EA81 thermo fan cut in/out points

Smokey · Post by **Smokey** » Fri Nov 11, 2011 2:59 pm

I'm keen to learn more about how L and Brumby dual elec fans with AC operate. In my S1 L (1986) the temp sender is a dual plug one that appears to turn on (close the circuit) at approx 90C, off again about 5 lower. This one was located in to side top facing the fender or outside of the car. The AC one though is hollow inside and had the wires attached to it, its closed all the time, and I don't think broken (though yet to confirm this). It was located in the lower backward facing slot in the same tank. Facing the engine or the rear of the car. Replacing it with a normal one that opens and closes to specific temps will prevent the AC compressor form kicking in until the temp is hot enough to close the circuit.

What does everyone else have?

nncoolg · Post by **nncoolg** » Fri Nov 25, 2011 5:30 am

I've got a six month old one of these I just took out :
TFS156 Fan switch Thread - M16 x 1.5
Circuit - Normally Open
Temp Range: 87ºC to 82ºC
Spanner - 22mm
good cooler option if anyone wants it...

revmax · Post by **revmax** » Fri Nov 25, 2011 2:50 pm

for what it is worth. My Brum has air con and two thermo fans.
The passenger side fan comes on throught a relay that is activated via the thermo switch in the radiator. BUT the drivers side fan also comes on at the same time BUT power to the fan was not going through a relay but directly through the thermo switch peaking at 10A on startup, which is probably why the thermo switchs kept crapping out.
I have unpluged the drives side fan to prevent the thermo switch from blowing again untill a time when I can hook up another relay to the second fan.

Pootcrum · Post by **Pootcrum** » Sun Nov 27, 2011 2:07 pm

Hey guys thought I would chime in on this as I am dealing with similar issues.

So I replaced my radiator and one of my electric fans about 6 weeks ago. Thought I might as well replace the thermo switch while I was at it and got the TFS195 as per the Tridon catalogue.

This weekend while I was parked in the city waiting for the gf the brumby temp went way up, near to the red, which was not normal for my girl. Got out, popped the bonnet and found coolant pissing out and the fans not running. Ghetto fixed it with what I had on me so that the thermo switch circuit was permanently grounded to get me home.

Anyway, today I tested my switch and sure enough in a pot of boiling water there was no love, the circuit was open.

Now the TFS195 has a single pin that is connected to the thermo switch circuit, and the ground connection is made through the body of the switch and thus the radiator and body. My old switch however had two pins, one was connected to the thermo switch circuit while the other was connected directly to ground. Originally I figured this was merely an older but equivalent way of doing the same thing. But after reading this stuff and thinking a bit I am wondering if it is not.

My old switch appears to be most similar to the TFS183. It looks almost identical in fact. The temp range is 5 degrees higher than the TFS195 but that should mean the latter will keep the car 5 degrees cooler (though it definitely does not in my case). A significant difference from what I can tell is the circuit diagram given on the website here.

TFS183

TFS195

To me, it looks like the TFS195 circuit is designed to carry a voltage, while the TFS183 circuit is designed to carry current. I know there are some nitpicky things wrong with what I said there but I think that difference may be significant.

So my thought was this. What if the TFS195 is only meant to carry a very small current to ground, while the TFS183 is designed to be in series with a fan circuit and thus is capable of carrying a higher current? It has already been mentioned that the A/C mods to brumbys were aftermarket and I would be willing to bet that there would be some discrepancies in the way in which it was performed. What if the circuit is allowing to much current flow to ground when the thermo switch activates and thus they die prematurely? And would the TFS183 be a more appropriate choice of switch in these situations?

Thinking out loud here guys, any thoughts or hole-pokings for my theory are more than welcome. Regardless, my old switch is going back in and I am hoping that my temps will be more stable. Will also be contacting Tridon to ask about a guarantee since on the packet it says 2 years.

EDIT: Just took the girl for a spin with the old switch (suspected TFS183) and the fans kick in at a shade over halfway on the temp gauge and turn off a shade under it. It remains far more stable than when I was using the TFS195. This doesn't necessarily mean that the TFS195 is wrong, since it doesn't work anymore it may have been faulty in the first place, but I am not convinced that it is the right choice either.

phantomD · Post by **phantomD** » Tue Nov 29, 2011 4:42 pm

Definitely agree with you there. I've blown up three colder aftermarket switches...plan here was to install another relay to stop the fan current coming through the radiator.

steptoe · Post by **steptoe** » Tue Nov 29, 2011 7:23 pm

current and voltage are different eh ? OK, maybe use the nmewer switch to switch an added by you relay ?

Pootcrum · Post by **Pootcrum** » Wed Nov 30, 2011 10:51 am

phantomD wrote:Definitely agree with you there. I've blown up three colder aftermarket switches...plan here was to install another relay to stop the fan current coming through the radiator.

steptoe wrote:current and voltage are different eh ? OK, maybe use the nmewer switch to switch an added by you relay ?

Yeh I guess that was the crux of my argument. I think the TFS195 may be designed to switch a relay, whereas the TFS183 may be capable of both switching a relay, or simply allowing the current to pass straight through the switch itself. Kind of need an auto elec to comment. Regardless, I am not dicking around with it at this stage, my old switch is working fine still. Strengthens the old saying "if it aint broke don't fix it".