Here's an interesting problem. Let's see if anyone has any ideas. When I got my 86 the engine was half taken apart so I never got to drive in before. During my rebuild I replaced a lot of parts including all the sending units for the dash gauges. I find it hard to believe that all my gauges are bad. Could this be caused by a worn out IVR?

Fuel - It checks OK, I gounded the wires and it sweeps full scale. However, when the needle points to 1/4 of a tank and I fill it up it only takes about 8gals (16gal tank). So the needle is off by about 1/4 of a tank.

Oil - The machine shop put in a standard pump, not high volume. But the needle points all the way over to the "al" in normal.

Temp - The engine temp is good. But the needle doesn't go past the "o" in normal even sitting in traffic, with the A/C on. on a 97 degree day.

Charge - This one actually seems to be working correctly. When I crank it the needle goes a little bit into charge and then settles back to the center within 5mins. So 3 out of 4 gauges seem to be acting up.

 

The oil/temp/fuel guage are powered via the ivr. The charge guage is not.

 

Ah, very good, the IVR is moving up on the suspect list.

 

What is the IVR?

 

D1AZ-10804-A .. ICVR = Instrument Cluster Voltage Regulator (Motorcraft GR513) / Available from Ford and autoparts stores.

Attaches to printed circuit board, located on the backside of the instrument cluster.

Applications: 1971/86 F100/350 & Bronco / 1971/91 Econoline / Misc 1971/79 FoMoCo Passenger Cars.

 

Instrument (Cluster) Voltage Regulator - A device that drops the voltage (to around 5.1V) to the oil, temp & gas gauges. The ammeter operates independently of those three.

 

I doubt it's the ICVR. They usually go out by all your gauges dying, or wild fluctuation sweeps.

Check your ground wire connection for the sending unit. There is a ground wire behind the dash, just to the right of the radio, screwed into the dash metal and one along the frame. Are you sure it's the right sending unit?

This is normal untill the engine and the oil warms up. What kind of oil did they use? If it's 20w50, it could do that.

This is also concidered normal. The radiator has reserve cooling capacity, and the thermostat controls the temps for a constant temperature untill it fully opens. Mine runs on the "o" with super cooling, and will only get so far as the "R" with temps around or above 102 degrees.

 

When the ICVR begins to fail, the gauges (except the ammeter) do the "hula" as their needles swing wildly back/forth on their own.

 

I remember that wire when I installed the new radio. It's there and screwed in. As far as I know it's the right sending unit. It was exactly like the old dead one and was hard to find. I can test the resistance if someone knows the range.

10w40 regular no synthetic. And it reads like this all the time.

Just seems really low to me. I have 190 degree thermostat and normal daily driving the needle barely touches the N.

Is there somewhere I can check the IVR voltage?

 

I'd remove it and clean the mating surfaces and reattach.

I do not have the resistance values of the Sending unit.

However you can eliminate or confirm the ground wire resistance issue using a ohm meter. Remove the wires from the sending unit, and hook the positive lead to the black ground wire. Hook the other end to the metal frame. You may have to scratch a small spot on the metal frame for proper contact. You should have continuity from the black wire to ground. If you have any resistance, then that's the problem.

Do you have the part number of the sending unit?

This is not really normal for the stock gauge. It should read half way up. and drop at idle on a warm engine. What was the quality of your sending unit replacement? Motorcraft? or other?

This is normal. The factory temp was 195. This factory temp was discontinued and all you can get now is the 190 degree one through Ford.

I'm using a 195 degree thermostat and my gauge reads between the "N" and the "O" normally.

Well, if you have a digital VOM, you can check the voltage pulses coming out. This will not tell you anything though, other than it works. You can also adjust the ICVR. There is a little adjustment on the connector side you can turn them up or down. This will turn all your gauges (except ammeter) up or down though. Oil is reading too high and the rest too low for your taste, will not be fixed by adjustment of the ICVR.

 

Correct; when the ICVR thing wigs out, all 3 of those gauges wig out in harmony.

 

My oil pressure guage sits right before the "H" with a high volume pump and 10W40.

With 10W30 it would read half way on the guage with 5 year old oil and a quart of transmission fluid mixed in it, after warming up.

 

My oil and water temp sending units are BWD lifetime warranty. I've always had good luck with BWD parts.

O'Reillys had the Motorcraft IVR in stock, Thanks for the P/N.

The fuel sending unit was really hard to find. I don't remember who I ordered it from. The original one was completely dead, would not work at all. If anyone knows of a place to get a one I'd appreciate it.

Oh yeah, I'm a computer engineer so troubleshooting electrical stuff is simple to me, I just need to know what to look for.

I'll do some more checking tomorrow night. Thanks guys ya'll are a big help.

 

1986? What model? What engine? For what tank?

 

In my signature, 1986 Flareside, 300cid, the side mount 16gal tank.