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Electrical issue, help/guidance sought


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So my son went to borrow my ‘76 2002 that turned out to need a jumpstart. He manage to hook up the jumper cables incorrectly in the dark by having the positive and negative switched on one of the cars. He said there was a big spark but he thought that was normal. The end result was the car did not start and when I jumped it correctly the next day it ran poorly and there was no electricity getting to the gauges, turn signal, radio etc. I checked the fuses which all looked intact. I have put a new battery in the car and now I believe I need to systematically go through electrical components to figure out what is been damaged. Are there any suggestions as to the proper sequence in checking out the electrical system in my car and what in particular I should check? Of course I’m gonna make my son help 😉 Thank you for any guidance/suggestions
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The first thing to check--after making sure the fuses are all OK--is the alternator and voltage regulator.  They may well be fried.  Then once you have that system checked out/repaired, then check anything with electronics--radio, turn signal flasher, wash/wipe relay etc to see if they work properly, or not.  You'll need a multimeter to check both for voltage in each circuit, but also continuity (ohms).  

 

Most radios have an internal fuse, so if you're lucky, that blew before the radio's circuitry could be damaged.  Let us know whatcha find.

 

mike

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I agree with Mike that the alternator circuity is about the only think I'd really be worried about, as just about everything else is fuse protected, and obviously if you ran it later the starter must still be OK and seems like the coil is as well, although that one is probably worth a check for correct winding resistances.  Likely killed the 'donor' battery that was used also, though!  And have the talk that 'big sparks' /=/ normal!

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Start with the basics to get the car running. 

Check the ignition/starting circuit first. I would disconnect the black wires to the speed relay and the tach. If these are grounded (by damage) the spark plugs will not fire.

Also check for +12V at the idle cutoff solenoid on the carb when the ignition is on.

If all these wires are intact, at lease the car will start. Then you can trace other electrical things that may have been fried.

John

 

PS: mhoffperson....is your car the '76 Mintgrun in San Mateo, CA ???   Is your son Mike???

 

Ignition Circuit.jpg

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I'm trying to think what can't handle reverse voltage on a 2002.

 

As everyone says, alternator for sure, and voltage regulator likely if remote.

 

Wiper relay possibly.

 

Radio maybe, if it's older.

 

Ignitor you if have fitted one (points don't care, do they, Tom?)

 

Voltmeter maybe,

fuel gauge maybe.

Tach, quite possibly.

 

Light bulbs don't care, motors don't care, solenoids don't care...

 

what am I missing?

 

t

 

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52 minutes ago, TobyB said:

what am I missing?

Gauges--especially the tach, which has a little bit of electronic circuitry that may not take kindly to reversed polarity.

 

The easy check is to disconnect the tach and start the engine.  Then reconnect the tach.  If the engine quit, then the tach is probably toast.

 

mike

 

 

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Thank you all. I guess I have some sluething to do.

 

In the interest of full disclosure it was actually my son-in-law that was responsible and he's blaming it on the friend that was helping him😏 

 

P.S. Yes John, you have the right guy. I promptly lost your number the other day (I'm blaming my phone) but I will get ahold of you using alternate means.

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