1958 parts identification needed

[Christian Aicher]

Hi all,

Does anybody know what that membrane type housing with the two wires on next to the carburetor is? Is that the rpm advance for the A/C (when the A/C is on this should increase the idle?)? After the last drive I realized that my idle was not smooth anymore (with the A/C off) and when I checked under the hood, I found the red wire disconnected from the mysterious housing. I have not checked since, but I hope that my idle is back to normal now. So, what is that thing and how do you set correct?

Also, on the very right side of the picture there is another mystery housing which is linked to the carburetor linkage (mounted on the fire wall). Is this a kick-down switch? How do you set it correctly?

I have both shop manuals (57 and 58) but could not find an answer to the those questions, therefore any hlep/hint is welcome.

Chris

[Otto Skorzeny]

I don't know what you mean by "membrane type housing."  Are you talking about the solenoid that increases idle rpm when the ac is on?

If so, that is what it's for. It moves the rod to increase idle rpm when the ac is on. It's adjusted by turning the little wheel on the tip of the rod. (left in your photo)

[Glen]

The one on the fire wall is a dashpot it it is the one I think it is. 

The dashpot prevents the throttle from slamming shut and stalling the engine.  It just allows the throttle to close slowly. 

Glen 

[Otto Skorzeny]

Yes, that is a dashpot. It just keeps the throttle from dropping rpm too quickly and stalling. The one associated with the a/c is in the center of the picture.

I still don't understand what a membrane type housing is, though.

[Christian Aicher]

Hello Glen and Otto,

Please forgive a "darn foreigner"  for not knowing the right terminology, but to me that housing on the side of the carburetor with the red and blue cable in the back (that looks like a vacuum advance) looked to me like a housing for a membrane and I think that's actually what it is. The treaded rod with the knurled nut on it is probably mounted on a rubber membrane which is actuated by the intake vacuum. I assume that the two wires actuate a valve when the A/C is turned on to open the vacuum and pull the rod, thus increasing rpm.
But those were actually my questions - are my assumptions correct? Does anyone know where in the manual I would find a description of that "thing'?

Thanks, Chris

[Dan LeBlanc]

It's called the idle speed up control and increases engine RPM when the car is in park or neutral only and the a/c is on.  It is used to increase cooling when the car is parked (in heavy traffic with a/c on, pop your car into neutral  for example).

Should be in your shop manual in the accessories chapter in the section about air conditioning.

[Chris Conklin]

Just so you're not alone Chris, I understand the "membrane" reference. It looks very much like a common diaphragm regulator used in the natural gas industries. It contains a "membrane" that fluctuates and opens and closes a "cone-over-port" valve mechanism based on upstream and downstream pressure differences. Demand on one side moves the diaphragm to open the valve, loss of demand allows pressure to push it closed. It also provides protection from over pressuring the house lines. That's how the nat gas coming into your home is reduced to about 8" inches of water column from a medium pressure service line of 40#. As to your A/C idler, I have no idea how it works! 

[Glen]

Although I have some ideas about that unit, I think I’ll keep quiet because I’ll probably just confuse the situation.   

Glen

[Dan LeBlanc]

Although I have some ideas about that unit, I think I’ll keep quiet because I’ll probably just confuse the situation.   

Glen

I'd like to hear them.