radiator fan switch

Jokester · November 03, 2009, 03:44:40 PM

On a small block Chevy, can I put a radiator fan switch in the block where the drain plug is? Right now the only place I have for it is in the thermostat housing. There is only one hole in the manifold and that's where my gauge is. Would that low on the block be a feasible location for either the switch or the gauge?

thx,

.bjb

enjenjo · November 03, 2009, 03:49:57 PM

No holes in the heads, near the exhaust manifold?

Jokester · November 03, 2009, 07:59:16 PM

Nope! No holes in the heads. It's a 63 327 with old heads. The manifold is an offy cross ram.

Is the drain hole that's low on the side of the block just above the pan a possibility? Would it give a reasonable indication of engine temp? I could put either the gauge or the fan switch there if it would work.

.bjb

Learpilot · November 03, 2009, 07:59:29 PM

I got the same problem. I got a radiator probe thermostst that goes into the fins of the radiator, and it works fine. I got it at Advanced Auto Parts.
Rick

phat rat · November 03, 2009, 08:02:28 PM

Another possibily is to have a radiator guy put a threaded bung in the lower radiator tank. That's what I did with mine. I used to have one that went into the radiator neck under the hose. I don't like the ones that just go into the fins.

Jokester · November 03, 2009, 08:48:28 PM

But the bottom of the radiator is the coolest part. I don't want to know how cool the water is, I want to know how hot it is.

Same for the fan switch. I'd like it to be somewhere that the water gets hot.

I thought about putting a tee in the only hole I have, but I'm afraid there wouldn't be enough flow to trigger the switch and the gauge may be reading low.

How hot (relatively) is the water by the drain hole in the block?

.bjb

enjenjo · November 03, 2009, 09:16:28 PM

QuoteHow hot (relatively) is the water by the drain hole in the block?

The problem is that part of the block quickly fills with gunk, and you can'i get a true reading.

Carnut · November 03, 2009, 10:24:45 PM

So either cut top radiator hose in half and put in a tube with a bung for the switch and clamp it in place or have a bung put in the top radiator tank.

phat rat · November 03, 2009, 10:44:16 PM

Quote from: "Jokester"But the bottom of the radiator is the coolest part. I don't want to know how cool the water is, I want to know how hot it is.

Same for the fan switch. I'd like it to be somewhere that the water gets hot.

I thought about putting a tee in the only hole I have, but I'm afraid there wouldn't be enough flow to trigger the switch and the gauge may be reading low.

How hot (relatively) is the water by the drain hole in the block?

.bjb

You said you wanted to use this to trigger a fan not use for a temp gauge. Use a rheostat/adjustable switch and you can set it by your gauge

rumrumm · November 04, 2009, 08:25:25 AM

Buy a thermostat housing spacer from Summit. They have two threaded holes so you can run two sensors. That is what I did. Very slick.

tom36 · November 04, 2009, 09:30:01 AM

I used this, http://www.centechwire.com/catalog/accessories/fc2p.shtml
on my '36 and as they say in Maine, "works *" Tom...

model a vette · November 04, 2009, 09:34:39 AM

If you want to use it to trigger the fan there is a Chrysler mini van fan switch which mounts in the lower tank of the radiator. It has a low turn on temp because of its stock position. I think the turn on point is 170-180 degrees.

rumrumm · November 04, 2009, 09:45:50 AM

Quote from: "tom36"I used this, http://www.centechwire.com/catalog/accessories/fc2p.shtml
on my '36 and as they say in Maine, "works *" Tom...

I also used the Centech unit Tom mentioned, and it works very well. If you place a sensor in the bottom of the radiator, you are measuring the cooled water while if you mount a sensor in the thermostat housing/intake manifold, you are measuring the engine temperature which will give you a more accurate reading.

papastoyss · November 04, 2009, 01:45:20 PM

Quote from: "phat rat"Another possibily is to have a radiator guy put a threaded bung in the lower radiator tank. That's what I did with mine. I used to have one that went into the radiator neck under the hose. I don't like the ones that just go into the fins.

I like the adjustable one that has a bulb that goes in the drain cock fitting . Use it to ground a fan relay & set the knob so the fan comes on when you want it to. The only down side is you loose the drain cock unless you install a second fitting.

32coupe · November 04, 2009, 04:01:30 PM

Quote from: "model a vette"If you want to use it to trigger the fan there is a Chrysler mini van fan switch which mounts in the lower tank of the radiator. It has a low turn on temp because of its stock position. I think the turn on point is 170-180 degrees.

This is what I have done and it works great

radiator fan switch

Learpilot