I have been restoring a 1986 F-250 4.9L 300cu Straight 6.
In my instrument cluster, the fuel, oil, battery, & temperature gauges won't work. The Indicator lights and light behind the speedometer work & the speedometer works because it is powered via a cable. What would cause the gauges & lights on the back of the instrument cluster not work? I have changed all the fuses in the truck.
WHAT WIRE POWERS THE INSTRUMENT CLUSTER?

I know these 4 wires

1. Blue/Red-----Illumination
2. Black-----Ground Wire
3. Purple/White-----Brake Switches
4. Yellow/White-----Gas Tank Sending Unit
   
   Here's the WIRING HARNESS for the instrument cluster

Wiring Harness

 

Ok from what I have seen posted the battery gauge hardly moves/work so I would not worry about that one.
The other 3, fuel, oil & temperature gauges, all get power thru the IVR (instrument voltage regulator).
If you do a search for IVR you should find some information on checking & replacing it.
I would go right to replacing it.
Dave ----

 

Is this it, on the back of the instrument cluster? PICTURE COPYRIGHT EBAY.

 

Yes, that is the IVR.

Before you rush out to replace it, test it. Use a test light. One of those big shiny metal dots will light the test light continuously, the other will flash about once a second. Note that this component is riveted to the flexible printed wiring harness and trying to remove it will likely destroy these parts. They are not easily available new.

Before you dive into electrical diagnosis, get a wiring diagram. Original Ford EVTM's are best, but even Chilton's, Haynes, or online sources will give you a basic diagram. Don't be without one.

 

Here are the excellent factory diagrams for your 86. 1986 EVTM - ???Gary's Garagemahal

Check where those plugs plug into the cluster, make sure the traces where they make contact with the plugs are good, they like to come loose and get wrinkled there. If you find one loose, I have used super glue to glue it back in place.

Do the rest of your dash lights work(the ones at the heater controls, the lights and wiper switches, etc.)

 

I took the Instrument Voltage Regulator off. I shook it and it sounds like an old light bulb, something in it is broken off and rattling inside it.

It's the voltage regulator, or at least it's one of the problems. I'll get one off a truck at my friend's junkyard.

 

D1AZ-10804-A .. ICVR - Instrument Cluster Voltage Regulator (Motorcraft GR-513) / Obsolete ~ Available NOS & from auto parts stores.

1971/72 F100/750; 1971/86 Bronco; 1971/89 Econoline; 1973/86 F100/880 // Misc. 1971/79 FoMoCo Passenger Cars.

 

 

Does it snap on/off the flex wire sheet like a 9 volt batt.?

I thought there was something on making one but could not remember if it was on here or not. On the AMC site I am on there is a post on making one.
Dave ----

 

A LM7085 IC will do the job. Can be found at Radio Shack for less than $5, iif those still exist near you.

 

Well, that calls for the extreme close up.


Tried prying a bit and this looks to be well fastened.

Perhaps ND can clarify. Does the IVR come with the printed wiring?

 

I believe you mean a 7805.

Also available at Digikey, Mouser, Electrosonic, etc.

Regulating to 5V is not the same as the pulsed regulation of the original IVR. Results may vary.

 

 

In reading this when first posted got me thinking if the wiring I just installed with a tach if it had the IVR on it as I don't remember seeing it.
Dave ----

 

There was talk on another site that the stock IVR changes out put based on the temperature. So as the temp changes inside the car/truck so will the out put and remember the gauges are in this same temperature.
Dave ----