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76 AC plenam cleaning

THORIN

Well-known member
Joined
Nov 19, 2004
Messages
98
Location
Minneapolis
Corvette
1976 coupe
Old issue, its time to deal with it. I just took a long trip and my AC is not up to standards. It has been switched to R34 and is charged. It blows cold air but very weakly. It has been suggested that the AC plenam is full of 30 years worth of garbage and needs to be cleaned to let the air flow through like it should. So this weekend I want to get into it and clean it out. Never having done something like this are there any suggestions. In fact before I start tearing into one side or the other. Is it in the cockpit side or the engine side?
The other thing is I don't like that the box under the dash where the heater is, is always hot. I have been told I can instal a shutoff valve in the heater water hose. Will something bad happen if I do? Also should I do it on the inflow or outflow?
Thanks.
 

Artsvette73

Well-known member
Joined
Jan 24, 2004
Messages
174
Location
New Jersey
Corvette
1973 Silver coupe, 1977 L48
You only need to remove the inner half of the evap housing.
There is only one bolt on the inside pass floor area. The rest are on the outside.
If you have the efe valve on the exhaust manifold you will have to remove it. Disconnect the lines going to the evaporator and lift it out. Then take a look at the temp door see if it fully closes when you operate the control. If it doesn't fully close heat will mix with the a/c.
 

LVMYVT76

Well-known member
Joined
Apr 21, 2006
Messages
664
Location
springfield, mo
Corvette
1976 medium blue
There could many reasons for hot air coming in. In the engine compartment, check to see if there is a sealant where the housing pieces go together, if not get some black dum-dum from 3-m at auto parts store to seal this. It could also be the sealant where these housing parts seal against the fire wall. Also, the fresh air vent located on the passenger side may have the seals rotted off. this lets outside air in. The hood seal on the back of the hood needs to be good or else engine heat goes into the fresh air vent instead of cool air. The seals on the duct work under the dash could be gone and the air doesn't go through the ducts onto you body. Heat from under the car can be coming in, especially if you have hedders. I put a be cool mat under my carpet and tunnel. you could have a shut off valve bad or leaking past on the heater hose circuit. many other problems too.
 

THORIN

Well-known member
Joined
Nov 19, 2004
Messages
98
Location
Minneapolis
Corvette
1976 coupe
Tommorrow I will get into it and see what happens. I'll let you know.
 

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