volt meter adjustment on Ford F150 1991

55 50 Ron · Jan 29, 2016

Is there an adjustment to calibrate the voltmeter on my Ford truck 1991 F150.

Measuring voltage (with quality Fluke meter) right at the battery terminals gives me 14 volts. Center point of the dash voltmeter is 13
volts and the voltmeter pointer reads below that at about 11.5 to 12 volts.

Thanks Ron

Janicholson · Jan 29, 2016

I don't think there is. I would make sure the voltage at the meter was at the same as the battery, before replacing it. Or understand what the meter really is indicating. Jim

dr sportster · Jan 29, 2016

I would ignore this problem and work on more important stuff.

MARK ROBKE · Jan 29, 2016

Does this dash have the voltage regulator on the back?It looks like a stud terminal circuit breaker,and bolts to the printed circuit,as I recall.Your oil psi,and coolant temp readings would also be low if the regulator is bad.Or ,you may have a bad ground circuit to the dash.Mark

John_PA · Jan 29, 2016

(quoted from post at 23:41:08 01/29/16) Does this dash have the voltage regulator on the back?It looks like a stud terminal circuit breaker,and bolts to the printed circuit,as I recall.Your oil psi,and coolant temp readings would also be low if the regulator is bad.Or ,you may have a bad ground circuit to the dash.Mark

I think you mean a voltage stabilizer. I don't remember if it does or not.

Dalex · Jan 29, 2016

Long ago , I had a '65 T-Bird that had an adjustment on the back of the Voltage stabilizer. Worth taking a look at it .

Janicholson · Jan 29, 2016

When I worked for Ford they were regulators called IVR Instrument Voltage Regulator. But research the issue. Jim

Dell (WA) · Jan 30, 2016

Ron.......you expect a 20% dash volt meter to read the same as a 1% Fluke??? funny man. .......Dell, retired FCC 1st Class licensed electronics calibration engr

Bob · Jan 30, 2016

IMHO, the IVR's were basically "pulsers"/50% duty-cycle controllers that fed the thermally-operated oil and fuel gauges, NOT ammeters or voltmeters.

Anonymous-0 · Jan 30, 2016

(quoted from post at 08:39:02 01/30/16) IMHO, the IVR's were basically "pulsers"/50% duty-cycle controllers that fed the thermally-operated oil and fuel gauges, NOT ammeters or voltmeters.

You are right.

55 50 Ron · Jan 30, 2016

No I don't expect that! That's why I asked if it has an adjustment. And I'm a retired electronics engineer too so I totally understand tolerances, calibration, etc.

55 50 Ron · Jan 30, 2016

So the oil gauge is thermally operated instead of pressure operated?? Oil gauge reads within a few seconds of engine starting and oil wouldn't warm that fast.

55 50 Ron · Jan 30, 2016

Now that's an approach I wouldn' have thought of but it's probably what I'll do.

Anonymous-0 · Jan 30, 2016

(quoted from post at 19:55:12 01/30/16) So the oil gauge is thermally operated instead of pressure operated?? Oil gauge reads within a few seconds of engine starting and oil wouldn't warm that fast.

No, the IVR is thermally operated. A bimetalic strip provides a circuit, it gets hot, breaks the circuit, cools down, makes the circuit again.

The oil temperature has nothing to do with the gauge moving.

Now I can't say if your truck uses an IVR, I know they were used for many years in Ford and Chrysler products but with the advent of computer controlled everything, who knows.

sotxbill · Jan 30, 2016

Very often the voltage at the gauge is NOT the voltage at the battery where the alternator is hooked to. So the gauge is down stream, and measuring voltage at the cluster and this voltage is usually lower due to small wires and bulbs and other loads on it. Some times even have a foil circuit board on the back of the cluster that can have coorsion on it and on its connections. Cleaning all the connections will usually fix the problem. Remember the alternator has a voltage sense lead and it bring that point up to 14.2... turning an the headlights, heater, a/c could in fact bring other parts the wiring system down in voltage pending again on wire size, relay contacts and other factors. Dodge pickups have problems with a ground under the battery tray cause the over drive to hunt due to a .5 volt drop.. .enough to screw up the computer control.

But.. if it aint affecting the driving part, it probably aint worth chasing.

Bob · Jan 31, 2016

Older Fords (and others)used a gauge that had a thermal element/bimetal strip that was heated by a coil of Nichrome wire and tugged the pointer along with it based upon the resistance of the oil pressure or temperature sending unit at the moment, while GM used an electromagnetic gauge.

Nowadays, typically "gauges" are simply a pointer driven by a "stepper motor" controlled by the powertrain 'puter. (When all goes as intended!)

volt meter adjustment on Ford F150 1991

55 50 Ron

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dr sportster

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55 50 Ron

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