GQ TB42 radiator sensor question

[Bluedog77]

My GQ has two sensors on the radiator. One is at the top and one comes off the bottom hose pipe, both on drivers side. I assume one is the aircon cutout when hot but what is the other and which is which? I have been looking at a new radiator but I haven't seen one with the bottom sensor.

[the evil twin]

There are a variety of configs for the TB42EFI manual and auto and not all of them are in the manual.

It has been ages since I sold mine so cannot physically check but IIRC the Condensor Fan temp switch is towards the top of the Rad.
If you disconnect the plug and test the sensor it will be open cct when cold
If you short the plug the Condensor Fan will run.
I am reasonably confident the switch setting is 97 degrees because the standard Aussie thermostat is fully open at 95 degrees
Because there are 2 other thermostat settings available there may well be 2 other sensors as well

The A/C cutout switch is towards the bottom of Rad
If you disconnect the plug the sensor should test short circuit
If you short circuit the plug the A/C should be OK
If you open circuit the plug the A/C should drop out
The A/C cutout is set for 107 degrees and should close again at 102 on all models from memory

This should translate to the following
A/C off and Coolant below 97 - Fan off
A/C off and Coolant above 97 - Fan on
A/C on and Coolant below 107 - Fan on and A/C works
A/C on and Coolant above 107 - Fan on but no A/C operation
when/if Coolant drops below 103 - Fan stays on and A/C comes back on

Been wrong before and will be wrong many more times but that is my hazy recollection of the system

[Bluedog77]

Thanks for that very detailed information. I think that explains it very well. I reckon I still have the original radiator and it may be due for replacement.

[the evil twin]

If you are replacing the Rad then IMHO the genuine ones are very hard to beat for performance and quality.

If you are refurbishing the existing one then get it done professionally.
The GQ Rads normally have two issues;
- externally the bottom1/4 of the fins are hard to get at and get blocked with mud and bug guts etc which sets like concrete over the years so the rad looses air flow.
- internally the core gets blocked, the only way to 100% fix that is to have the core removed and rodded, after 40 odd years no amount of the chemical solutions and flushes will do the job by themselves.

[Bluedog77]

Yes not sure which way to go yet. I think new genuine ones are aluminium cores with plastic tanks now. Looking for a long term fix - so genuine or similar quality.