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Location of thermal switch for fan


Les Henson

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In the past it seemed that the only place to fit one of these was at the top of the cooling system, but could it be elsewhere? Most makes of cars have the switch halfway down the side of the radiator. To my way of thinking near the bottom would ensure the fan cooled the engine at the right temperature even if the radiator wasn't working efficiently. Does it matter as long as the switch is after the thermostat?

Les. :)

Edited by Les Henson
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Well, kenlowe say to put the capillary into the top hose, but most car manufacturers put it half way down the matrix presumably to get the "mid point" temperature in the rad. A guy in the club has araldited RS thermoswitches to the top of his rad to good effect.

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I have a Series rad so can't mount it mid-way as far as I know. I'm not going to use the Kenlowe sender as they are a bit unreliable. I was hoping to use an electrical one that's fitted to normal vehicles, Bullbar Cowboy has a very tidy arrangement for this type of fitting in the top hose. I just wondered if it would be better elsewhere.

Les.

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The one I use is the type found in irons and showers, and is surface mounting. I flattened a few of the fins, applied heat transfer grease and held it in place with cable ties. Obviously it works the fan through a relay.

My real concern is that it is a bit exposed to the elements.

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I have a Series rad so can't mount it mid-way as far as I know. I'm not going to use the Kenlowe sender as they are a bit unreliable. I was hoping to use an electrical one that's fitted to normal vehicles, Bullbar Cowboy has a very tidy arrangement for this type of fitting in the top hose. I just wondered if it would be better elsewhere.

Les.

Presumably you are referring to the ones with a 22mm or so thread that screw in to the rad on most cars?

If so, what is the cheapest source for them? Also, what is/are the best switching temperatures for Land Rovers?

Si

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Presumably you are referring to the ones with a 22mm or so thread that screw in to the rad on most cars?

Yes.

what is the cheapest source for them

They range from around a fiver to really silly money depending on the vehicle.

Also, what is/are the best switching temperatures for Land Rovers

You see, alls going well and then you go and ruin it by asking me something technical :angry:

I don't have a clue Simon, and it's slightly worryng that you don't know.

Les. :)

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kenlowe suggest just above normal operating temp, so, what, 90° - 95°? the procedure is to let the engine get warm, allow it to then overheat minimally, then adjust the thermostat until the fan starts.

nothing above 100° obviously, in case you were operating without antifreeze.

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Demon Tweeks do/did a bit to fit in various sizes of hose and take a 22mm threaded sensor, like what BBC made. IMHO the advantage of using the 22mm sensors is the ability to have duel temperature switching, unlike the kenlowe/pacet sensors which are single temperature only. A 22mm housing could be braised onto a rad if you wanted to read from the rad directly and don't have a 22mm fitting in the rad already.

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If you talk to one of the specialist re-corers they'll probably braise the bosses for the 22mm thermoswiches into a radiator for a couple of quid (especially if they're re-coring at the same time).

Is the way I got mine done, and if you get 2 bosses you can also add a 110 degree thermoswitch and wire up a warning light too.

Rasons Radiators did mine and I know of at least 1 person who has used Pirtek in Exeter (and they're a national company), and there are several other re-corers who I've heard have done the same

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Les,

Top hose is preferable as this is the hot water outlet from the engine before cooling. Some motors have the switch mounted in the thermostat housing.

In answer to Mike’s Question …….. the top hose is the hot water outlet from the engine before cooling .

I used an Intermotor 50091 M22 twin switch. The lower setting brings on the twin fans in series (half speed) and the hotter switch changes the fans from series wired to parallel wired (fast speed). When Charles (BishBosh) used it on his Range Rover we needed a slightly hotter switch.

Although I made up a top hose adaptor, it would have been just as easy to have soldered a 22mm boss into the Rad tank.

The big problem with the Kenlowe type capillary switch is the on /off hysteresis is way too large to be comfortable (for me anyway) …… also they are not water /plop friendly. Also capillary switches suffer from heat soak in the engine by giving rise to erratic switching behavior ;) .

Emailed you all the details. ;)

Simon .... pm your email address and I will send you the intermotor Rad switch listing.

Ian

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