88 electrical problem. Any ideas? (Page 1/1)
Jimbovi JUN 02, 05:35 PM
First of all, thank you all for being here for me to vent to...
That said. I have an 88 Fiero Formula I've owned for about a decade with no serious issues.

I December, I repaced the alternator with a 140a model from summitracing but the weather got bad and then my work got busy so I never tested it.
Today, I put a new battery in and started up the car and my gas gauge is pegged, my temp gauge is below the lowest setting, my battery gauge is at 0 but my oil pressure gauge is pegged.

Since it was the biggest scare for me, I turned off the car and reseated the oil pressure sending unit connector and tried it again. No change.
I turned off the car again and cleaned off the connector and tried it again. This time my gauge fuse blew.

I checked the ground to the alternator, added an additional ground from the battery's grounding point to the block incase I had grounding issues. Fuse still blows.

I unplugged the oil pressure sending unit, temp gauge is responding but its at a lower range than before, the fuel gauge is still pegged, the battery gauge is now working properly and the oil pressure gauge is pegged (because its unplugged). I tried grounding the center terminal on the plug to verify if my sending unit was bad and that blows the gauge fuse.

So my questions for the group:

1) Is the alternator the problem, or was it coincidence that the issues started with a new alternator?
2) Any suggestions on where I should look next?

Again thanks for being here, all.. and I appreciate any ideas.

Jimbovi
Gall757 JUN 02, 06:15 PM
You will need to find the model number of the alternator you purchased. It may be wired differently than the Fiero stock alternator.
Jimbovi JUN 02, 07:41 PM
Powermaster Street Alternators 478021

It came up as compatible with my Fiero on their site.
*shrug*
I just checked and its a CS130 style alternator. Plug on the alternator says SFLP with no wire lead in the P position.
alternator also has the same markings PLFS and the letters all line up when connected.
My assumption is that the alternator is good.

Any other ideas?

--Jimbovi

[This message has been edited by Jimbovi (edited 06-02-2019).]

DavidM JUN 03, 04:54 PM
In every case with alternators, I always measure the battery voltage with a meter as they are running looking for the 13.8-14V.

In this case, it does sound like runaway voltage from the alternator which is very dangerous for just about everything electrical in your car.
Since it is nearly impossible to get a single wire alternator wired in such a way as to produce this (all you have is the big red lead from the battery, the ground to the engine and the field winding (and maybe a panel light connection) - could be the regulator in the alternator is shorted.

Rather than risk your cars electronics, I would suggest taking it to one of the parts places that offers free testing, either that or wire it up separately on your bench and spin it up to test. At idle with a battery, it should put out 13,8-14V

Hope that helps a little. I have a Powermaster on my '86 so I know they work.
Jimbovi JUN 03, 07:26 PM
So I believe it was a coincidence that the gauge fuse started blowing at the same time as the alternator. I just removed the alternator entirely and the moment I turn the ignition switch on, the gauge fuse blows.
The only way it doesn't blow is if I unplug the oil pressure sending unit.

If I ground the center hole on the oil pressure sending unit plug (which should zero my oil pressure meter), the gauge fuse blows.

--Jimbovi
Camel JUN 04, 05:16 PM

quote
Originally posted by Jimbovi:

Today, I put a new battery in and started up the car and my gas gauge is pegged, my temp gauge is below the lowest setting, my battery gauge is at 0 but my oil pressure gauge is pegged.



Check for pinched wires around the battery, and anything possibly not hooked back up properly.