Instrument Panel keeps blowing fuses...

[bgtaylor]

About a week ago I was fiddling with the cigarette lighter, to see if it actually works. Unfortunately when I plugged in the lighter and it immediately blew the fuse for the instrument panel. I have recently taken apart the instrument panel until I reached the gauges and found the bulbs are still functional but it continues to blow the fuse... Now I'm stuck the in the troubleshooting phase and have no clue where to look to find the probable bad ground. Thank you to all who spend the time to reply with any advice. It is highly appreciated. I'm getting tired of turning on the dome lamp to read my speedometer!

Thanks again,
Brian.

[bgtaylor]

Also, is there any way to test to see if an actual gauge is still good because my temp and fuel gauge don't even budge and I have them taken out right now.

[sman]

3rd gen temp and fuel gauges are notoriously flakey. When/if you put them in the cluster tap/hit them with the back of your knuckle or hand and they may start working. Just need replacement, not sure what goes on that makes them quit.

[TrickyTransAm]

I guess there's a couple ways you can approach this, but need more information.
Please be descriptive as you can.

I'll have to look at the wiring diagram for an 85 to help a bit further, but it seems odd that the Cigarette lighter would pop the dash light circuit. Usually that is on a separate circuit because it draws roughly 10 amps at full current.

Does it only pop the fuse when you plug in the lighter? What about an accessory such as a phone charger?
Or does it pop the light circuit only when you pull the switch for the dash/Park lights?

Double check the back of the cigarette lighter socket to make sure the positive center post isn't fractured off and shorting to ground.

Another approach... Pull the light switch out and pull off the connector. Check your wiring there - Do you have voltage at the appropriate leads? Then use a small jumper wire and only connect the circuit for your Dash lights (removing the parking lamps from the equasion) - Do you blow a fuse? If not... Jump positive voltage to the parking lamp circuit on the switch harness... Do you blow a fuse?
That will help you narrow down parking vs interior lights.

The other thing you can do is pull out your cluster and check the wiring coming TO the cluster.
The gas guage, and fuel pressure should ohm out at something other than infinity (From memory, I believe 5-80 ohms, but need to double check with someone with a manual)
Voltage is easy - you should read battery voltage with the key in the "On" position.

Checking Guages:
You need to use a multimeter and ohm check the guage leads - they should read some form of resistance around that 5-80 ohms. If they read nothing across the coils, you have an open coil (Dead guage). Be careful with these - they are very fragile instruments and the needles are brittle.

One other thing I thought of.... Do you have an aftermarket Radio? Are you sure your Illumination lead on the radio is solid and not shorted out?

Let me know some more details and I'll try to get you up and running!
C

Oh...BTW - Do NOT USE CHEAP Unbranded Fuses such as those from Harbor Freight. These fuses have been recalled numerous times and CAN start your vehicle on fire.

[bgtaylor]

The fuse only seems to blow when I attempt to turn on the instrument lamps. As long as I have them turned all the way down, it will not blow a fuse when I turn on my lights. The fuse for my radio also seems to be on the same circuit because when the fuse does blow, my radio receives no power. I will go into it more tomorrow. At the initial point of this problem starting I was just checking to see if the socket worked by plugging in the cigarette lighter and it sparked and blew the fuse. I since then have disconnected the outlet all together because I don't want any power drawing out while I'm working, also preventing any chance of a fire hazard. Like I said before, It only blows when I attempt to turn on the lamps by twisting the light knob. I'm not sure if I can take out the light switch but will try tomorrow. I'm hoping its just a positive and negative/ground touching so that it my be easily fixed. I have also bought new fuses from AutoZone. I believe there Bussman or something like that. I just don't understand why the fuse would blown from fiddling with the cigarette lighter socket. It has me puzzled. I also have the instrument panel taken out so that the only gauges that are in there are the speedo and rpm gauge because they cannot be taken off without disassembling the dash pad.

Also my gas gauge tested at 94 ohms of resistance and my temp gauge tested at 43 ohms. (If i tested it correctly) Does this mean they are still functional?? I tested them by pulling the gauges off completely and just hooking up the positive and negative up and switching to the resistance area on our multimeter.

Thanks again. I'm glad to see someone can shed some light on the issue.

Brian.

[2002Z4CSS]

Is there any aftermarket wiring in that car?

[bgtaylor]

Is there any aftermarket wiring in that car?

