custom electric radiator fan switch

[eschneider]

Lotus twin cam, installed in a Morgan. It has an aftermarket electric fan - but the temp sensor wire has been removed. I am contemplating just using a fan relay switch, wired to the motor via a relay.

Sensor will go in the stock threaded hole below the thermostat housing (green arrow pictured below) Whatever was there before has now been brazed shut and re-installed.

Questions:

1) what was supposed to be there (just curious)
2) is there a better spot for a sensor on this motor
3) at what temperature should the fan come on, measured at this spot on the head? The lowest commonly available switch activates at 219 degrees F.

yes, I know there are kits with adjustable controls, but:

1) I hate the clunky-ness of the control box under the hood
2) most of these use radiator-fin probes or something similar which might be fine for a Chevy pickup, but would detract from the mechanical elegance of a Morgan.

 

[DrEntropy]

It was originally an ether bulb fitting for the dual temp/OP gauge, Eric.

IMHO it is an outstanding place to take th' twink's temperature, but finding something that'll trigger at 185°F may be problematic (nudge-nudge).

2) most of these use radiator-fin probes or something similar which might be fine for a Chevy pickup, but would detract from the mechanical elegance of a Morgan.

Or a Lotus 1600 twin-cam! Have you looked to Grangier or equivalent?

I've not, but just tryin' to toss out alternative ideas.

...and I owe you a call. Mebbe t'morrow.

 

[eschneider]

finding something that'll trigger at 185°F may be problematic....

...and I owe you a call. Mebbe t'morrow.

The thread seems to be 3/8NPT or 5/8-18(UNF). If not, then it's british pipe. In any case, I can drill and tap the plug that's in there now to accept anything between 7/16 and 1/2.....

185, you say? That's a lot lower than anything in my standard ignition catalog - gonna have to do some digging.

 

[eschneider]

Decided to go with a manual switch for now and ditch the controller -- get the car on the road the quickest.

In the meantime, if anyone stumbles across this thread after it's dead and gone, I would still appreciate any comments for future refernce and general knowledge.