turn the key over.

Think it could be a bad gauge or a short in the harness somewhere?


Thanks for any info!!

[Pontiac1976]

Something shorting out in the cluster wiring or cluster board.
What year truck did you have, and did you change the cluster or move anything around there. Have you added anything to the fuse box that might be shorting against the gauge fuses. have they all was worked. or did you just find a fuse blow-en put in a new one . If the last one is what happened some one might have did some wiring.
right now that as much help that I can think of need more info.
try to check rule out some of these things.

[bowtiefreak383]

1987 TBI 350 (really a 355"), (383" once upon a time)

I do have an inexpensive tach wired to the fuse box, but I've looked at it closely and made sure to not have any wire-to-wire or wire-to-metal contact anywhere.

I've had the dashboard off several times in the past, but I've never pulled the gauge cluster out (yet!).

I did forget to mention that I have intermittent power giong to the fuel pump and to avoid being left broke down somewhere, I currently have it set up with a toggle switch.

I've finally settled down with a stable job so I can really hunker down and concentrate on these issues and not throw a band aid on them.

I will be cracking open my GM manuals for assistance, but I was trying to possibly narrow down my range of possibilities.

Since my ultimate goal is to convert over to an LS1, I don't want to shell out $$$ for a new wiring harness.

Thanks for the help!!!

[Pontiac1976]

This might be dum question but do you have the tach & fuel switch hook up to fuse or something taped of the gauges line.
The other big thing is "Grounds" check all your grounds in the motor bay, from motor to frame and frame to body. under dash there should be a ground bye the driver door headlight part of the dash door post make sure it good there to.
are you using a relay for the fuel pump switch . Might be over loading the fuse there ( fuel pump should be 30 amp fuse )
I think that were the problem might be. you must have a bad ground at the tank some where if you bye passed the fuel pump to a switch or relay.

[bowtiefreak383]

Grounds seem to be ok. I'm just gonna have to start opening the loom and start troubleshooting.

Is there some way to determine if a gauge is no good? Seems like I've heard someone talk about using a meter on the gauge itself and depending on the reading (infinity, etc...) you can trace down a bad gauge. I'm still doing some r&d on this before I tear out the gauge cluster

[Highpsi]

If you have the schematic, you can determine which printed circuit location on the back of the cluster is 12 V source. I would run a jump wire with same rated fuse inline to that connection, and see if the fuse blows. Then you begin to narrow it down to the cluster or the harness.

[bowtiefreak383]

[bowtiefreak383]

Well, I don't think my problem is anywhere in the cluster. With the gauge cluster connector unplugged, I still blow out the 20amp fuse when I turn the key on.
Next I'm gonna disconnect the harness connector at the firewall just behind the fuse box. From there check all circuits for resistance from the connector to the gauge senders.

1 - Coolant Temp Switch in driver's side cylinder head
2 - Oil Pressure Sender in block above the oil filter
3 - Voltmeter circuit from alternator
4 - Fuel tank sender in tank(may have to drop the tank if all the others give me a good ohm reading.

According to the GM manual:
The coolant temp sender in the intake next to the thermostat housing is wired to the ECM only. Also the oil pressure switch mounted on the back of the intake next to the distributor is also wired to the ECM together with the fuel pump.(If the ECM reads low or 0psi oil pressure, I think the fuel pump will be turned off)

Does this sound like a logical approach or am i making too much work for myself? I'm not in anyway an electrician, and this is the first time I've thrown myself at an electrical problem by trying to fix it and not bypass it.

Any more tips will definitely be appreciated!!!
And I'm thankful for the help so far.

[Pontiac1976]

OK in your owner manual what fuse is blowing"what all on that fuse".
Oh is that the right fuse that that goes in there. What the manual say.

I would check all the stuff is listed on that fuse from one end to the other end.
I am then sorry to say it but grounds or bad positive are the #one thing for stuff like that.
Two many thing on a fuse line can do it..