It has a newer radio that has some different wiring harness'. And a 5 amp glass fuse from the radio lighting/power going into it. I already checked the fuse and its still ok.

[TrickyTransAm]

I wonder if the rheostat in the dimmer to the headlight control is shorting it out. That could be a cheap fix.
Pull off the headlamp/dimmer switch electrical connector and probe the wires with the multimeter and use the jumper wire to isolate the interior lights from the exterior lights. This will also tell you if your switch is bad.

The dimmer switch is most likely made up of a carbon film trace that has varying resistance, which the further you turn the knob, the less resistance...so bright lights. More resistance, dimmer lights. If the foil is all trashed it might be floating around inside the switch and as you turn - touches the sides of the switch case, shorting it out.

The guage dilema may be sending unit related or wiring related - if the guages checked out around that range, they probably are good. Time to check the signals coming to the dash cluster. See Below.

The cigarette lighter is probably just because the coil on the lighter may be all rusted/gunked up causing a direct short. Purchase a replacement cigarette lighter - the socket is probably just fine.

Does anyone on here have the Lighting wiring diagram for a 1985 that they could scan or send me? I'm sure I could tell you the rest if I had the diagram, but I have had No Luck finding one.
The only one I can google is the "AustinFbody" and it requires a password to get into the site.

Here's the Guage Electrical:

[bgtaylor]

I wonder if the rheostat in the dimmer to the headlight control is shorting it out. That could be a cheap fix.



Does anyone on here have the Lighting wiring diagram for a 1985 that they could scan or send me? I'm sure I could tell you the rest if I had the diagram, but I have had No Luck finding one.
The only one I can google is the "AustinFbody" and it requires a password to get into the site.

I do actually believe I have the wiring diagram but its in my big blue book that my dad currently has at work. I will double check hen he and I get out of work. I went to take the light dimmer switch off and I unscrewed the torx heads and couldn't figure out how to get the black end off. I think I need to take out the fuse and twist it left and unscrew it but I'm not sure. Your idea of the foil causing the direct short is very plausible and It sounds like what is exactly going on. Thank you for all the help you have given me so far.

Brian

[2002Z4CSS]

Somewhere in the dash you have a gray wire for the dash lights that is pinched. The headlight switch rheostat is nothing more than a resistor and that is why the fuse does not blow with it cranked all the way down.

[98blackbeauty]

Sound like to much current draw, before I rip into switch disconnect the fuse going to the radio. then try your lights. What size fuse is blowing? A wiring diagram would help try this site, just enter your michigan drivers license # Its free to mich resident. Gives you chiltons moter manual.

https://elibrary.mel.org/validate?ur...ch%3Fdb%3DCHLL

[TrickyTransAm]

I do actually believe I have the wiring diagram but its in my big blue book that my dad currently has at work. I will double check hen he and I get out of work. I went to take the light dimmer switch off and I unscrewed the torx heads and couldn't figure out how to get the black end off. I think I need to take out the fuse and twist it left and unscrew it but I'm not sure. Your idea of the foil causing the direct short is very plausible and It sounds like what is exactly going on. Thank you for all the help you have given me so far.

Chiltons are just horrid - for this old of a car you can hop on e-bay and get the full GM service manual for about $20. I bought an 82 manual for my co-workers car as a birthday present. Same price as a chiltons...but waaayyy more information.

Did you pull the knob out of the switch? It just pulls out, but there should be a release tab on the bottom of the switch.
Once you get the plate off, you should be able to see the switch. It's behind the IP.
Remove the Dash pad, pull the cluster bezel, pull the speaker, and pull the shaft out of the switch. Then you can get to it.

Compare these colors with what you have. (If i'm reading this correctly)

Yellow - Headlight output to high/low beam dimmer switch
White - Dimmer Lamp Fused
Red - Battery Feed
Dark Green - PNL Lamp Fused
Orange - Tail light Feed from fusebox
Brown - Tail Lamp output
Black - Ground

Check each with your multimeter and jump where necessary to power each individually or check for a ground out condition.

[bgtaylor]

Well one day my dad and I were doing some trouble shooting and saw that I had a couple fuses missing, that I thought I hadn't needed because of not having what the fuse was for. Well we put in some fuses and then the instrument panel starting working perfect again. Pretty sad that something so simple was the issue. I don't know why the instrument panel would be wired to more than one fuse. but oh well. It was still a learning experience. Thanks to all who have given great insight into this issue. Hopefully I won't need to post anymore issues about the car for a while.