940 fuel and coolant gauge issues-already repaired before?

[ukvolvo]

The hpt we are picking up tomorow has a faulty gauge. Fault is all the way to top and occasional drop to 0 with light. The car had a new board fitted by volvo in the past so is there any areas to check instead of clock?


Really not keen on the idea of a failed fuel gauge

Thanks
Mick

[Forrest]

If the low fuel light is coming on when it drops to zero that suggests the fault is more likely to be with the wiring or in-tank sender than the actual gauge or PCB. The latter faults tend to result in the gauge dropping to zero without the low fuel light.

It would be worth finding the four-wire multi-plug in the rear cubbyhole and experimenting with jumpering the thinner two wires. I expect someone will tell you the rating of resistor you need to use to do this safely and get a particular reading on the gauge. I just go for shorted = full and open circuit = empty.

A similar approach will enable you to test the temperature gauge. The sender is the easier (front) of the two to reach under the inlet manifold. Again, open circuit = stone cold and shorted = off the scale. Use an appropriate resistor to get a mid-scale reading and avoid the risk of damage to the gauge.

[ukvolvo]

Originally Posted by Forrest

If the low fuel light is coming on when it drops to zero that suggests the fault is more likely to be with the wiring or in-tank sender than the actual gauge or PCB. The latter faults tend to result in the gauge dropping to zero without the low fuel light.

It would be worth finding the four-wire multi-plug in the rear cubbyhole and experimenting with jumpering the thinner two wires. I expect someone will tell you the rating of resistor you need to use to do this safely and get a particular reading on the gauge. I just go for shorted = full and open circuit = empty.

A similar approach will enable you to test the temperature gauge. The sender is the easier (front) of the two to reach under the inlet manifold. Again, open circuit = stone cold and shorted = off the scale. Use an appropriate resistor to get a mid-scale reading and avoid the risk of damage to the gauge.

I will have a look thanks, any tips for sender unit? what to expect etc or failure points?

[J liddy]

Wish someone coud sort this problem out there's seems to be a few different fixes even banging the dashboard is suggested my fuel gauge got fixed by soildering but temperature gauge not worked for years even after trying a third dash panel ..is it the connector block on wiring harness if so there's 3 blocks with a lot of pins so which one is is it that gives it the supply I've changed the gauge too .I now have my resivor connected to the low washerfluid so at least that comes on when the coolant resivor is low but I would like coolant gauge to work

[ukvolvo]

Does the obd2 port offer much functionality on 940s? There is always the option of a odb2 temperature gauge if the data is there? Good short term fix

[griston64]

Originally Posted by ukvolvo

Does the obd2 port offer much functionality on 940s? There is always the option of a odb2 temperature gauge if the data is there? Good short term fix

It's not actually OB2