The Stovebolt Site Forums The Shop Area The Electrical Bay Lost idiot lights ?

I had my instrument cluster out to replace the speedometer head, all bulbs and while it was out I replaced the ignition lock cylinder. I re-installed the instrument cluster and now the generator and oil pressure idiot lights no longer work. Are they on the same fuse or in some other way related? Any ideas?
Thank you

Is there a ground wire to the cluster?

There wasn't but I added one.

The number one answer is what Carl said, be darn sure that there is a COMPLETE ground path to the battery. Then check for hot at each socket with key on, if hot...check bulbs, if bulb works at a remote test place (battery), it's the ground. If no hot, follow both hot wires thru whatever fuses are in the circuit and check those fuses, maybe they are on the same fuse. No one ever knows what a PO has done, especially wiring. The senders operate on ground also, so motor has to have good ground to Battery and battery to chassis and chassis to frame. All shiny clean ground spots. If you have to, run a wire from bulb socket direct to battery ground terminal, that will cut to the chase in a hurry. My money is on Carl, as usual.
P.S. One of those ice pick testers sure helps running things down.

I am getting more confused. There is power going to both sockets and both bulbs work. There is a Dark Blue wire and a Pink wire going to the Oil pressure light. There is a Brown wire and a Pink wire going to the generator light. If I ground the Dark blue wire to the oil pressure light, the bulb goes on with the ignition turned on but does not go out while running. I thought by giving it a good ground, that would take care of the problem. I also cleaned the ground at the battery and engine block.

What year and model truck are you working on?

These are the correct colors. Pink is hot and is fused. Dark Blue (DBL) for oil pressure goes thru a firewall connector to the sender. The brown for gen goes thru a different firewall connector to the voltage reg "L". They are completely different in operation and are not connected in any way except hot and ground. Concentrate on the oil first, it is the simplest. It will be grounded to the motor to light the light when low press (start up) then open the ground to open the circuit and light will go out. It is sometimes referred to as a switch because it is a normally close pressure switch (sender). So if you have hot to the socket when not running (and pressure has gone down) and switch on, and the bulb is good and you have grounded the wire that you took off the switch/sender terminal and the bulb lights but does not go out after pressure builds, then the sender is bad....or the connection AT the sender is bad/loose/corroded/dirty. Figure that out first.

Success, the generator light was not working because of a bad connector at the firewall. The oil pressure light must never have worked while I have owned it because there was no wire at the back side of the instrument cluster connector. I ran a new wire from that out to the sending unit and now I have both idiot lights working properly. Thanks for the help.