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Has anyone fitted these switches in the top hose, i have a T piece, that is not doing anything now, in the r.h. top hose
and am thinking of putting it in this, what would be the ideal temp switch to get in that position?
Rex
I would not advise it, because the relevant temperature is the temp the water is entering the engine at, not leaving it. At a standstill, the amount of heat removed from the coolant by the rad is not the same as when blasting along at 80 mph, but the exit temp of the top hose might be the same in both cases.
Secondly, in traffic, the acceleration as you move forward a few yards, puts a blast of hot coolant into the top hose, even though the rad coolant might be quite OK, so this would cause the fan to cycle on and off, thus stressing the relay and the fan motor with constant starts and stops.
Greg
Last edited by Greg in France; Dec 12, 2020 at 09:27 AM.
You would need to do some time testing of the top hose temps of YOUR car. And every car is different in that aspect.
Top hose sensing has never been successful, and am not talking only Jaguar.
Way back in the 70's, many thermo fan operated cars were out there, and their sensor was always in the bottom hose section of the cooling system, due to temperature stability.
The instability of the top hose is due to the constant "opening/closing" of the thermostat.
Running a generic temp gauge sensor there, and the gauge inside the cabin, and drive around, record the readings, and select a switch if that is what you really want to do.
Down here, that factory switch is 85C, and I use it for my thermo fan installation, and NO issues at all.
In the early days, a very long time ago, I used one of those "top hose" probe type sensors, and never, ever got it to work satisfactorily in that position. I moved it to the bottom hose, and Bingo, sweet as I wanted. It was NOT a Jag, my sisters Holden was the beast concerned.
Last edited by Grant Francis; Dec 12, 2020 at 06:27 AM.
The switch in that hose at the moment is connected
to the other switch and activates at 80 degrees, it's a sort of back up, I always drive with the a/c on so the twin fans, from Dallas but with Spals. are permanently on. Just wondered about the pump switch.
Water pump fan thermo switch
