Thread: Temperature alarm switch D2 auto

Originally Posted by rjhjstr

Does anyone know the setting for the temperature alarm switch which is built into the trans cooler on a D2 TD5 auto?
Because I tow a heavy caravan, I have fitted a transmission oil cooler at the very front of the radiators so that it gets maximum cooling. The original oil cooler is gone. I also use synthetic auto trans oil (Castrol transmax Z)
However I want to keep the temperature warning light that is fitted into the dash. It's easy enough to build a little electronics box that will monitor the transmission oil temperatue by a sensor strapped to the outside of the steel pipe that exits the ZP4HPEH22 and feeds the new oil cooler. This would trigger the original warning light.
The question is what's the appropraite temperature to trigger the transmission temperature warning light?

Cheers
Russell

It doesn't state the temp in RAVE - but if you have the original sensor, you should be able to test that to find out at what temp it switches (if it's the switch type. Or if it's a thermister, you should be able to measure the resistance of the original at various temps.

Stand the sensor in shallow water in a fry pan, and use a suitable temp probe as well - or a termometer that covers 100 Deg C plus.

Connect a meter, measuring resistance (ohms) to the two wires/plug - slowly heat the water.

If it's a direct switching type then the reading will switch from something like OL (depends on type of meter) to a near zero resistance.

Slowly heat the water watch the meter and the temp - when switching occours read the temp.

If it's a resistance thermister type (sorry not sure what it is) then stand it in the cold water - measure the temp and the resistance, slowly heat the water - and measure the resistance every 10 degrees or so. By the time the water is hot you should have enough reference points to get a matching thermistor.

If I get chance today - I'll try and measure mine - however mine is a V8 - but I would think they would be similar

I hope you have high pressure fittings and a high pressure ATF cooler, as the ZF is an exceptional gearbox that puts up to 115psi through the cooler unlike most other autos that only pass low pressure.

125 deg is getting hot enough for me to want to know about it. Normal operating temp for these driven reasonably hard can be up to 90deg, I would guess oil breakdown begins at about 150, so 125 would be a good start.

JC

I'm not a 100% sure but I'd also check that the temperature sensor doesn't report back to the Gearbox ECU.

Originally Posted by dm_td5

I'm not a 100% sure but I'd also check that the temperature sensor doesn't report back to the Gearbox ECU.

Doesn't look like it in the diagrams

Originally Posted by ladas

Doesn't look like it in the diagrams

The transfer case temp switch, when installed, is on the same circuit.

As some of you know I am not the most mechanically minded here.

So if the Auto trans gets to hot is there an alarm or light that comes on the dash?

Last week at Stockton after getting down near the wreck and stopping I could smell a burning - hot smell. ( Auto TD5 ) Dropped some more air out of the tyres on the way back up the beach and no smell. Hope I did not cook anything? Any thoughts why the brief hot smell? Would there have been a chance of me cooking anything?

P.S. sorry about the slight hijack of this thread.

Originally Posted by ak

<snip>

So if the Auto trans gets to hot is there an alarm or light that comes on the dash?

<snip>

Yes - a red symbol representing a gear in the RH top corner. Its illuminated when its earth wire is grounded, but no alarm.