About Tr8 Fans Cut Out Switch

[Chris59]

Hello guys,

 

I'm still playing, in my few spare time, on an ex US, carburetted + air con TR8.

 

I've removed all the air con parts (I'm allergic), and rebuilt a standard TR7 heater with new radiator and all anccilaries to fit under the dashboard.

 

But it's not the problem : I've also modified the cooling fans wiring loom for something far more simple, and now need to find the temperature cut in/out of the sensor in the radiator (a rebuilt standard TR8 unit) : is there here any TR7 V8 or TR8 owner who could help ?

 

Thanks in advance,

 

Edited October 13, 2013 by Chris59

[TR8IAN]

Hi Chris,

 

Hope all is good with you.

 

I'm sorry I can't help with the electrics (not my field). can I suggest you send a PM to Odd in Sweden (he does post on the forum) who has a modified TR8 and is likely to have done that sort of modification.

 

Other than that - does the car overheat? my car is still just running with the standard viscouse fan and has been fine without an electric fan.

 

Cheers

Ian

[John390]

The sensor should be at one end of the radiator, the drivers side if I can remember correctly. Mine has been bypassed so the fans are on all the time.

 

Cheers John

Edited October 14, 2013 by John390

[Chris59]

Hello Ian,

Yes, I'm fine, and you ? No viscous fan on a TR8, but 2 electric fans working one after the other : they are now connected to work together, but start to early, thus not allowing the engine to reach it's "operationnal" normal working temperature.

 

John, it's not a good idea : as explained previously, over cooling an engine is as bad as overheating !

[John390]

The car came over like it and 13 years later I have still not fitted a new sensor! But the engine does run a bit warm!

 

Cheers John

[Odd]

OK, I've read the comments - I sincerely hope you've not taken too much (i.e. the logic = relays etc.) out of there! If you have, please don't ask me I can't help you. If the logic is still there I'd be glad to guide you through getting the twin fans working as they were designed to - but on a single (two temp range) sensor and if needed with an inoperable AC... It's quite an ingenious setup giving the best electric fan operation I've ever seen with two fans working together at low speed and at high speed! Always working together and never just one at a time. If your fans do that - something is really really wrong...

/Odd

Edited October 14, 2013 by Odd

[Chris59]

You are right, they were working together with a ballast resistor in serie to make them turn slowly at low speed (but using as much current as at high speed ).

 

I've removed all this wiring, as everything was out of use (burned), and absolutly not necessary on a non air con engine.

 

It's very easy, if necessary, to re-make this kind of wiring myself, but I don't consider this as an option : all I need are 2 fans, working together at the highest speed, for a short periods, allowing the engine to stay at its ideal working temperature, piloted (via relays) by a sensor in the radiator.

 

So, is there here somebody who can tell me the temperatures indicated on his radiator sensor, ideally on a TR7V8, without all these TR8 "logic" ?

[AnthonyF]

In the original set up the rad switch turns on the fans at 199F (original thermostat fully open at 190F). I believe this corresponds to the half way mark on the temp gauge. Sorry but don't know the cut out temp.

[Odd]

Ballast resistor?!? That's what I thought, something must have been really really wrong in your car.

 

There should not be any ballast at all in the radiator fan circuit, just three relays, two fans, two temp switches - and that's it. In low speed mode the fans are connected in series with each-other (= half voltage each) and this is changed to a parallel connection (at full voltage) to get high speed mode. No need for any power eating resistor...

[Chris59]

Just back from holidays in the Vosges and Alsace areas, East of France, mmmh, those wines and food are so good !

 

@ Anthony, I'll follow this, it has been confirmed by another forumite (forumate !) : 199°F is about 92/93°C, so I'll use a 92/88° switch.

 

@ Odd, as write previously, the fans wiring was burned, the ballast resistor system may be the culprit !

Whatever, it's now modified/rebuilt and should be as reliable an effective as it can be.