[T3] heater thermostats

[Jim Adney]

On 30 Oct 2014 at 16:13, Dennis Stiefel wrote:

> This is the first time Clementine has had a stock muffler since 1984.  In
> this time I have had no issues with the way the heater functions as long as
> I kept the hoses from the fan housing to the heater boxes on.  I remember
> someone on here saying at one time on here that when you run an aftermarket
> exhaust and do away with the hoses coming off the elbows to the heater
> thermostats that you could run the risk of the heat getting so hot going
> into the duct work it could burn the paint off the rockers under the doors
> (I think). 

There seems to be a LOT of misunderstanding about how this system 
works. The thermostats in those boxes are there to mix cool air with 
the heated air in order to give you MORE heated air at reasonable 
temps, once the engine gets warmed up. Hence the name mixer box. If 
you don't have the ~1" hoses in place, hot air will spill OUT of the 
mixer box elbows once the air gets to the thermostat opening 
temperature, thus robbing you of heat in the passenger compartment. 
If everything else is working well, it's possible that the 
thermostats themselves could be overheated and come unsoldered, but I 
don't think there's any risk of burning paint anywhere.

The thermostats are okay unless you can look at them and see that 
they are expanded even when cool. This is exactly the same as the 
engine thermostats. Dead ones are often referred to as "popped." If 
you want to test them, you should bolt them into a spare engine 
thermostat holder and drop them into water that you heat on the 
stove. The holder will keep them from overexpanding and hurting 
themselves.

If the whole system is there and working right, even with the mixer 
boxes working right, reducing the heater output temperature, Type 3 
heaters will still put out very hot air, especially into the rear 
footwells.  

For best results, you want those ~1" cool air flex tubes to be in 
place. I have them in stock and they are cheap, $15/pr plus shipping. 
Treat them with care and they will last forever. Note that you will 
have to have the ~1" steel pipes that carry that air forward thru the 
engine tin in order to install the flex hoses.

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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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