9 replies to this topic

[fredrogers]

I have a 1987 GL wagon. I love it!

The entire time I have owned it the only gauges that work are the tach and the speedo. The Oil pressure, temp, volts, and gas gauge just sit lifeless and still.

I have taken the dash off and tried to see if I can find any lose / broken wires, but have not seen any jump out at me.

Could there be a ground missing to my dash? Or a power wire?

I did check the fuses and I could not find any that are blown.

Also, I am not sure if it is related, but the rear defrost dose not work.

The lights on the dash seem to work fine, expect the defrost, but the door indicators and 4wd lights work well.

Any good tips for trouble shooting gauges would be greatly appreciated.

-=fred=-

[Jerry DeMoss]

[quote name='fredrogers']I have a 1987 GL wagon. I love it!

The entire time I have owned it the only gauges that work are the tach and the speedo. The Oil pressure, temp, volts, and gas gauge just sit lifeless and still.

Check sending unit for oil pressure.Temp gauge is prob the same thing.Make sure the temp probe on the engine isn't corroded.Gas gauge is another sending unit problem.It may also just be that the connections need to be cleaned up.Good luck.

[Mark Humble]

One tool you can make to help diagnose gauge problems is to buy two resistors, one 50 ohm and one 80 ohm, 1/4 watt. Connect one lead from each resistor together and attach a 12" black wire to this connection and solder them together. Then solder a red wire to the 50 ohm resistors other lead. Solder a blue wire to the 80 ohm resistor and attach alligator clips to the ends of each wire. To keep the resistors from getting damaged, put them in a short peice of PVC pipe and fill with silicon.

Now you have a gauge tester that can be used on almost anything. To use, connect the black lead to ground and the red to the temp sensor wire and turn on the ignition. The gauge should about 1/3 up the scale. (Note:The Red Wire Is For Temp Only) If no reading, repeat the test at the gauge. This is done to check the wire between the gauge and the sending unit. If still no reading, use a volt meter or test light to check for power to the gauge, if there is power, but no reading, the gauge is bad. The blue wire is used to check pressure and level doing the same as above.

[fredrogers]

Very nice! I will make a stop by radio shack on my way home.

Thank you.


BTW this car has had a donner motor put in it before I bought it, could there be a wiring harness unplugged?

Thanks again.


-=fred=-

[Snowman]

Very nice! I will make a stop by radio shack on my way home.

Thank you.


BTW this car has had a donner motor put in it before I bought it, could there be a wiring harness unplugged?

Thanks again.


-=fred=-

Very possible that the o/p and temp senders were not plugged in again. The wires are yellow and I think like 16 gauge or maybe 14 gauge.

[TomRhere]

Very possible that the o/p and temp senders were not plugged in again. The wires are yellow and I think like 16 gauge or maybe 14 gauge.

Or that they are for warning lights instead of gauges... The sending unit for an oil pressure gauge is rather large. The switch for the oil light is small. That should tell you which set-up the engine has.

On the gas gauge issue, check the connector at the tank for the sending unit. I've found those to be corroded enough to not work. On mine, I just cut the plugs out and spliced the wires together using solder and shrink-wrap.

[Cougar]

Except for the voltage gauge, all the other gauges mentioned have a regulator going to them. I would suspect the problem is with the power getting to the gauges. I think it is a common line that supplies all the power to them. I have a manual at home and can research this further if you need more info.

Nice tip from Mark on the test jig.

[fredrogers]

The oil sender unit is "large" it looks (on my car) kind of like a black mushroom about half the size of my fist.

On the temp, I got out my tester and got about 50 ohms of resistance between ground and the unit. So I think the sender is at least working.


On the gas gauge. Do I access the sender unit from under the back seat? or is it under the car?

Thanks for the help.

-=fred=-

[fredrogers]

Except for the voltage gauge, all the other gauges mentioned have a regulator going to them. I would suspect the problem is with the power getting to the gauges. I think it is a common line that supplies all the power to them. I have a manual at home and can research this further if you need more info.

Nice tip from Mark on the test jig.

That would be great. I thought that the power would just go from the fuse box to the gauges. If there is a common place all the power, then that might cure my car.

Thank you!

-=fred=-

[Cougar]

According to my manual for an '88 model there is a black/white wire feeding power to the gauges from fuse #12. There is a red/yellow wire coming from that end and then becomes b/w at a connector.