The 'E' Type Forum

The engine cooling fans on my 1970 S2, come on with the ignition switch, and remain on until the switch is turned off. This seemed odd to me, thinking that they should be thematically controlled, and I assumed that the fans had been "hot wired" by a previous owner. Something that I read on this forum, recently however, has me wondering if they were factory wired to be on all the time?
Thanks,
Mike

I don't know what you might have read but the fans were not wired by the factory to be on all the time. The fans are controlled by the "Otter" temperature switch which on a Series 2 is at the top of the radiator and switch the fan motors via a relay.

That said, if you have a Series 2 with factory fitted AC then there is second relay that switches the fans on whenever the AC is energised, perhaps that has led someone into believing the fans are switched on all the time.

No, shouldn't be on all the time. The otter switch should control that. Some series 1 owners installed a switch on the dash so they could manually put them on; overheating can be a thing with series 1. Not so with series 2 with the bigger mouth and twin fans.

SORRY, posted same time as John's post so a bit repetitive!

No, they are not wired to run permanently. There should be an Otter switch mounted on the water system somewhere - I don't quite know where offhand, but the otter switch provides an earth connection from the radiator fan relay which then switches the fans on/off at appropriate temperatures.

If either the switch or relay fails, some directly wire the fans to run all the time as a rescue procedure - never removed on yours, evidently.

Hope that helps, Jerry

I would check to see if a PO has installed a manual override switch to enable you to turn the fans on manually.

Have a look in the driver's footwell and check at the fan relay for extra wiring.

Hello Mike,
As well as the suggestions already provided, check the resistance between the two terminals on the Otto Switch, used to turn the fans on and off (in the absence of an after thought, additional switch), when the engine and coolant are cold. If it shows Infinity, the original circuit is open (as it should be) and something else is switching the fans on.

Regards,

Bill

Thanks everyone. I have verified through documents that were included with the car that the stock radiator was replaced and there is no sign of an "otter" switch on the new one. Also, no manual override switch found.
Other than the additional wear and tear on the fans, is their any harm in letting the fans run? It seems with the "limited" miles that the car will be driven, the fans should still last a long, long time. I have owned the car since last October (about 500 miles), and the engine seems to warm up promptly, and run in the normal temperature range.
Thanks,
Mike

Mike...otter switch is typically on the front, of the rad at the top.....not easy to see....Steve

Mike, as Steve says it’s in the top of the radiator, can you see any wires going to the rad? It’s just to the side of the radiator cap.

Geoff

Believe I've found the otter switch on the replacement radiator, although it doesn't appear to be connected. Tough to see with the the clamshell hood. I only see one spade connector in the center of the switch?
I've recently been able to contact the previous owner of 40 years, who confirmed that he had the fans wired to the ignition prior to installation of the replacement radiator, when he was having overheating problems. I suppose that the shop that installed the new radiator, simply left the fan wiring as they found it. Unfortunate!
Per my last post,
"Other than the additional wear and tear on the fans, is their any harm in letting the fans run? It seems with the "limited" miles that the car will be driven, the fans should still last a long, long time. I have owned the car since last October (about 500 miles), and the engine seems to warm up promptly, and run in the normal temperature range."

Thanks,
Mike

Hi Mike...its your call.....most here would have the fans working correctly........its obvious that the fans wont last as long running continuously.....and the coolant entering the engine will be cooler than it should be......it wouldnt take much to wire it in.....your car.....your decision.....Steve

Mike, that’s the Otter switch, one wire to earth(ground) the other to the central tag.
Have you got the maintenance manual as there are wiring diagrams to explain how it is all set up, also look in the knowledge section there is a lot of help there, including the maintenance manual but you really should buy a copy as well.

viewtopic.php?f=16&t=700

Geoff

Hi Mike

As Steve said, most here would correct the wiring. As would I.

As it is currently wired, in addition to the wear and tear on the fans, your car will take longer to warm up and will generally run cooler than would be the case if wired correctly. That would also affect economy and engine wear. Your heater will also be less effective, if that mattered. Don't forget the constant noise from the fans too.

Another downside is the fact that the fans will be switched off when you switch off the engine. Sometimes it is good for the fans to run on after shutting down the engine.

Your car, your choice.

Regards

Thanks, all, for your help! I'm learning a lot. don't have a maintenance manual yet, and I'm no mechanic, but have a friend (TR2 owner) that is, so maybe I can ask him for some help doing the conversion.
Mike