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'73 2002 Electrical Issues???


jd_sims6

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Hi,

 

Two Questions:

 

1.    I've noticed that the temperature gage goes up and down and sometimes into the high zone (in red or close to it), but it seems to be affected by changes in electrical current; like turning on the head lights, blinkers, AC unit, etc.  My son and I recently replaced all radiator hoses and added clean antifreeze.Hoses are not leaking and coolant level is up to filler neck.  In fact, the temp gage can change up or down significantly without much warning.  The engine doesn't seem to be running hot, but how can I tell?  Could this be a grounding issue?  Could it be the thermostat going bad and would "turning on the headlights" cause these temp swings?

 

2.  The right front yellow running light does not illuminate, though the blinker works.  I've replaced the bulb and the blinker works, but not the marker when the headlights are on.  The wires look good and the unit itself seems fine.  Could this also be a grounding issue?  How best to test and troubleshoot?

 

thanks in advance, John & Billy

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Flickering temperature gauge--common problem due to a poor ground between the temp and gas gauges and the body.  Check archives for lotsa posts on the subject.  easy fix.

 

Didja check the appropriate fuse for the front parking light?  IIRC the front parking lights are fused separately on a '73, as with the ignition off you can use the turn signal lever to illuminate either the left or right parking and tail light by themselves.  This is required for on-street parking in many European countries, and some US spec cars have the feature functioning (my 73 does).  Remove the fuse, inspect/clean it or replace it.

 

If the fuse is good, then check to see if you have +12 volts at the wire that feeds the right front parking light.  If not, you'll have to trace the wire back to the fuse.

 

Happy troubleshooting

mike

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Add the additional ground to the gauges for good measure, a bad ground can cause the gauge to malfunction but not normally the way you describe, normally the gauge reads low or dips since yours reads high I would try replacing the temp sender, they are pretty cheap.  If you have access to a laser thermometer check the temp around the sender and see if it fluctuates, it could still be a problem with the cooling system (weirder things have happened), I used to have an old Ford Bronco that I rebuilt the engine on and the machine shop pushed one of the freeze plugs into the water jacket and left it there, it must have been wedged in there because I somehow missed it when I built the engine, that freeze plug migrated around and would restrict water flow randomly and the engine would get hot, I had to tear the engine apart to find the culprit, needless to say I never used that machine shop again.

 

Also check the wire to the sender, if it grounds to the body or engine someplace it will cause the gauge to spike.

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Thanks to you both.  I'll improve the ground and check the voltage.

 

Apparently, the overheating is not only electrical but an actual cooling problem.  The engine over heated twice today driving into DC.  Antifreeze started to come out of the top of the radiator cap and I have to pull over, let cool and add water.  Now wondering if I somehow affected the thermostat when changing the hoses?

 

John

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Since it appears that the temp gauge fluctuations are really fluctuations in the coolant temperature, do checks per previous posts.  I've seen (and had) bad thermostats right out of the box, so testing it in a pan of water is a good idea.  Just suspend the 'stat from some string rather than placing it in the bottom of the pan, as that will give a false opening reading--the metal pan will conduct heat directly to the 'stat body and heat it faster than the water, causing it to open sooner than its rating. 

 

It's very easy to trap air in the cooling system when changing thermostats, so make sure all the air is out of the system--air near the 'stat will keep it from opening.

 

Finally, old 'stats can stick and not open when they're supposed to, then suddenly open.  Symptoms are the gauge quickly climbing to nearly the red zone shortly after driving away from cold, then suddenly dropping to normal or below.  A little water pump lube will help that, although a new thermostat shouldn't stick like that unless it's defective. 

 

cheers

mike

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