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Series III temperature gauge


Niko Saastamoinen

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These where some readings I got when testing my sender in water , has the engine got a good earth.

Temperature 18 56 100C

series sender 323 118 56 ohms

in that case 76 ohm isn't a very odd reading. I'll try to make sure the connection to the sender is good, and as they don't cost a fortune I'll order a spare with my next shipment

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If there was sealant I wouldn't measure 76ohm to battery negative (or engine as earth)...

now I've red some more... It might be worth mentioning the heater doesn't work.... maybe still themostat open all the time??

will replace the sender anyhow.

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  • 10 months later...

If there was sealant I wouldn't measure 76ohm to battery negative (or engine as earth)...

now I've red some more... It might be worth mentioning the heater doesn't work.... maybe still themostat open all the time??

will replace the sender anyhow.

replaced and working. However... I get the exact same reading as the topic starter... Just below the red HOT. but it stays there.

Probably a 80+ thermostat but I'll see if I can get a good reading on the voltage regulator (if I can find it) and replace it with a LM7810 + 100uF and 10uF capacitators. Sould be 3 minutes of soldering, some hot glue and some tape :)

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An 82 deg thremostat should give a reading right in the middle of the normal range, a 74deg stat about 1/3 of the way up the range. It sounds like you have a mismatch between the gauge and sender unit, either because one is from a different year than the other, or because the sender is a pattern part.

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Turn the ignition on and short the sender wire to earth - the gauge should go to full deflection hot. If it doesn't, you could have a feed problem from the fuse box, a bad voltage stabiliser or a wiring fault. But if the oil pressure gauge is working, then it's likely the wiring or the sender. Gauges do fail, but the senders are more often the problem. On the bright side, they're not hard or extraordinarily expensive to replace.

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Might it just be that cooling a working 109 series III 2.25di on a 36 degrees day uphill just doesn't work?

It even touched red today a few times. Some driving downhill made the temp drop a little again. Enough fluid in there and due to the fact that it does somehow manage to cool back down I assume the thermostat is working. (or is that an dangerous assumption?)

What are the cooling bottlenecks on 109 2.25di? As they are driven in africa they should have a good cooling system right?

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It should be able to cope. I did have problems with my 109 and a 12J engine which new rad and pump didn't solve. It turned out that using the standard 2.25 petrol exhaust on a 2.5 diesel was the cause - as soon as I replaced the exhaust, the high temperatures uphill stopped (borderline of the red on long climbs, which would quickly reduce in third gear). With a 2" exhaust, the needle sat in the middle under all conditions using the standard SIII cooling system. If you are using a 2.25 petrol exhaust on your DI, I'd bet that's the problem. (By DI, I presume you have a de-turboed TDI? That would be 2.5, rather than 2.25)

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hmmmm on working rev's (would guess around 2500rpm) in neutral it ends up staying in the middle and stays there during my full test run. about 20 minutes.

Temp in the radiator seems to be ~66 degrees steady celcius. (cheap chinese meter that would easily do more than 10% off)

Will now have it all cool down and do a full run while metering the radiator as well.

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A std 2.25 diesel (indirect injection) system will cope with working hard in any temp . What temp difference do you have from top to bottom of rad ? and are the cowls in place ?

Checking the temp with a separate gauge is a good plan , you could check the meter by taking a reading on a boiling pan of water ?

cheers

Steveb

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