CamaroMan81

My 82 Z28 suddenly blows the instrument cluster fuse. I have tried all I can think of. Figured I would ask before I pay a mechanic a bunch of money
THANKS

SansKey

I know on my 92, the gauges fuse feed a lot of things including the instrument cluster. If that's also the case with the 82's, you may have to check a bunch of stuff.

What have you tried so far?

CamaroMan81

they are separate there is a gauges fuse and an Inst fuse. The manual calls for a 5amp but there was a 10amp so i tried but the 10 and 5 and even a 15 and it blew all of them as soon as I turned turned on the lights. Even disconnected the battery and put the fuse in and the same thing happened. Any help would be greatly appreciated

Dave

SansKey

Is the fuse labeled just 'Inst' or is it 'Inst LPS'?

The Inst LPS fuse powers the illumination of the switches and instruments. It is hot when the headlight switch is on. Does the gauge cluster illuminate when you turn the light switch on?

If they don't illuminate, then we know that it is indeed the Inst LPS fuse.

And then if it is the Inst LPS fuse, it is getting power when it shouldn't and it sounds like it's also grounding out so all that power is short circuited to ground and blows the fuse immediately.

CamaroMan81

Its labeled just INST. The gauge cluster doesn't light up at all. As soon as you pull the light switch the fuse blows.

SansKey

Alright. It sounds to me that something is touching ground and is causing a short circuit. Can you use a multimeter to check continuity between ground and the side of the fuse that goes to the instrument cluster? If it is a short circuit, you'll still have to follow all the wires to track it down.

CamaroMan81

I will check it out in the morning thank you for your help.

ghettocruiser

iTrader: (4)

Not sure if the camaro wiring is the same as the bird...but check your cig lighter socket. I kept change in my ashtray, and a dime made its way into the socket. Kept blowing the dash light fuse. And it was hard to spot at quick glance because it fits so well haha.

Might not be a dime, but if part of the inside of the socket has broken off, and shorted out, it could cause your issue. You can unplug the socket to eliminate it. But bottom line, something is shorting out.

I also seem to remember now being able to see the cig lighter being part of that circuit while looking at the schematics. But its been over 10 years since I had that problem.

J.

Lurbie

iTrader: (3)

Unfortunately, doing this will show continuity to ground for two reasons.
1. You're blowing the fuse immediately.
2. You've got a path to ground through every bulb in the circuit.
You'd be better off to find the schematics and pull the components off the circuit and add one at a time until the fuse opens.

CamaroMan81

LOL fuse opens?? Keep in mind I have no clue what I'm doing. I'm new to working on cars.

SansKey

Doing the continuity test directly from the side of the fuse holder that supplies the bulbs will tell if there is a short BEFORE any of the bulbs.

Blowing the fuse immediately gives me a suspicion that the circuit is indeed grounded at a point before any of the bulbs. This would cause a short circuit and the fuse would keep blowing immediately.

You are right that every light has a path to ground, but that path occurs only after the current is 'used' by the bulb. If the current is 'used' up by the bulb, then there is not any excessive current that would cause the fuse to blow.

This ain't a bad idear either, if you don't have a multimeter.


Ima start digging for a schematic for an 82 that we can get our noses into.

Lurbie

iTrader: (3)

OK, no problem. Simply put, a blown fuse is an open fuse. When a fuse "blows" it opens the circuit, therefore it is also called an open fuse. Sorry for the confusion.
Hopefully Sanskey has an 82 schematic, all I could pull up was an 83 with the INST. LT. fuse


I agree the short is likely before the bulb, but how would using a multimeter determine whether the short is before or after the bulb by connecting it at the fuse terminal? Without disconnecting something (like the bulbs), the path to ground is going to be measured through the short and the bulb filament, it's basically a parallel circuit right now.

SansKey

If there is a short, then current can flow directly from the battery to ground without anything limiting it. This means that a humongous amount of current will try to flow through the fuse. The fuse will do it's job and keep that from happening by blowing. If a short happened after one of the bulbs, then it's the same as the bulb's own path to ground. The bulb will limit the current from flowing and the only current that would flow would be what the bulb needs to illuminate.

So there is no such thing as a short after a bulb. That's what the return path to ground is.

If there is a short, then a mulitmeter will show continuity. If there isn't a short, then the multimeter won't show continuity.

Now a short may not be the cause of OP's problem. It could be a number of things, but the fact is that too much current is trying to flow through the fuse and causing it to blow. That makes me think it's a short circuit.

Lurbie

iTrader: (3)

Again, I agree, but my original statement and followup question was how would the multimeter not show continuity unless every bulb is removed? However, I don't mean to hijack the thread to discuss electrical theory so to get back to helping with his problem, he should start by disconnecting the components connected to the circuit. This will remove the probability of a short within a component and limit it to a wiring issue. The schematic would prove helpful, were you able to find one? I checked Mitchell, but it only goes back to 83 for Camaro.

SansKey

Yea. Back on topic. If you have a multimeter, do the continuity test, if not, do what Lurbie suggested and start pulling things out one at a time. That's a good point about a component being shorted internally. It may not be the wiring that's messed up.

I want to try to explain this one more time, and please forgive me if I keep on misinterpreting your point.
Here is a little diagram. As you can see, the bulbs don't provide a direct path to ground. Each bulb provides a resistance to the current. A direct path to ground provides virtually no resistance. That lack of resistance is what the continuity test looks for. No resistance means continuity. Resistance means no continuity.

JRODRS

not sure if this helps, but on my 91 RS i had with the 700r4, i would keep blowing the fuse. it was blow when ever i would gas it from a stop. i noticed once i changed my transmission mount the problem went away. 10amp fuse....

spyder1

did you find the problem? I have the same thing? Allan