Temperature Gauge Sender

Temperature Gauge Sender

Author
Discussion

Jas howells

Original Poster:

4 posts

41 months

Tuesday 23rd November 2021
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Hi All I have recently acquired my first wedge, a 1987 350i, so I guess I am going to be a regular on here. I am hoping for my first bit of help. The first job on the list, the temperature gauge isn’t working so I want to replace the temp sensor. Can anyone recommend the best place to get parts?
Thanks in advance.

rev-erend

21,570 posts

296 months

Friday 26th November 2021
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There are a few TVR parts suppliers

Just do a Google search, this part will cost about £15
but these suppliers often add expensive postage and vat which bump up the price.

Worth looking at land rover parts suppliers for the classic v8 as the parts are the same and often cheaper .

Rimmer brothers are also useful with nice diagrams.

ElvisWedgeman

2,715 posts

177 months

Saturday 27th November 2021
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Jas howells said:
Hi All I have recently acquired my first wedge, a 1987 350i, so I guess I am going to be a regular on here. I am hoping for my first bit of help. The first job on the list, the temperature gauge isn’t working so I want to replace the temp sensor. Can anyone recommend the best place to get parts?
Thanks in advance.
Have you checked to see if the gauge is working by shorting the wire at the sensor to an earth for an instant. If so you may be able to buy the sender at a good car spares shop and I don’t mean Halfrauds. I mean an established motor factors. Take the old one with you. When you get the sender you may need to calibrate it to the gauge to make sure it reads correctly.

Jas howells

Original Poster:

4 posts

41 months

Wednesday 1st December 2021
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Thanks for the reply gents. I think I jumped the gun a bit, I bought a new sensor from Rimmer Brothers ( very helpful by the way ) I have replaced the sensor today, but gauge still not working. I’m guessing either the wiring or the gauge itself. Any suggestions what to do next? I will be patient this time. Thanks in advance.

ElvisWedgeman

2,715 posts

177 months

Thursday 2nd December 2021
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Jas howells said:
Thanks for the reply gents. I think I jumped the gun a bit, I bought a new sensor from Rimmer Brothers ( very helpful by the way ) I have replaced the sensor today, but gauge still not working. I’m guessing either the wiring or the gauge itself. Any suggestions what to do next? I will be patient this time. Thanks in advance.
Read the first section of my previous reply.

Jas howells

Original Poster:

4 posts

41 months

Thursday 2nd December 2021
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Hi Elvis
Thanks for the reply. Excuse my ignorance but how do you short the wire at the sensor? Connector on or off the sensor? Where to earth ? Is there any connection of the gauge not working to the coolant temp sensor, because another problem I have is overfueling ( seems to run ok, but stinks of fuel through the exhaust and in the engine bay ) which I have read can be caused by a knackered coolant temp sensor?
Thanks again

adam quantrill

11,600 posts

254 months

Friday 3rd December 2021
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Take the wire off the connector, touch it to the engine block, with the ignition on.

Jas howells

Original Poster:

4 posts

41 months

Sunday 5th December 2021
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Thanks Adam
Done that and the needle on the gauge moved to max then back, so the gauge seems fine. The previous owner appears to have fitted an extra connector to the end of the sensor lead for some reason so I suspect an issue with the wiring. I will investigate further.

adam quantrill

11,600 posts

254 months

Monday 6th December 2021
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The wiring will also be OK then. TVR sometimes fitted a 100-220 ohm resistor in series at the sender end to 'calibrate' the gauge better, this can get broken, you can remove it and the gauge will read slightly higher.

BlueWedgy

405 posts

114 months

Monday 6th December 2021
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As the gauge works when the wire Is grounded then the resistor if in place would probably be ok.

It's not impossible for the new sender to be bad.

Place a multi-meter on the center terminal and earth and measure Impedance.

I would measure the impedance of the new sender with the engine cold then run the engine with the meter attached, to see if the Impedance changes, this could also be done with the old sender and very warm water (do not hold the sender as It will get hot), and measuring again cold-warm,

I would expect the resistance to start maybe about 6k (this depends on the type purchased they used to be colour coded by operating temperature), then reduce as the engine warms.

If you have various resister values added one at a time to the sender wire and earth again, this should make the gauge read in various positions.
To me, It really points to the sender not working or the incorrect one perhaps.



Edited by BlueWedgy on Monday 6th December 19:10