OK let me state up front that auto-electrical is my least favourite parts of hot rodding and the one I struggle with the most. I'm way out of my depth. Issue: 61 Buick Lesabre COLD and HOT temp lights not working. What have I done. Grounded both wires using ground wire onto block, no lights I've also used a DMM to check voltage at various points along the wires journey and I get only 20-50 millivolts I pulled the dash and I tried grounding the wires from the dash circuit board bulkhead...no lights. All other dash lights work fine the Yellow with black stripe wire goes to the ignition switch, but from what I can tell it's just a ground wire. Either way, I tried grounding that wire also and it show 13 millivolts and no light Clearly there isn't voltage on this circuit It's the YBS and DGWS wires. I've colour coded in green (COLD) and red (HOT) here. How can I get these working? Right now I am thinking 1. the circuit board must be broken, as it's the only way I can see they both get 12V as a source, I cannot see any other 12V source for them. 2. I am thinking of just wiring in an external ignition switched 12 v source into the circuit to get them running. Thoughts ?
Yes. The lights get 12v from the wiring at fuse block to the circuit board, and the "ground" is accomplished when the switches close. The blue "COLD" is "closed" when cold, and "open" when warm and the light goes out. The "HOT" is "open" when the coolant temp is not in the danger zone, and "closes" if it is too hot, and the light comes on. Both lights get momentary "ground" and are "ON" when the key is turned to start the car via a ground contact in the ignition switch (and a similar momentary ground contact for "press accelerator to start" cars)
Thanks...so every other light in the dash works, but HOT/COLD don't. No 12v on those circuits anywhere. Panel fuse is good and checked multiple times. So dash circuit board is getting 12v (as other lights work), but these 2 wires don't.
Yeah but I can't figure out where. Wiring diagram suggests the "connector" that connects to the dash circuit board, as there is no other 12v source on those wires. I'm thinking I might just splice a 12v source into them (switched of course). That said when I turn the key they do momentarily light up as they ground through the key...dimly, very dimly. But that must be the small millivolts they are seeing
The pins on the board often break loose and have high resistance or open condition. They are a small copper tube with three "petals" the are bent/pressed to make contact with the traces on the circular area of the board. If it were me, I would pull the cluster and inspect the printed circuit board. I have repaired the pins on a '64 board with solder, and also repaired damaged traces with jumper wires soldered to good parts of the trace. It takes some patience and little skill, but it can be done. Since the lights need good solid ground to complete the circuits, (almost all problems are ground or connections, not so much a supply of voltage to the accessory being powered) focusing on connections and grounds usually reveals the problem.
The original lights worked via a ground from the temp. switch. When the key is in the on position the green light should come on when cold. While your cranking the engine over with the key the red light will come on. I believe the green light will go out while cranking. This will let you know the bulb is good & the circuit is working properly. The ignition key being in the acc. position lets the amp. light glow dimly. Anything other than this & more complex I will have to dig out my wiring diaghram book. I'll get back to you. Tom T.
No HOT or COLD lights when cranking. I'm almost certain now after tracing all the wires it must be at the circuit board. Can't pull it today may have to wait till the weekend.
