Odd problem, no key in ignition, turn on headlights and......

1993SSP

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Jul 5, 2010

#1

• Jul 5, 2010

• #1

If there is no key in the ignition and I turn on the headlamps in my 92 coupe the temp guage will rise all the way to the red mark. Anyone ever experienced this??

 

jrichker

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#2

• Jul 5, 2010

• #2

That's a symptom of a bad or missing alternator power ground.

2.) The secondary power ground is between the back of the
intake manifold and the driver's side firewall. It is often missing or
loose. It supplies ground for the alternator, A/C compressor
clutch and other electrical accessories such as the gauges.
Any car that has a 3G or high output current alternator needs
a 4 gauge ground wire running from the block to the chassis
ground where the battery pigtail ground connects.
The 3G has a 130 amp capacity, so you wire the power side
with 4 gauge wire. It stands to reason that the ground side
handles just a much current, so it needs to be 4 gauge too.

The picture shows the common ground point for the battery & extra 3G
alternator ground wire as described above in paragraph 2. A screwdriver
points to the bolt that is the common ground point.
The battery common ground is a 10 gauge pigtail with the computer ground
attached to it.

Picture courtesy timewarped1972

Correct negative battery ground cable.

 

1993SSP

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#3

• Jul 5, 2010

• #3

Thanks for the info, I just got this car and I def know that ground wire is missing because there were new ends installed on the cables. I will dig into it sometime this week and fix it.

 

1993SSP

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Jul 6, 2010

#4

• Jul 6, 2010

• #4

I checked and cleaned all grounds and the guage still does it, any other suggestions??

 

aar0s

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Jul 6, 2010

#5

• Jul 6, 2010

• #5

mine does it also, someone told me once that it was a bad ground somewhere in the dash, but i wouldn't put much stock on that.

 

1993SSP

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#6

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• #6

If I have a bad ground I would love to find it, small things such as that drive me nuts!

 

jrichker

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Jul 7, 2010

#7

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Start the engine and turn on the headlights and A/C blower. Get out your voltmeter and measure the voltage between the engine block and the negative battery post. Change the blower speed from high to low. The voltmeter reading should not change and it should not be higher than. .2 volts. If it is, you still have ground problems.

See Automotive Test Tools for help for help troubleshooting voltage drops across connections and components. .

 

Strype

Cuthbert catcher

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#8

• Jul 7, 2010

• #8

That used to happen to my 86 and never did find out what the problem was.

 

R

rudy herrera

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#9

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i recently install a set of hids in my fox and this seams to happen to my car tooo i hit the lights and the temp goes up i turn them of and it goes down
wat could it be

 

HISSIN50

"How long does it take to get help in here?

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Jul 8, 2010

#10

• Jul 8, 2010

• #10

Pay particular attention to the gauge ground pathway.

 

1993SSP

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Jul 11, 2010

#11

• Jul 11, 2010

• #11

HISSIN50 said:

Pay particular attention to the gauge ground pathway.

Click to expand...

This problem is starting to annoy me! I have cleaned and checked all grounds, even the ground near the computer. Still doing it.

I pulled off the drivers side kick panel, there was a 2 wire plug, one wire is blue with white stripe, other is orange with green stripe. The orange wire is cut, any info on what that is?? Also I checked all wiring near the solenoid and the fusible links. I found one plug that has a black wire and a black with white wire, it is pluggged into nothing and I could not find what it plugs into. There was also another plug in the wiring at the driver kick panel that was unplugged and I could find nothing it plugged into, seems like it had blue and pink wires to it

Where is the ground for the dash harness/guage cluster located?

I hate wiring problems

 

jrichker

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Jul 11, 2010

#12

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See http://www.stangnet.com/tech/cluster87-93.pdf for a diagram of the instrument cluser.

 

jrichker

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#13

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Check out the instrument cluster electrical diagram...

Once you see the temp gauge wiring, you will see that none of the grounds for the instrument cluster are connected to it. The temp gauge sender depends on the engine to body ground. I suggest that you use the voltage drop measurement technique I posted earlier to check the engine to body voltage drop. Then do the same test from the brass temp sender to the battery negative terminal. You may find that the voltage drop between the sender and the battery negative terminal increases as you increase the electrical load.

 

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LiquidGT

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Jul 13, 2010

#14

• Jul 13, 2010

• #14

Mine does it too, I did everything from checking/adding/replacing grounds and swapping the voltmeter/temp gauge part of the cluster. I even ran my own separate ground from the IC board on the temp gauge directly to the battery and a separate signal wire... same thing.

So you need a ground, signal, and 12v switched ignition for the temp gauge to work right. Then how can the temp gauge max out with your keys in your pocket? Where is the 12v ignition coming from???

 

1993SSP

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Jul 14, 2010

#15

• Jul 14, 2010

• #15

Beats the heck out of me, I'm gonna do the voltage drop test this weekend and see how that goes.