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914World.com _ 914World Garage _ Thermostat Question
Posted by: pbanders May 4 2022, 09:16 AM
While I may have done a transistor-by-transistor analysis of the ECU and used pSpice to simulate the injector driver circuit, I've never done squat with my thermostat system. Basically, it works, so I leave it alone.
But I'm curious, how do the bellows work? When the car is hot, the bellows expand, and the cable tension is released. Is there an internal spring? Something about wax? Help me out here, thanks.
Posted by: mrholland2 May 4 2022, 09:17 AM
While I may have done a transistor-by-transistor analysis of the ECU and used pSpice to simulate the injector driver circuit, I've never done squat with my thermostat system. Basically, it works, so I leave it alone.
But I'm curious, how do the bellows work? When the car is hot, the bellows expand, and the cable tension is released. Is there an internal spring? Something about wax? Help me out here, thanks.
I think there is a spring on the flap shaft that pulls against the thermostat.
Posted by: Mark Henry May 4 2022, 09:35 AM
While I may have done a transistor-by-transistor analysis of the ECU and used pSpice to simulate the injector driver circuit, I've never done squat with my thermostat system. Basically, it works, so I leave it alone.
But I'm curious, how do the bellows work? When the car is hot, the bellows expand, and the cable tension is released. Is there an internal spring? Something about wax? Help me out here, thanks.
I think there is a spring on the flap shaft that pulls against the thermostat.
Close, the spring on the flaps opens the flaps and provides tension for the cable, as the bellows expands/contracts it lets the flaps move.
If your T-stat bellows is always expanded then she be fuched.
Posted by: 914werke May 4 2022, 10:08 AM
Brad are you are asking what is contained inside the unit that causes the bellows expansion?
I believe it is a wax that liquefies when up to temp?
Posted by: mepstein May 4 2022, 10:21 AM
Always test it inside the bracket or it will over expand.
Posted by: emerygt350 May 4 2022, 11:42 AM
I ripped my old one apart pulling it out of the car, I think it is a bimetal design perhaps? There was no 'wax' inside the bellows. Or perhaps I let all the magic smoke out when I ripped it open with my pliers.... Seemed more like a metal expansion contraction type device. Not a spring inside though, unless it is contained within the bellow portion. I think. I was kind of pissed at it for how stuck it was.
Posted by: pbanders May 4 2022, 12:43 PM
Here's a 914 thermostat in operation:
https://www.youtube.com/watch?v=WFrcKSB-oUM
From what I can tell, it's a metal bellows filled with wax, which expands when heated and contracts when cooled. Old tech, but it works.
Posted by: barefoot May 4 2022, 01:19 PM
This may help:
Posted by: iankarr May 4 2022, 02:00 PM
I believe there’s a liquid (alcohol?) sealed inside the bellows and heat causes it to turn into a vapor and expand…
Posted by: pbanders May 19 2022, 11:08 AM
Ian Karr is correct, the working fluid is alcohol. Richard Atwell has an excellent page on the details of the thermostat, with all the info you'll ever need.
https://ratwell.com/technical/Thermostats.html
Oh, and I received my new thermostat from Awesome Powdercoat, a very nicely made component. As my existing thermostat seems to be working fine, this new one will go into my spares cabinet - which is getting fuller all the time.
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