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1980 - 1986 Bullnose F100, F150 & Larger F-Series Trucks Discuss the Early Eighties Bullnose Ford Truck

Speedometer help

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Old Jun 8, 2022 | 03:16 AM
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Speedometer help

I recently bought an 85 f250 and it has some problems with the dash. None of the guages or lights work on the dash. I was told when I bought the truck that the previous engine blew up and it was swapped for a 79 351 out of a bronco. The truck runs, drives, and stops just fine, there is just no interior electrical. I was wondering if anyone knew what I should check or where to look to make sure everything was plugged in and connected right, or if I should rewire everything from scratch. If I should go from scratch any links to videos or wiring diagrams on how to do it would be appreciated also
 
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Old Jun 8, 2022 | 09:37 AM
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The engine swap should not have affected any of the interior lights, unless something got damaged in the process. Unless the installer totally botched the wiring, the gauges should work, too. For example, an oil pressure sending unit should work the same whether it's threaded into a 1979 or 1985 engine.

I'd suggest picking one circuit that isn't working and investigate. With any luck, you will find a common issue that has affected the other circuits, leading to an easy repair.

Here are the wiring diagrams for 1985:

https://www.garysgaragemahal.com/1985-evtm.html

The instrument panel illumination would be a good place to start, as the circuit is fairly simple:



Check fuses #4 and #17 to get going. Then you can check for power reaching the individual bulbs. Make sure the headlight **** is rotated clockwise, as this is a dimmer switch and you'll want full brightness for troubleshooting. The dash lights are not especially bright, so check after dark to see if they work at all.

One little gotcha in that wiring diagram. It shows "Defrost Control Illumination" but that was an extra panel fitted only to Broncos with the optional rear window defrost. You should have all the other stuff, just not that light.

 
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Old Jun 8, 2022 | 12:50 PM
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Originally Posted by kr98664
The engine swap should not have affected any of the interior lights, unless something got damaged in the process. Unless the installer totally botched the wiring, the gauges should work, too. For example, an oil pressure sending unit should work the same whether it's threaded into a 1979 or 1985 engine.

I'd suggest picking one circuit that isn't working and investigate. With any luck, you will find a common issue that has affected the other circuits, leading to an easy repair.

Here are the wiring diagrams for 1985:

https://www.garysgaragemahal.com/1985-evtm.html

The instrument panel illumination would be a good place to start, as the circuit is fairly simple:


thanks man this was exactly what I was looking for
 
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