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Mopar318
GenII
2/19/2006
14:18:50
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 Subject: Capillary tube broke on thermostat......
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I finished intalling my Proform fan with thermostat this week and all was going well. Took me about 2 hours to figure out how to mount it in the limited space in my Gen II. Got it all mounted and got every thing wired up. Then i relized I had to put the sensing bulb on the radiator to read the temp. I went to bend it to try to get it in place and the little gas filled capilary tube with the bulb on the end broke off . Any heating or cooling person should know what this is..Well now I have no idea how to fix my mistake. I should not have tried to bend it that much so its my fault not the fan makers. So does anyone know how I could put a new sensor thing in or any other way fix it? Thanks..
My rice eater
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GraphiteDak
GenIII
2/19/2006
15:09:27
| RE: Capillary tube broke on thermostat......
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Message:
oops. I just posted for you in the members area.
I'll just paste what I posted there...
The gas in that bulb was a referigerant. Higher temp = higher pressure which pushes against an adjustable spring to open/close contacts for the fan.
So bacially it's not fixable. Just have to get a new fan control.
My bro in law has one like that where it plugs into the radiator. And since he ran it right off of the battery his goes on and off a few times after he turns the truck off since the temp warms back up a little each time after the fan stops.
I used a electrinc control to power a relay and it only powers when the key is on.
If your handy with soldering simple circuits from Radio Shack I can tell you what to buy and what you need to build one that triggers off of the factory temp sensor on the engine.
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GraphiteDak
GenIII
2/19/2006
21:47:05
| RE: Capillary tube broke on thermostat......
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Here's the schemactic I said I'd post.
I started to draw one up and found I already had one on my website...
I'll post it here in your post in the general area in case anyone else wants to build one.
That's what I built from my Dakota.
You adjust the pot to set the turn on/off temperature. The input goes righ to the stock engine coolant temp sensor.
Should cost around $10 or so from Radio Shack parts. Maybe a few dollars more for the project box and molex connectors...
That's mine. Been installed for just over 2 years still working!
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GraphiteDak
GenIII
2/20/2006
16:10:57
| RE: Capillary tube broke on thermostat......
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Message:
I forgot to mention how the circuit works.
The stock sensor on our trucks outputs a varying voltage back to the PCM based on coolant temperature. I noted that the voltage DROPS as the temp INCREASES.
So my circuit uses a comparitor circuit. The reference voltage is developed by adjusting the variable resistor (pot) and that feeds into the (+) side of the comparitor IC. You connect the temp sensor on the truck to the (-) input of the comparitor IC.
(The 1k resisor in line there is just to limit current in case something shorts or you connect something wrong in the project box. So I would connect that 1k ohm reisitor on the wire tap right at the connection to your sensor wire. It's just protection not to burn up your PCM/Sensor if you short your wire to ground or 12VDC, etc.)
What the IC does is it has an output pin that is either on or off (12VDC or 0 VDC)
When the (-) input drops BELOW the (+) input reference voltage the output goes ON. That output drives a general purpose transistor to switch your relay to turn your fan on.
Anyone can use this simple circuit to control a electric fan more accurately than them stick in t-stats.
The IC has 4 comparitors and only one was wired as shown. You COULD get cute and use a second comparitor on the IC with a seperate pot to adjust that reference just a tad warmer. Then STAGE two fans if you are running two fans. Then when the temp is mild only ONE fan runs unless it can't handle the heat, the second one comes on too.
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myoung
Dodge Dakota
JOIN HERE
3/06/2006
03:35:50
| RE: Capillary tube broke on thermostat......
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Wow! Great circuit. I am going my my schools parts room that is just full of almost every thing I need(hopefully). I may have to buld one sometime this week.
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GraphiteDak
GenIII
3/06/2006
15:55:31
| RE: Capillary tube broke on thermostat......
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Message:
That would work. Otheriwse it's pretty cheap to buy the parts from Radio Shack or even cheaper ordering from digikey
Maybe I should redesign it for up to two stages (to run two fans based on temp) and have the boards etched professionally and sell these things.
I could always sell them on ebay :)
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myoung
Dodge Dakota
JOIN HERE
3/08/2006
15:00:48
| RE: Capillary tube broke on thermostat......
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Message:
I got it built and in my truck but it comes on too late. What can I change to make it come on sooner?
Thanks
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GraphiteDak
GenIII
3/09/2006
15:22:30
| RE: Capillary tube broke on thermostat......
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Message:
OK. SO you got it working right?
ANd you used the potetiometer (variable resistor) as shown?
That is the REFERENCE VOLTAGE to the comparitor.
You turn it with a screw driver a little at a time. One way sets it warmer and one way colder.
I believe setting the potetiometer to a HIGHER output refernce voltage makes the fan come on EARLIER. Since the voltage from your engine's truck sensor DROPS as temp RISES that should do it.
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myoung
Dodge Dakota
JOIN HERE
3/09/2006
22:36:53
| RE: Capillary tube broke on thermostat......
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Message:
OK, so after looking into it further it is not working. It was the factory system that kicked the fan on. After looking up the specs on that chip, i noticed that ground was not hooked up. So i soldered in that and still nothing. Just to make sure, you hooked the temp sensor input to the brown wire on the sensor behind the alternator and ac comp? Any better places to tap into? I will try and rebuild the circuit again on a solderless bread board and see what happens.
Thanks
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myoung
Dodge Dakota
JOIN HERE
3/12/2006
14:47:55
| RE: Capillary tube broke on thermostat......
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Message:
Well, I finally got it working, not sure what the problem was, but it works great now. Thanks again for the circuit.
BTW, your website is great, more info than one will ever need. I did the TPS mod at .75v and the idle is much smoother now. Thanks again!
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