1969 Vacuum actuator part numbers

[William D.]

Hi Gang,
It's been awhile since i've posted here. Still plugging away at restoring my 1969 Convertible 427/390 w/AC. The deeper I go the more I find I need to fix or replace. I need the GM part numbers for two vacuum actuators. The first one is in the box that the heater core sits in (selector assembly # 3949877). The other one is in the box that directs air up, down or both (distribution duct assembly # 3946979). Each of these actuators has two vacuum hoses going to them. They both leak on the shaft side of the actuator so the diaphragm is good but the shaft seal is leaky and I don't suppose that anyone makes the shaft seals.
Thanks for any insight that you can provide.
Bill

[Joe L.]

Re: 1969 Vacuum actuator part numbers

Hi Gang,
It's been awhile since i've posted here. Still plugging away at restoring my 1969 Convertible 427/390 w/AC. The deeper I go the more I find I need to fix or replace. I need the GM part numbers for two vacuum actuators. The first one is in the box that the heater core sits in (selector assembly # 3949877). The other one is in the box that directs air up, down or both (distribution duct assembly # 3946979). Each of these actuators has two vacuum hoses going to them. They both leak on the shaft side of the actuator so the diaphragm is good but the shaft seal is leaky and I don't suppose that anyone makes the shaft seals.
Thanks for any insight that you can provide.
Bill

Bill------

The history of these actuators is very confused.

I believe the air inlet plenum valve actuator was originally GM #1998944. In July, 1977 this was superceded by GM #1996503 and in December 1980 GM #1996607 superceded it. The latter was discontinued without supercession in April, 1989.

I believe the heater valve distribution actuator was originally GM #1998961. This was discontinued and replaced by GM #1998990 in October, 1970. The latter was replaced by GM #1996505 in February, 1973 and that was replaced by GM #1996608 in July, 1983. 1996608 was discontinued without supercession in March, 1989.

Notwithstanding the above, it's also possible that GM #1996603 and, later, GM #1996686 might also be applicable to the heater air valve distributor actuator application. Both of those are also discontinued, though.

[William D.]

Re: 1969 Vacuum actuator part numbers

Thanks, Joe.
Will GM# 1998955 work in my 1969 as this was for all 1970-72 A/C and non A/C?
Bill

[Joe L.]

Re: 1969 Vacuum actuator part numbers

Thanks, Joe.
Will GM# 1998955 work in my 1969 as this was for all 1970-72 A/C and non A/C?
Bill

Bill-----


I cannot find that GM #1998955 was ever cataloged for a Corvette application. It's possible it was, though; as I mentioned, there's a lot of "confusion" regarding applicable actuators.

Might the 1998955 work even if it was never cataloged for the application? Yes, it might.

[William D.]

Re: 1969 Vacuum actuator part numbers

Joe,
It's in my 1973 parts catalog in group 9.786 # 1998955
Bill

[Dallas K.]

Re: 1969 Vacuum actuator part numbers

So does anyone reproduce or restore these actuators for 69, 70 non a/c heater boxes and the astro vents in the rear? Mine need diaphrams.

[Joe L.]

Re: 1969 Vacuum actuator part numbers

Joe,
It's in my 1973 parts catalog in group 9.786 # 1998955
Bill

Bill------


Yes, I see that now. However, I was looking for actuators for AC applications and it indicates 1998955 is for a NON-AC application.

[Don W.]

Re: 1969 Vacuum actuator part numbers

Dr Rebuild has these....Don

http://www.docrebuild.com/dr-r-web/ac-vac2.pdf

[Dallas K.]

Re: 1969 Vacuum actuator part numbers

They say they do not have these and will not be getting anymore in.

[William D.]

Re: 1969 Vacuum actuator part numbers

Am I interpreting the Parts book incorrectly? It says:
69 Corvette (exc. C.A.C.),
70-72 Corvette,
73 Corvette (exc. C.A.C.) .............. 1998955

With no exceptions listed for 70-72 doesn't it imply that this actuator is good for AC and non-AC applications?

Thanks for your input.
Bill

[Joe L.]

Re: 1969 Vacuum actuator part numbers

Am I interpreting the Parts book incorrectly? It says:
69 Corvette (exc. C.A.C.),
70-72 Corvette,
73 Corvette (exc. C.A.C.) .............. 1998955

With no exceptions listed for 70-72 doesn't it imply that this actuator is good for AC and non-AC applications?

Thanks for your input.
Bill

Bill------


Yes, that's exactly what it means for 1970-72. However, I thought your car was a 1969.

[William D.]

Re: 1969 Vacuum actuator part numbers

Joe,
My car is a 69 but I'm trying to find replacements for my defective actuators. How different can the 70, 71 or 72 part be? They all share the same distribution duct assembly (GM# 3946979) and blower evaporator aassembly (GM# 3949810) yet they have different selector assemblies (1969-GM# 3949877, 1970-GM# 3984658, 1971-GM# 3992143, 1972-GM# 6262674). How different can these selector assemblies be when they all bolt up to the same blower evaporator housing and use the same A/C control assembly (GM# 3942622 thru 1971 and then GM# 6262641 from 1972 on)? Very frustrating and confusing.
Bill

[Terry M.]

Re: 1969 Vacuum actuator part numbers

How different can these selector assemblies be when they all bolt up to the same blower evaporator housing and use the same A/C control assembly (GM# 3942622 thru 1971 and then GM# 6262641 from 1972 on)?
Bill

One of the differences between GM# 3942622 thru 1971 and then GM# 6262641 from 1972 on is the color of the lettering. The 622 is green letters and the 641 is white letters. I can't tell you this is the ONLY difference, but it is the most obvious to the judges.

[Dale G.]

Re: 1969 Vacuum actuator part numbers

Dallas is at work tonight and asked me to post these pictures of his original non-air heater actuators. Dallas is looking for replacements for these.

[William D.]

Re: 1969 Vacuum actuator part numbers

Hi Terry,
I think that is the only difference because this became the replacement for the earlier green letter version.
Bill