Temperature/fan Sensor

[Guest farmerp]

I am wiring up my car Can someone give me the phone number or link for a supplier for a electric fan sensor. This information seems missing from RH.......

 

Thanks

 

pf

[Guest Russler]

I presume you mean something like a thermostatic switch, I think car builder solutions do an adjustable one and from memory it is about £25. If not you can use the switch from a production car and make a sleeve to go in a pipe.

[Big Jim]

look on Premier wiring's advert, you can get a tube to go into the top hose with a boss on to take a switch. They also sell switches at different temps, or even 2 different temps for a twin speed fan (I have one of these) and the Ford fiesta switch (out of the thermostat housing) or the Vauxhall (out of the rad), too high in my opinion) fit this boss as well.

To wire it (whatever switch you use) I can recommend that you do it This Way

[Longboarder]

Another approach is to take your rad to your local rad builder and get him to solder a switch boss into the bottom tank. Neat, cheap and technicaly better solution.

 

Nigel

[Big Jim]

Why the bottom tank Nigel? I believe that it's the temp of the water coming out of the engine & therefore the temp of the engine that needs to be "controlled"

so if it becomes too hot, the fan comes on, instantly cooling the water in the rad more before it's pumped around the engine, thus cooling the engine down. If the switch is in the bottom tank of the rad, then you would need a much lower temp switch, because this is now the "cold" water that's about to go back through the engine. Not only that, you can get cold spots at the bottom, with any build up of rust & crap in the system.

Personally I think either in the top hose, or the top tank. (but if the water level drops, this will only work when it overheats, and is triggered by steam)

 

Off soapbox.

[Guest farmerp]

Thanks for the idea's all I will make one work!!!!!!

 

 

pf

[Guest Charles B]

I used one of the capilliary ones you slide into the top hose and clamp with the jubilee clip. It may sound crude, but it hasn't leaked, and works fine. I think I got it from Europa or Vehicle wiring products.

[Longboarder]

Jim, the way I thought about it is a fan trigger switch in the top hose or rad header is sensing water temperature leaving the engine with no way of knowing what the cooling airflow is. It will be set for a higher temp say 90 something and may run the fan pointlessly when you are doing 80 mph. With a switch set at say 75 in the bottom of the rad the water there has had the benefit of cooling by speed produced airflow and the fan will only run if cooling has been too little. That should be because the temp hasn't dropped enough because the rad is in reduced airflow. This all assumes a reasonably balanced system and if the rad is not up to cooling the beast at 80 mph, turning the fan on with a switch put anywhere is not going to help. It seems to me that the rad fan switch is best controlled by sensing how the cooling system is performing which it does in the bottom tank rather than sensing engine heat load which it does in the top tank. (This may of course be a load of old garbage)

I think you could write a fairly convincing case either way. Looking at a few cars the big manufacturers seem to put them all over the place.

Switch in top hose can lead to the fan running for ages after parking without effectively cooling the engine. Driving back from Donnington last year I got an almost flat battery because the fan switch temp (variable in top hose) was set too low and the fan was running all the way to Bristol. I then had a cuppa and the fan ran on for 10 mins or so while parked. When I restarted, the battery was only just able to turn the engine over.

 

Nigel

[Big Jim]

Just that to me the important temparature is the water coming out of the engine, that's what needs to be kept constant. If you're cruising at 70 mph, then the air flow should do the trick, if you are loading the engine more by hard acceleration etc. then the fan may be needed as the water heats up to "switch" temp.

you've said that you had your switch too low, and you've nearly drained the battery because the fan carried on running after parking up. I would suggest that you need to sort out your cooling system. My thermostat is open at 80º the fan kicks in at 87º and off at 83º (1st speed) the second much faster speed would kick in at 93º and off at 87º (down to the slower speed) this runs excellent, and I had no problems at all with it when I was blasting round France last year in temparatures of 42ºC

you also need to re-wire your switch as the diagram on our web site. it does work, believe me! you'll not flatten your battery then.

 

(For those that are curious, the 2 speed fan is from a Volvo 440, and sucks. the 2 temp switch is from Premier wiring.)

[Guest Phil Slater]

I had a mount for a temperature switch brazed into the RH supplied radiator at my local Rad repairer - a long, long established firm and without a blink they suggested they put it in the bottom. When I queried this they said it would work fine in the bottom.

 

To my simplistic mind whats needed is coolant going back into the engine with a low enough temperature to do the job it's intended to do. So, the sensor at the bottom ensures this. Does it not????

 

Phil Slater

[Guest Ant]

It's all swings and roundabouts. The point is that certain fan switching sensors are designed to work at the bottom of the radiator, some half way up, and some on the thermostat housing or top hose. Just get a sensor which is designed for your chosen location and it'll be fine!

 

Ant