Another Electrical Issue Temp Gauge Increase When Lights Are On...

vladtepes · Mar 20, 2010

ok.. i think i got my first electrical issue just about all figured out (the pass side window not working)

But i have now encountered another electrical issue...VERY sure its electrical in nature and NOT a real cooling issue..

someone DID at one time replace the alternator... and here is what i know..

91 lx 170k miles

*with the car running lights off driving the temp gauge rises to the second mark within the "normal" area of the gauge...

*with the car running lights ON driving it goes one full mark higher....

*if i shut the car off completely and leave the lights on the needle slowly climbs till it can not climb anymore...

*the second i shut the lights off it stops climbing...

*shut the lights off prior to shutting the car off the needle acts normal..

this car has been a real wiring/electrical headache.. you guys really helped last time .. where do i even start with this one!...

5.0Droptop · Mar 20, 2010

Pull all the gauge cluster out and throw it away then buy a florida50 gauge cluster and replace it all with that. Works very well.

Florida 5.0 - 1987 - 1993 Instrument Clusters

If you do not want to do that. I would take a look at the voltage regulator in the cluster, maybe its going bad. 1990-93 MUSTANG INSTRUMENT VOLTAGE REGULATOR

331strokerlx · Mar 20, 2010

My temp guage does the same exact thing.

vladtepes · Mar 20, 2010

5.0Droptop said:
Pull all the gauge cluster out and throw it away then buy a florida50 gauge cluster and replace it all with that. Works very well.

Florida 5.0 - 1987 - 1993 Instrument Clusters

If you do not want to do that. I would take a look at the voltage regulator in the cluster, maybe its going bad. 1990-93 MUSTANG INSTRUMENT VOLTAGE REGULATOR

I have actually considered that.. and may do that at some point.. but its a pretty hefty price tag... i already have several autometer gauges from my last car that i will at some point integrate into this car.. so that cluster IS a nice option..

331strokerlx said:
My temp guage does the same exact thing.

interesting.. has it always? do you just keep a mental note of what is normal with the lights on or off, and just go by that.... lol

331strokerlx · Mar 20, 2010

It's always done it. I know in my head how much the guage normally goes up with the lights on. It was annoying at first but I'm used to it now.

vladtepes · Mar 20, 2010

331strokerlx said:
It's always done it. I know in my head how much the guage normally goes up with the lights on. It was annoying at first but I'm used to it now.

notice any difference between winter and now that the weather is breaking? pretty sure everything is ok... but it just had me a little worried.. i noticed that over the past few days without the heat blasting its been running a tad warmer.. still nothing above half way though...

TOOLOW91 · Mar 20, 2010

mine did the same thing in my 90 also

331strokerlx · Mar 20, 2010

It stays consistant year round.

LiquidGT · Mar 20, 2010

Mine does (or did) do the exact same thing, the fix is to get an aftermarket gauge.

I tried EVERYTHING to fix it...

- New sending unit
- I checked the ground strap on the firewall
- Cleaned the 10 pins
- I swapped temp/volt part of the gauge pod from a different cluster
- Swapped the voltage regulator (I found out later that its just for the gas gauge)
- I actually soldered a wire to the cluster and grounded it directly to the battery. And I think I soldered a wire to the sending unit to the cluster too.

I used to drive with the crazy temp gauge, but that was part of the reason why my stock engine blew. Sometimes I couldnt tell if the gauge was being stupid or if the car was actually overheating.

FrankenStang · Mar 20, 2010

Interesting username.

Thread moved to Tech.

Cobra1741 · Mar 20, 2010

my temp guage does same thing.. runs at second mark with lights off. lights on it runs in the middle.... but i know im not running hot. just electrical

HISSIN50 · Mar 20, 2010

If not mentioned, check the gauge cluster grounds.

vladtepes · Mar 20, 2010

FrankenStang said:
Interesting username.

Thread moved to Tech.

thanks... lol

HISSIN50 said:
If not mentioned, check the gauge cluster grounds.

yeah i just noticed tonight that the voltmeter jumps around a bit also... gasa is perfect oil is fairly steady as well... speedo jumps around a lot also..

thanks to all for the feedback!

vladtepes · Apr 7, 2010

completely over it.. will NOT be trying to figure it out.. once i get done with some other stuff im just going to replace EVERYTHING with autometer gauges.. id rather run a bunch of independent gauges and be sure they are accurate than dick around with the stock cluster hoping its right..

Repostyle · Apr 7, 2010

vladtepes said:
thanks... lol

yeah i just noticed tonight that the voltmeter jumps around a bit also... gasa is perfect oil is fairly steady as well... speedo jumps around a lot also..

thanks to all for the feedback!

The speedo is a seperate problem, it's mechanical, driven by a cable. That could be a bad cable or broken gear.

foxforce33 · Apr 7, 2010

My '90 did the very same thing with the temp/headlights. I ignored it.

Cobra1741 · Apr 7, 2010

my cobra does the same thing... i jsut watch the temp with the lights off, with them on its not accurate.

vladtepes · Apr 8, 2010

i really think that at some point im going to just go to the florida 5.0 setup.. i already have half the gauges anyway.. and at least that way it will be reliable.. this motor is beat to **** anyway... runs ok doesnt smoke, but has 180k on the clock, and i just noticed a small amount of oil in my coolant reservoir.. so i know unfortunately its only a matter of time.. this car was purchased as a project and that project is probably going to take at least a year to get rolling.. and i see a motor swap out in the not so far future.. it will all come along you know..

BlackGT89 · Apr 8, 2010

I can't add much that hasn't already been mentioned, but my '89 GT used to do that bad, I could turn the heater blower up to high and literally watch the temp gauge blast up at the same time (purely an electrical thing). Of course it also went up with the headlights on as mentioned. I'm not sure when it stopped but it doesn't do it anymore. When I put my 3G Alt on I also added the extra ground wire from the block that was recommended, maybe that helped. Also I also installed a new Griffin aluminum radiator and was able to run my electric fan on high, so maybe between all of those things the gauge just doesn't creep up high enough to agitate problem anymore.

Another Electrical Issue Temp Gauge Increase When Lights Are On...

vladtepes

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5.0Droptop

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