Temperature Switch? (newbie)

[TrekGTO]

I need help with what is probably a simple project?
I have a product for Super Charged cars where the intake air temperature is cooled with a water to air intercooler. We use the cars AC to refrigerate the intercooler water and use the AC compressor clutch 12V on/off to power our system relay.
Here is the problem, some new cars don’t have an AC clutch, they use the computer to control the compressor internally.

What I would like to do is change to a water temperature control. I need to power a relay below say 90deg F. It would be nice to be able to adjust the on/off temperature but around 90deg F fixed would be enough.

I need a 12V switch unit that would be closed below 90deg F and open above 90deg F. This temperature switch would power the 12V system relay. I already have a digital display showing the water temperature with system on or off.
I can do some simple parts assembly but need a reliable solution. I can make a custom sensor mount in a brass 5/8” or ¾” hose splice. Only recommendation I have so far is to use a thermal couple. Obviously the sensor needs to be water proof.

Possibly a THERMOSWITCH that opens at 90deg F that will fit into the brass hose splice?

Thanks for any help, Dave

 

[Diver300]

Don't use a thermocouple. They have really tiny output signals but they are capable of going to much higher temperatures than you need. They also need "Cold Junction Compensation".

For an electronic solution you should look at a thermistor or RTD https://en.wikipedia.org/wiki/Resistance_thermometer

Can you use the sensor that is used by the display at the moment? It might be possible to sense a voltage on the existing circuit.

 

[alec_t]

Google for 'bimetallic thermal switch'.

 

[TrekGTO]

Thanks for the information above. I found
Cantherm and
Devale
but I can’t find a supplier, I tried DigiKey and Mouser but nothing yet.
I believe the product I need would be an off the shelf part but no luck finding a supplier or part #. A small NPT probe with 2 wires or terminals that opens around 90/100 degrees would be great!

 

[alec_t]

How about a fan control switch (house or car radiator)?
https://www.google.co.uk/url?sa=t&r...k5Q54sORIDQcg7QhHtmPQ&bvm=bv.1355534169,d.d2k

 

[Joe G]

Just a thought, what about using the sensor from a drip coffee maker, the whitish one that turns the pot warmer on/off. Its the same type used also on my gas fireplace insert that turns the blower on/off. food-for-thought.

 

[TrekGTO]

I fixed the links above, Im looking for a water probe switch.

**broken link removed**

 

[alec_t]

Have you tried your local car breaker's yard?

 

[TrekGTO]

Have you tried your local car breaker's yard?

Cars don’t use anything close to what we need, this is a custom product for Super Charged modified cars.

 

[alec_t]

Cars don’t use anything close to what we need

A thermal switch is a thermal switch . What particular property does yours need that a typical radiator-fan switch doesn't have? Is the switching temperature wildly different?

 

[TrekGTO]

A thermal switch is a thermal switch . What particular property does yours need that a typical radiator-fan switch doesn't have? Is the switching temperature wildly different?

A typical fan switch closes when it gets to around 200 deg F. As stated I’m looking for a solution that opens around 90 – 100 deg F.

 

[debe]

Go look on Ebay plenty of 12Vdc adjustable temperature controlers for around $15.

 

[TrekGTO]

Go look on Ebay plenty of 12Vdc adjustable temperature controlers for around $15.

I already searched Ebay and got 0 results.

 

[debe]

When entering Ebay you need to try diferent combinations of wording to find what you want.

 

[gary350]

What are you trying to accomplish? From what you say I think your making cold air to give the engine more horse power.

Your sorta on the right track. Power it takes to run the AC compressor is more than power gained in horse power to the engine. Use a box of ice it works better.

Perfect fuel/air mixture is 15 to 1 for a gas engine. The computer is designed to make the fuel/air ratio closer to 12 to 1 this produces less hydrocarbons in the exhaust so your vehicle will pass the emision test but it wastes fuel. You need to LIE to the computer so it thinks your engine is sucking in 150 or 200 degree F air all the time this makes the fuel/air mixture closer to 15/1 ratio. Next work on making the engine run colder and make the computer think the engine is running colder. Replace engine water cooling therostate with a flat washer with a 3/4" hole. Replace old engine temperature sensor with a new one. Test 10 sensors with an ohm meter tolorance is plus or minus 5% pick the lowest resistance and use it. Replace air intake temperature sensor with a 1000 ohm resistor. Just to be safe remove the sparks plugs every 500 miles to see how they look. As long as the sparks plug tips are not white every thing is fine. After testing spark plugs a several times if the tips are never white the engine is not running too lean so no need to test plugs anymore unless you change something. Disconnect the AC pump and replace engine fan with electric fans. Open up the exhaust system too the less power you waste the more power you have to the wheels.

**broken link removed**

 

[KeepItSimpleStupid]

Go after the sensor voltage itself. See: **broken link removed**

 

[alec_t]

If you want a versatile switch you could build something like this:

This would give you control over both the switching temperature and the hysteresis (the difference between the open and close temperatures). You would need to epoxy the NTC thermistor into a suitable housing to make the temperature probe, but it sounds as though you have the facility to do that.

 

[Reloadron]

I would run with the circuit Alec posted. Simple and adjustable.

Ron