CIS: What's this and what does it do?
 

I was removing my heater blower motor in the engine compartment and found the part pictured below. The ground was not attached, and thus not working. It is mounted on the rear mount bolt bracket of the heater blower bracket. What is it and what does it do? Ther eare two vacuum lines that run to it.

That part is called the thermovalve. It is used to assist in cold starts by making the WUR enrichen the mixture as if it were in full throttle enrichment mode. It is used on K-basic systems only (non-lambda).

The part should be closed when cold starting, and then open up when warmed by its internal heater.

I believe it is also called the auxiliarly air regulator. As previously said, supplies more air to the injection system when starting up (like holding down the throttle slightly).

-Wayne

So how can we test ours ??

Shawn

wayne-- That's not the aux air regulator. The AAR is on the other side of the motor. The thermovalve is a vacuum switch. connected between the throttle body and the lower vacuum input on the WUR.

Again, this is only used on SC's from 78-79 US, and all SC's ROW.

You can test it by putting it in the freezer. It should be closed when cold (I don't know what temp). Put it back in the car and let it run for a few minutes and it should be open.

It's item 17A in this pic.

http://www.pelicanparts.com/911/911_...8-83/1-7-2.JPG

This is a thermovalve. It mounts just below the aux air blower on the driver's side of the motor.

Bill any idea why my 77 2.7 has one?

Shawn

I don't know about the 77 2.7s. Do you have a vacuum diagram for your model? Noah's 77 3.0l is much like the '78 and '79 motors, so I'm not surprisded that he has one.

Does your WUR have one vacuum line or two?

Bill No I don't have the diagram. The warm up regulator on the parts site here looks exactly like the one in my car, but then again the WUR for mine looks exactly like the one for the 75 and for the SCs? Could be just the scetch but they look exact. Different part #s though (and prices)

How can I tell?

I wish I had a 3.0 like Noah! :rolleyes:

Shawn

It's on my '77 also. Oddly enough, I was fooling with the blower also the other day and couldn't figure out what it was either. It's the thermal valve on mine. It's a CIS thingy. wckrause is right but '77s have them also.

As for the test...it would seem that there should be a test for vacume and electrical, not temp.

Like, somethings got to suck first (vacume) then the electrical contact is made. Then that signal is sent somewhere. Most likely to the cold start valve. But the CSV won't fire if the signal from the Thermal Switch (part of the Oil temp sender) says that the engine oil temp is already warmed up. Not suppose to anyway.

Don't think that that device is a Temp. thing. So putting it in the freezer probably isn't going to do squat.

The electrical connection to the thermovalve is just to heat a bi-metalic bar that opens up the air passage. I've done the freezer test on my thermovalve, so I know that it works. Mine was stuck open, which was giving me cold start problems, because the WUR wasn't putting out a low enough control pressure on cold starts.

The thermovalve has nothing to do with the cold start injector. You're thinking of the thermotime switch.

Translation:
I put the thermovalve outside on the patio.

(Keep smilin', Bill :) ..... Summer is near!)

Yes, the cold start functions of the CIS get a real work out in my neck of the woods.

Beg to differ if I can. I think the part you're refering to that has a bi-metalic bar and opens an air passage and functions on a cold start is #36 on the above diagram. It's call the Aux. Air Regulator

The device in the first photograph is #17A on the diagram and as I mentioned, there is a vacume connection (to the throtle body and to the Diverter valve) and it has the electrical connection. And it's called the Thermo Valve by Haynes, not that they can be trusted. I'd attach a pic of the vacume and emissions layout but for some reason can't.

alan-

Both devices have a bi-metalic bar and heater that opens and closes an air passage. The aux air regulator (#36) provides more by-pass air to cause a higher idle during cold starts. The thermo-valve (#17A)closes off the vacuum to the WUR during cold starts to reduce the control pressure and enrichen the mixture.

I've got the Haynes manual, and the same vacuum diagram that's in it is also on a sticker on the rear deck lid of my car. The Bentley manual doesn't mention a thermovalve nor show the correct vacuum diagram for the 78-79 SC's

I was able to start the motor cold for the first time since reconnecting the topic component. All it did was hold the high idle on for a longer period of time. I never had any problems starting when cold. And since it never drops below 60 here in So Cal, it's prettty worthless.

Try starting a car at 20 below without it! It causes about a 10-15 psi drop in control pressure.

Bill, Ok it's worthless to me. SmileWavy

You guys back east are the pros at the cold start, that I do not doubt.