Earlier, I posted regarding erratic readings from our temperature gauge. this morning, I believe I determined the problem is some electrical component such as the wiring, the sensor, or the gauge--it was 16 degrees F this morning, and when I started the car (after it had been sitting for about 8 hours), the temp gauge showed a reading in the top 1/3 INSTANTLY. So, we'll start exploring electrical from the simple to the complex. . . .

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83 240 GL

Hey Kurt,

Sorry it took so long to reply to my original post but I was mistaken. The 86-93 cars were the only ones with the temp. comp. board. Your 83 would not have it at all. Sorry for the mistake but I must of gotten my wires crossed somewhere.

I would check the coolant temp sensor in the head to make sure that the wire is plugged in and does not have a short in it. The coolant temp sensor can fail after a long time but I hear it is really hard to get to.

If your able to find it you can unplug the wire from the coolant temp sensor and see what the temp needle does (make sure the ignition is on with the engine off). The temp needle will either go all the way to the top or to the bottom. Once the needle moves ground that wire to the engine and the needle should go to the opposite side of the gauge. If this happens then you can be sure that the wire going to the temp sensor and the temp gauge in the instrument cluster is working okay and that the problem lies in the coolant temp sensor. If the needle does not move to the very top or bottom of the guage then the wiring or guage itself could be the problem but I would suspect bad wiring over a bad guage. Sorry for the confusion and Good Luck!

Sincerely,
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Julio Meza

1979 264GL B27F 127K --> BW55->M46, CLS, IPD Sway, 81+ Dash, Gauges, Flat Hood & E-Codes

1979 262C B27F 163K --> Restoration Project

1984 245DL 216K --> Sport Wagon

2002 Mercedes C320S 33K --> Wifemobile

Sounds like a bad Temperature Compensating Board inside the instrument cluster. This device was placed on US version 200's after 81 to help keep the temperature needle in the middle of the gauge (9'O Clock Position) at all times thus not scaring drives with slight spikes in temperature when the are driving up big hills or stuck in bumper to bumper traffic. When this Temp. Comp. Board fails it causes all sorts of false readings (usually it goes sky high into the read zone in minutes). Best thing to do is to BYPASS this board by taking it out of the instrument cluster and placing a small jumper wire in its place. Check the archive for the Temperature Compensating Board Bypass for a listing with full details and pictures on this easy fix. Once you do the bypass the temperature gauge will work perfectly showing you the acurate reading of the coolant temperature, like a true gauge should. Keep Us Posted & Good Luck!

Sincerely,
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Julio Meza

1979 264GL B27F 127K --> BW55->M46, CLS, IPD Sway, 81+ Dash, Gauges, Flat Hood & E-Codes

1979 262C B27F 163K --> Restoration Project

1984 245DL 216K --> Sport Wagon

2002 Mercedes C320S 33K --> Wifemobile

1983 cars definiely do NOT have the Compensation Board! You'll have to look for another diagnosis, or else the guy picked the wrong year designation and really has a '93.

I agree, bad temp. compensation board, Didn't know that 83's had them. Learn something new everyday...

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90 244DL about 1/4 million miles - original engine/drivetrain :)

Dear JWalker,

Below is a copy of the post I sent to VolvoKurt regarding my incorrect information on the temp. comp. board. Thanks for your time.

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Hey Kurt,

Sorry it took so long to reply to my original post but I was mistaken. The 86-93 cars were the only ones with the temp. comp. board. Your 83 would not have it at all. Sorry for the mistake but I must of gotten my wires crossed somewhere.

I would check the coolant temp sensor in the head to make sure that the wire is plugged in and does not have a short in it. The coolant temp sensor can fail after a long time but I hear it is really hard to get to.

If your able to find it you can unplug the wire from the coolant temp sensor and see what the temp needle does (make sure the ignition is on with the engine off). The temp needle will either go all the way to the top or to the bottom. Once the needle moves ground that wire to the engine and the needle should go to the opposite side of the gauge. If this happens then you can be sure that the wire going to the temp sensor and the temp gauge in the instrument cluster is working okay and that the problem lies in the coolant temp sensor. If the needle does not move to the very top or bottom of the guage then the wiring or guage itself could be the problem but I would suspect bad wiring over a bad guage. Sorry for the confusion and Good Luck!

Sincerely,
-----------------------------------------------------------------------------------
--
Julio Meza

1979 264GL B27F 127K --> BW55->M46, CLS, IPD Sway, 81+ Dash, Gauges, Flat Hood & E-Codes

1979 262C B27F 163K --> Restoration Project

1984 245DL 216K --> Sport Wagon

2002 Mercedes C320S 33K --> Wifemobile