My 88 TD 4x4 Auto Townace is overheating. To help keep the heat down I usually turn the a/c off and turn the heat on full blast to wick heat from the engine. I recently noticed that the 2 electric fans on my horizontal radiator don’t turn on even when the van is really hot. I then thought the fans weren’t working properly. But after trying to decipher the electric diagrams for the van I don’t think these fans are even intended to turn on when the van gets extremely hot. I now think they only turn on when the a/c is turned on (and mine do turn on when the a/c is on). Is this the way these fans work? If so, do you think the heat reduction benefits of having these fans on is counteracted by the increase load on the engine (thus increase heat production) from running the a/c? Would it be possible or even fruitful to try to wire up a toggle switch to this fans to get them to go on without having the a/c go on?
Thank you guys for all your help.
- (#13950) Lee Laskin, 29 Oct 04 16:32

These two fans, above the horizontal radiator are, as you point out, part of the A/C system. However, at dangerously high, engine coolant temperatures (103C I believe) these fans do switch on to assist the main cooling system. They are triggered by one of the two sensors mounted at the top coolant outlet from the head, near to the filler cap and, yes, I think that they do "trigger" irrespective of the A/C. However, others might be able to confirm this.

- (#13950) John Davis (Leics), 29 Oct 04 18:08

Yup. All you need to do is wire a toggle switch accross the thermal switch atop the outlet housing on the cylinder head. One is to defeat the a/c at high temps (114c IIRC), the other turns the fans on as John says. I can't recall which is which but it's easy to verify- turn the a/c on, and if you pull the wire off one and nothing happens, touch it to earth and the fans should run. If the a/c turns off when you pull the wire off, it's the other one...

And yes, this is then irrespective of a/c being on. Actually, if you have a/c on, the fans should be running at half speed anyway...

- (#13950) David Miller, 30 Oct 04 02:25

Thanks guys. i might install such a toogle for emergency overheating situations.
take care
lee

- (#13950) lee laskin, 30 Oct 04 02:36

Yes, that might be a help but, if all the other cooling fault possibilities are attended to, it should not be neccessary. If you pull off the wire, from the head sensor, and connect it to ground, you will bypass the sensor and can easily check that the fans start up and your toggle switch can be fitted into this sensor "bypass" link. I should not think that this procedure will affect the A/C operation in any way but, others might like to comment.

- (#13950) John Davis (Leics), 30 Oct 04 03:02