My first post, so please bear with me while I figure this out. I have an '86 240 DL wagon, manual M46 tranny. I currently have a problem with my instrument cluster that I can't troubleshoot. The gas gauge and temperature gauge and the cluster lightbulb on the right side of the cluster are not working. But they don't work simulaneously. When they work, all 3 items work perfectly, but then when they go out, all 3 of them go out at the same time. They have been working intermittently for the past 2 years, but now they are permanently done. The gas gauge reads super high and the temperature gauge hangs out just below or just into the red. So they are both getting electricity, just too much it appears. The gas gauge and temp gauge are both grounded at their sending units, so it can't be 2 different bad grounds going out simultaneously everytime. Fuses are all good. I have replaced ALL parts of the cooling and temperature systems, including: radiator, coolant, coolant tank cap, temperature sending unit and wiring, radiator hoses, thermostat, temperature compensation board (well actually I just connected the #1 and #3 wires and removed the comp board), etc. I have also removed the cluster and replaced the voltage stabilizer. It worked for less than a week after doing that. I took it apart again and cleaned the contact points and put some dielectric grease in the connections around the voltage stabilizer. Still nothing.

Any ideas? The backside of the cluster is pretty interesting stuff and I can't figure out how electricity is actually conducted around inside it, like is there a conductive surface under the brownish plastice material that covers the backside of the cluster? I'm worried that the cluster itself is actually bad since all the other compenents have been replaced with no success. How can I test the cluster or voltage stabilizer to pin down the problem?

Thanks for the help.

 

See "m" in the attached picture, it shows the pinout of the regulator. Basically it takes battery voltage in and outputs +10VDC for the fuel and temp gauge.

 

Ok, I understand that much. How do I test it? I can't get a voltmeter behind the cluster when all the wires are hooked up. And even if I could, which wires/connections am I testing? There are 3 connections on the stabilizer. Is one for the gas gauge, one for the temp gauge, and 1 go for other items (the bulb)? I've already installed a new voltage stabilizer and it worked for ~a week (P.S. I replaced the alternator and a new voltage regulator last summer, so ~10,000 miles). Why does one of the cluster lights also coincide with these gauges not working? Is there simpy a bad connection somewhere in the cluster right where the stablizer plugs in? Yes the cluster bulb is fine. Seriously, all 3 items work or don't work is perfect unison.

Thanks!

 

The drawing shows the pinout of the regulator. pin 1 - batt, pin 2 -ground, pin 3 - 10VDC. Connect a wire to pin 3 long enough so you can measure it with the cluster installed.

You might see if the turn signals work when the gauges don't, they share fuse 13. Most likely it's a loose connection somewhere, maybe the socket the regulator plugs into (or a broken solder joint).