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possible short

Printed From: West Coast Fieros
Category: Technical Topics Forum
Forum Name: Technical Questions and Discussions
Forum Description: Got a technical question about your fiero? ask it here.
URL: http://www.westcoastfieros.com/forum/forum_posts.asp?TID=2661
Printed Date: 23 November 2024 at 9:51am
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Topic: possible short

Posted By: Mumbles
Subject: possible short
Date Posted: 30 August 2011 at 7:12pm

Hello all, i've got a bit of an odd problem, i think it may be an electrical short but im not sure. I was driving yesterday and mid drive i noticed my engine stumbling, radio cutting out and gauges jumping

It took me a min to figure out it was whenever i stepped on the brake, also the (amp meter?) was reading almost to the far right side all the time and would drop when braking.

I stopped and checked the fuses, they seemed fine, but the problem continued then suddenly mid drive it went away. i'm going to try get a gauge so i can check them properly

but besides that any ideas on something else i could check? or should i wait for it to recur?

Car is an 88 Formula

Thanks guys!!

Replies:

Posted By: Dawg
Date Posted: 30 August 2011 at 10:56pm

Hey mumbles, welcome to the group.

When you step on the brake pedal, a fair amount of current goes to the tail lights. I suspect you have a very bad connection somewhere that heats up too much when you apply the brakes. This "eats up" all the voltage going to the devices that are effected.

Somewhere you have a corroded power connection. Look at the wiring diagram for a power path that supplies the items you listed. Then look for a bad connection.

Don't forget to check the ground connections too if the positive side is all good.

Cheers,

Dawg

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You dream it up....I'll make it

Posted By: CFoss
Date Posted: 31 August 2011 at 2:44pm

Mine acted this way when I lost the field connection to my altenator.

What happens is that when a load is applied, the altenator cannot produce more energy and then there is a downward spike in voltage which messes everything up including the ignition system.

Look at the small wires going to the alt for condition. They connect to the field.

You could try:

Get a helper; connect a voltmeter across the battery, rev to 2krpm and hold, then get the helper to step on the brake. Notice a decent drop in the voltage (1 or more volts)?

Also, the same thing can happen if the alt belt is really loose.

Chay

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86 SE 3.4

Posted By: Capt Fiero
Date Posted: 31 August 2011 at 7:59pm

Check the Positive cable that goes from the battery to the starter, on occasion it will rub around the battery box, or on the rear manifold. In the beginning it will just barley arc depending on engine load and how far the engine is leaning over from torque. It will be just enough to cause the alternator to spike when it recovers or drop really low when it arc's. Its a 2 second thing to check, so I usually start with that, then work my way into the harder tests.

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Capt Fiero
88 Fiero GT 5spd V6
Eight Fifty Seven GT V8 5spd.

Posted By: Mumbles
Date Posted: 31 August 2011 at 8:15pm

Thanks for all the suggestions guys, I'll start trying to rule things out
tomorrow :)

Posted By: Mumbles
Date Posted: 08 September 2011 at 11:05pm

Capt Fiero was right on the money!! Thanks again for all the suggestions guys.

Posted By: Capt Fiero
Date Posted: 09 September 2011 at 4:39am

Glad to have helped out.

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Capt Fiero
88 Fiero GT 5spd V6
Eight Fifty Seven GT V8 5spd.