Temp gauge

[volvo always]

I have a 1996 Volvo 940 LPT Auto.

I went out today and temp gauge was working fine. Went out again later and thought strange the temp gauge wasn't reading, then noticed the needle flickering between nothing to halfway/normal position. Then not reading.

Is this a duff temp sender under the manifold? Seems more electrical rather than thermostat. Thermostat is 4 years old.

James.

[Forrest]

You can test whether it is the instrument/wiring or the sender by removing the connector from the sender and shorting the two wires at the connector with a bent paperclip or similar. Turn the ignition to position II and the gauge should shoot up to maximum.

The gauge sender is the more accessible of the two under the inlet manifold. I found temporarily removing the knock sensor made access easier to remove a faulty one.

[Laird Scooby]

Originally Posted by volvo always

I have a 1996 Volvo 940 LPT Auto.

I went out today and temp gauge was working fine. Went out again later and thought strange the temp gauge wasn't reading, then noticed the needle flickering between nothing to halfway/normal position. Then not reading.

Is this a duff temp sender under the manifold? Seems more electrical rather than thermostat. Thermostat is 4 years old.

James.

Try driving it for about half hour with the heater set to hottest and to the vents, fan full on.

The guage will do one of two things, either settle on its cold stop or start working correctly.

If you try shorting the connectors in the sensor plug, use a 100 Ohm resistor, not a paper clip, much safer for the instrument!

[lynns hubby]

If you haven't already, check your coolant level. The sender wont work if your level is low enough to allow it to sit in an air pocket. If its that low you have problems.

[volvo always]

Went for a 30 minute drive and it rose so far then went back to dead.

Coolant level is midway between low and max.

I'll test hopefully Friday.

Thanks. James

[Laird Scooby]

Originally Posted by volvo always

Went for a 30 minute drive and it rose so far then went back to dead.

Coolant level is midway between low and max.

I'll test hopefully Friday.

Thanks. James

That sounds very much like the guage James or possibly the instrument cluster PCB has dry joints. My fuel guage was the same for the first 3 years of owning my 760 (Yazaki instruments) and i fixed that by servicing the many dry joints i found on the PCB - however i didn't do the ones linked to the illumination circuits and i'm down to one small bulb at the top of the speedo working now so need to pull it out and find out what's going on.

It may be the LEDs have all failed except one but i doubt that somehow, especially as sometimes the others will come back on for a short time then all go out again at the same time.

When i remember the name of my thread on the fuel guage fix i'll link to it, might give you something to look for!

[volvo always]

Originally Posted by Laird Scooby

That sounds very much like the guage James or possibly the instrument cluster PCB has dry joints. My fuel guage was the same for the first 3 years of owning my 760 (Yazaki instruments) and i fixed that by servicing the many dry joints i found on the PCB - however i didn't do the ones linked to the illumination circuits and i'm down to one small bulb at the top of the speedo working now so need to pull it out and find out what's going on.

It may be the LEDs have all failed except one but i doubt that somehow, especially as sometimes the others will come back on for a short time then all go out again at the same time.

When i remember the name of my thread on the fuel guage fix i'll link to it, might give you something to look for!

I'm rather lucky so far as my 1986 740 and current 940 in the 9 years of owning, all the guage's worked until the above! If you find it, that would be great. I have one dash light bulb out as only half the right side of the speedo is dark, just turned up brightness. Fix that while I'm in there!

James

[Laird Scooby]

Originally Posted by volvo always

If you find it, that would be great. I have one dash light bulb out as only half the right side of the speedo is dark, just turned up brightness. Fix that while I'm in there!

James

https://www.volvoforums.org.uk/showthread.php?t=300846

There you are James, the brain cell came good in the end and i remembered!

[Clan]

Originally Posted by volvo always

I have a 1996 Volvo 940 LPT Auto.

I went out today and temp gauge was working fine. Went out again later and thought strange the temp gauge wasn't reading, then noticed the needle flickering between nothing to halfway/normal position. Then not reading.

Is this a duff temp sender under the manifold? Seems more electrical rather than thermostat. Thermostat is 4 years old.

James.

Yes more likely a rotted wire rubbing or the sender itself ..

[volvo always]

Went for a drive today and no gauge working.

Managed to remove securing clip and undo the electrical connection. Take it temp sender is nearest the bulkhead?

Disconnected it and without bridging pins started the car and temp gauge went straight to mid point/reading and engine cooling fan fired up. Noticed connector pins had gone green so cleaned them and re connected.
Started up and now reading correctly. See if it continues from cold.

James.