924Board.org

[leadfoot]

Is there any way to tell if a gauge is kaput...
I just got a 2nd hand VDO temp gauge and i'm having trouble with its operation...
12v + supply to gauge and earth connection check out as working,
On the temp gauge between the S terminal and earth gives 180 Ohms,
but I'm getting signal from the sender at around 550 Ohms though, which I would think is a little high, the sender is new too.
The resistance of the sender will count down very slowly but the gauge will never go above 40C although i can peg it full by shorting it to ground.
The gauge is a 120 C range but the sender is a 150 C range is this my issue??
I have also read recently that there is a difference in resistance value for gauges from america than australia, any comments on this?
I would have thought the range made little difference to the gauges operation. Is it possible that I've been given the wrong sender as the reading to earth seems high for the 323 - 18 Ohms quoted on the VDO australia website... part number matches the one I ordered and considering that the it also fits into the thread in the oil pan it's the right part number.
The 120C sender is only 50 Ohms different in its range 287 - 23 and so I would think this would make little if any difference.
Any thoughts on this one....

Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[Smoothie]

The sender and gauge need to be matched for an accurate reading. Even if both the 120C and 150C senders operated in the same range (10-180ohms for US VDO gauge&sender) as shown here -
http://www.egauges.com/vdo_send.asp?Sender=250F_120C&Cart=
http://www.egauges.com/vdo_send.asp?Sender=300F_150C&Cart= , 10ohms from the 150C sender might mean 150C, but would display as 120C if hooked-up to the 120C gauge.

Are you getting the 550 ohms with the sender cold? It should be tested at a temp that's within the rated range of the sensor - so 550ohms cold wouldn't be telling you much.

Of course if your gauge is from America or somewhere other than Australia, that easily accounts for part of the inaccuracy. At 287-23ohms Aus compared to 180-10ohms US - that means an Aus 120C sender puts out 23ohms to display 120C on an Aus 120C gauge, while an American 120C sender puts out 10ohms to display 120C on an American 120C gauge.
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"..it's made in Germany. You know the Germans always make good stuff."


'82 924T, US version, dark green metallic, 5 speed Audi 016G gearbox

[leadfoot]

Yeah that was with the gauge cold but I had the engine warmed up and it counted down but never got within a bulls roar of the quoted range. And the gauge never moved off 40C

I guess it depends on how the gauge is calibrated but the VDO gauge I have puts out 180OHM which makes sense according to all sources I've found, yet the senders (I now have a 120C gauge and tested that) don't seem to correlate to the charts.

I'm going to wait until my 150C gauge arrives so I can test the sender installed. I wonder if they are voltage based readings or current based.
thanks.
Leadfoot
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1981 ROW 924 Turbo -
carbon fiber GT mish mash
LS1 conversion in progress...

[D Hook]

I would be very curious to know the answer. I've got a sender I'd like to install but I really don't know if it's matched to the gauge or not.
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'80 924 n/a SOLD