85 F150 oscillating dash gauges
filed in 1985 supra
Question: I need the electrical schematics for a 1985 Ford F150 4×4 with 300 6 cylinder. Anyone know where I can find them?
I have a 85 F150 with 120,000 miles on it and it has been running great these past 17 or so years. For the past 10 or more years, the gauges (temp, fuel, and oil) have given false reading (less gas than there was or very high water/oil pressure when all was normal etc). In the past week their misbehavior has become more of nuisance. At high velocity — for the truck anyway — around 60 MPH, the oil gauge and water temperature like to drop towards 0 psi and C respectively. At other times the gauges simply oscillate at a tenth or hundredth of a Hertz.
So, this weekend I tore the dash apart and started probing around. What I learned was, I need the schematics for the truck and my Chilton’s does not have them. Anyone know where I can get them?
Before too many splinter threads start, I do not think the oil pressure is failing. 1) I have driven around 500 miles or more with 0 psi oil. 2) The water temperature remains low and if I look at the overflow reservoir, it is not full or close. 3) Oil pressure returns when I slow down. Not likely to happen if the pump diaphragm really broke. 4) The truck does not require more gas to overcome the internal welding that would be taking place with no oil.
Thanks in advance for any and all help.
Answer: I have a question about those little metal boxes that they call “voltage regulators”. What sysmtoms do they produce when they go bad? From my experience responses to your thread is good, it draws attention to the original post. I don’t know how much they cost new, I got mine from a wrecking yard and they just give them to me. There’s at least a couple different types of connections other than that they all look alike (Ford I mean). While you’re at it, get yourself a fan speed switch too. 
They won’t charge you for that either. 
I’ve seen similar behaviour on my ‘86, which eventualy turned into slow wipers and dim headlights also. I added a new ground circuit for the headlights, and removed the in-line ground connector near the battery and spliced the the wire together properly. Not only does the connector corrode, but the wire itself corrodes for a fair bit into the insulation.
After all of this I’ve had no more problems.
Want to give your own answer? Want to comment?