1990 e350 460 7.5 liter Instrument Gauges

D

Dffraser

Junior Member
Recently I replaced my turn signal and now my fuel gauge and temperature gauge do not read accurately. The auto electric shop that installed the turn signal said it was my instrument cluster voltage regulator. I replaced it but the problem still persists. Specifically, when I turn on the heater blower the temperature gauge goes up.....when I turn on my headlights it goes up even faster. The gas gauge shows 3/4 full but the tank is 100% full. I ran a ground wire from the IC voltage regulator and the fuel gauge quickly went way beyond the “full” line. The upside is that I know the engine is not overheating. I have read that a faulty engine to chassis ground can cause this problem but I can’t find the ground. I have cleaned the battery to chassis ground on each battery but with no impact on my problem. Does anyone have a picture of the engine to chassis ground(s) or have any suggestions??
 
So all of this began after the turn signal switch was replaced? Was the constant voltage regulator you replaced OEM, aftermarket or off-shore?

To find the ground(s) on a vehicle as late as yours, you will need wiring diagram(s). Along with service manuals (which should give a diagnostic sequence), FORD also released the diagram(s) in a manual and are usually available on E-Bay.
 
If the batteries are grounded to the engine, you need a short cable from the engine to the frame, or body, or both. Make sure all paint or rust is removed where you put the grounds.
 
I'm guessing that during the turn-signal switch replacement a nearby connector or wire connection was accidentally dislodged, causing a grounding problem in the dashboard.
This probably isn't news to you and doesn't help much in isolating where to look.
Temporarily adding another ground wire from the truck's body to the gauge cluster circuitry may help, if you can find an easy place to connect one.
Good luck with it.
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KULTULZ said:
So all of this began after the turn signal switch was replaced? Was the constant voltage regulator you replaced OEM, aftermarket or off-shore?

To find the ground(s) on a vehicle as late as yours, you will need wiring diagram(s). Along with service manuals (which should give a diagnostic sequence), FORD also released the diagram(s) in a manual and are usually available on E-Bay.
Click to expand...
Thanks for taking the time to respond. I had a difficult time finding the instrument cluster voltage regulator. It is definitely not Motorcraft, but I don’t believe it was made in China either. The turn signal was made by Duralast. I bought it from Autozone. If I had realized it was as wire intensive as it is, I would have special ordered the Motorcraft. I regretted buying the Duralast as soon as I saw it. I will look for the manual and wiring diagrams online online. Thanks again. Dan
 
dmsfrr said:
I'm guessing that during the turn-signal switch replacement a nearby connector or wire connection was accidentally dislodged, causing a grounding problem in the dashboard.
This probably isn't news to you and doesn't help much in isolating where to look.
Temporarily adding another ground wire from the truck's body to the gauge cluster circuitry may help, if you can find an easy place to connect one.
Good luck with it.
.
Click to expand...
I didn’t watch the installation of the turn signal but I wish I had. I am not a mechanic nor am I mechanically inclined but I am learning a lot on the fly. I will try a few ground wire scenarios tomorrow and will post the results. If I can’t figure it out myself by this weekend I will take it to a Ford dealership next week.
 
Update: I added two ground connections from the chassis to the motor. In each ground I carefully removed the corrosion to ensure I had clean metal to metal contact. Absolutely no impact on my problem. I connected another ground wire from the cluster to the frame with no effect. Each of my cluster gauges has two contact points. The contact points for my voltage and temperature are around 5.3 volts. For my gas gauge, one contact is 5.4 volts and the other is 2.9 volts, and the needle rises very slowly to the 3/4 full mark on a full tank of gas. I am going to play with the instrument cluster grounding a little more today but will take it to someone for repair on Monday if I am unable to identify the source of my problem. I believe it is in the turn signal as indicated above. Will post the resolution once everything is working. Thanks to each of you for responding. I really appreciate it. Dan
 
Have you tried just disconnecting the turn signal switch to see if the problem is still there? Also you could pop out the fuses one at a time to see if this changes anything. Blown fuses sometimes cause unexpected grounds and irregular routes of power. Just guessing on my part, wiring problems sometimes are simple to repair if you dont overthink them. Good luck.
 
I disconnected the harness to my turn signal (it has 10 wires and another wire for the small light that illuminates the gears). I then connected my original turn signal. No change - i.e. the problem still existed. I then removed one fuse at a time - no impact. The only interesting thing that has occurred is that subsequent to installing two motor-to-chassis ground wires, when I turn on my lights the needle on my gas gauge and voltage gauge move much more quickly to the right and will actually peg to the extreme right of each gauge. When the engine is warm, the temperature gauge will also move to the right but it will not peg to the extreme right of the gauge. I checked each fuse under the driver dash and each one is working. I then pulled the entire fuse box away to inspect the wiring. I noticed that the insulation on one wire was open but not severed. I thought it may be shorting against the metal behind it so I wrapped the wire with some electrical tape and stuck some more tape behind it where it would come close to the metal. No impact. I have an appointment with El Toro RV but their electrical specialist is going on vacation and will not be back until Feb 7th.....geez. Anyway, in the interim I am learning a lot about my Ford RV thanks to everyone’s great feedback.
 
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I wanted to post my resolution. It WAS a ground issue. I am sure the seasoned mechanics will roll their eyes but here’s what happened. I removed the instrument cluster (fifth time) and inspected it carefully. I am unsure whether the harness was securely attached so I disconnected it and reconnected it. I then replaced my aftermarket instrument cluster voltage regulator with my original one. I already added two grounds earlier. When I tighten everything up all of my instruments returned to normal. The curve ball I created for myself is that I had three things going on at the same time......the voltage regulator, the ground wires and the harness. I have cleaned up several other ground wires since this incident so the RV is in pretty good shape from a ground standpoint. Even added some directrix grease to avoid future corrosion issues. Thanks again to everyone.
 
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