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A typical Ford problem


Bossranger

Member
Joined
Oct 5, 2016
Messages
10
City
Central west Michigan
Vehicle Year
1988
Transmission
Automatic
I have finally had it with my NON-working "ALT" gauge. my other 2 trucks did not have a working one. I don`t think I`ve seen a working one in ?? years. Anybodyknow a fix? Withoput installing an underdash unit??:pissedoff:
 
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Please elaborate on "non-working".

I've never had one not work.
 
Yes, me either.

1988 could have an AMP gauge or a volt gauge

AMP meters were mostly used with Generation 1 alternators with external voltage regulators
Gen 2 and up used internal voltage regulators and a Volt gauge in the dash.
The volt gauge just hooks to any Key on 12volt wire in the cab and a ground, so not much to it.

An AMP meter has two parts, the amp gauge in the dash and then an AMP Shunt, in the engine bay.
You don't want to run a 90amp wire in and out of the cab, lol, just asking for trouble doing that.
So an AMP Shunt is used to pass 99% of the amps from alternators B+ terminal to Battery Positive(starter relay on fender)
The Amp gauge's two wires are hooked on either side of the Shunt, and see 1% of the amps going to battery, the gauge is calibrated for the Shunt used, or some AMP gauges are just + and -

Diagram of AMP Shunt wiring here: http://www.therangerstation.com/tech_library/EDiagrams/files/diagram_charging_1983to1985_1.JPG

AMP or Volt gauge is not "part" of the charging system, meaning if either is bad or disconnected it would not effect charging, they are just monitors of the system.
AMP Shunt is part of the charging system, a big part, a 99% part, lol.
 
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I just pulled the dash harness out of a '88 BII (obviously a 2.9) and with this thread in mind (since my ammeter has never worked) I kept an eye out for this "shunt" thing going to the starter relay.

I only saw this one wire that had anything to do with the dash harness (the one that goes from black to yellow with a resistor in the middle) go to the starter relay. It is in with the blower/A/C wiring and goes thru the firewall more or less as one harness.

IMG_6534_zps473ivuvs.jpg
 

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