Ok so today I was working on finding out whats wrong with all of my gauges in my 75 250. my dash lights work just fine along with my fuel gauge but none of the other 3 gauges work. All the gauges themselves are good electrically and so is the laminated mat that everything conducts through. so i guess my question is there's a little metal idk possibly a voltage regulator? with 9v battery connections on it that connect to the laminated mat on the gauges...does anyone know what this is and what it does?...oh and while im asking does anyone have a good wiring diagram for these trucks?
Thanks for the conformation I was thinking that's what it might be. Well the regulator has continuity between the positive and negative connectors and the connectors to the case. The ohm reading from connector to connector is .7 ohms but from each of the connectors to the case its 64.4 ohms...I was thinking this seemed a bit high but from + to case and - to case are both 64.4 ohms so its consistent but i have no specs to compare to.
Quote:
Originally Posted by Jermafenser
Confirmed.
Use a test light to see if it pulses. Also, use an analog meter to see if it pulses 5v.
If the regulator is not the problem then the problem probably lies in the sensors themselves or the wiring...I hope not the wiring but well see. thanks again rick and chad
Ohming out the regulator doesn't tell you anything. It's a non-linear device; I think it might even be electromechanical. Do what you were told; measure the output voltage as that's the figure of merit.
The Fuel Gauge also goes through the Instrument voltage regulator, (IVR) so if the fuel gauge is working correctly, it's not the IVR.
And just some additional information. the ammeter does not go through the IVR, it's protected from extreme voltages and amps from the shunt in the altenator wiring harness.
I have most of the Ford wiring diagrams from 1973-1986, and some from later years. They are huge, and very hard to scan.
[quote=81-F-150-Explorer;7456165]The Fuel Gauge also goes through the Instrument voltage regulator, (IVR) so if the fuel gauge is working correctly, it's not the IVR.
And just some additional information. the ammeter does not go through the IVR, it's protected from extreme voltages and amps from the shunt in the altenator wiring harness.
I have most of the Ford wiring diagrams from 1973-1986, and some from later years. They are huge, and very hard to scan.
yeah after fmc400 mentioned that it was a non linear device i caught on to that.
would this be why it ammeter has by far less resistance then the other gauges?
gotcha where would I be able to track one down? Will I have to hunt for a old ford dealership manual or something of the sort?
Non-linear means there's not a consistent relationship between input and output. Especially electromechanical regulators, which physically disconnect the output from the input during the off-cycle. I am curious, why are you measuring the resistance of the gauges? It's not useful information.
The Fuel Gauge also goes through the Instrument voltage regulator, (IVR) so if the fuel gauge is working correctly, it's not the IVR.
And just some additional information. the ammeter does not go through the IVR, it's protected from extreme voltages and amps from the shunt in the altenator wiring harness.
I have most of the Ford wiring diagrams from 1973-1986, and some from later years. They are huge, and very hard to scan.
yeah after fmc400 mentioned that it was a non linear device i caught on to that.
would this be why it ammeter has by far less resistance then the other gauges?
Most likely, but the diagrams do not state it.
Quote:
gotcha where would I be able to track one down? Will I have to hunt for a old ford dealership manual or something of the sort?
I got mine from the dealer, when they were cleaning up their automotive library. I've also gotten a few items on e-bay.
I am curious, why are you measuring the resistance of the gauges? It's not useful information.
Because its wiring and electronics and im still learning..my thoughts were if power goes it its gotta come out and if the meter read OL then there obviously something wrong...im apparently wrong but thats ok that was the point in asking the question.
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1975 & 1977 F Series Truck Wiring Diagrams
