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Topic: Defroster

in Forum: C3 Cooling and Heating Systems


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Defroster (1/8)
 3/12/08 8:11am
terntes
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Little Rock, AR - USA

Vette(s):
1982 Collector Edition


Joined: 7/10/2007
Posts: 123

My defroster selection will only blow for a couple of moments, perhaps 10 seconds, then the air flow diverts to the floor as the heater. The fan works well, the AC selection works well. Is there a vacuum accumulator or diaphram somewhere under the dash or a weak seal somewhere?
terntes
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Defroster (2/8)
 3/12/08 8:21am
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
Posts: 20126

Sounds like a vacuum problem for sure. I'd lean towards the actual selector(the lever that changes the modes), in the center console, as the culprit. It is basically a vacuum "router" that determines where the vac. supply goes. They have a tendency to dry out over time, and start leaking a little vac. The "default" mode is Defrost, so something is telling the mode door to switch to heat. Prolly a leak in the selector switch.

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Defroster (3/8)
 3/16/08 7:17am
terntes
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Little Rock, AR - USA

Vette(s):
1982 Collector Edition


Joined: 7/10/2007
Posts: 123

I'm late in a reply, I've been working on wheels, brakes, and replacing the one size fits all (but not mine) replaced after market cable for the hot/cold selection. I've inspected the router, a vinyl or urethane device it seems. It looks to be in good condition, but I definitely here an air noise up in the dash area, seems to be behind the radio, when I move the selector from defrost to heat to vent. In AC mode the sound disappears. I was wondering if there is an accumulator or vacuum actuator somewhere I can't see.

terntes
Defroster (4/8)
 3/17/08 1:06pm
VetteSpecialties
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Mounds View, MN - USA

Vette(s):
70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe


Joined: 5/24/2007
Posts: 1031

I've heard that noise!  There is one of those cute little vacuum actuators hidden between the heater box and the firewall.  You only have to remove most of the heater to get to it.  They cost about $50.00 plus ten hours of your time.  But you might be lucky and find it is easier to get to.

Larry
Defroster (5/8)
 3/17/08 2:22pm
crossfire1982
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Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion


Joined: 8/22/2006
Posts: 1094

Terrence, The vacuum actuator behind the radio is going to be REALLY difficult to get to and I hope you dont have to go that route.  Before you do, check the vacuum hose that feeds the heater / defroster selector.  This hose goes through the firewall about  in the center.  It gets its vacuum at a "T" connection near the headlight vacuum line one way valve. near the brake booster.  Check the vacuum connections.  I had a very similar problem and found that I had cracked  the 25 year old plastic "T" whle replacing the one way valve to my healight system.  I hope its as simple as that.
Defroster (6/8)
 3/18/08 4:26am
terntes
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Little Rock, AR - USA

Vette(s):
1982 Collector Edition


Joined: 7/10/2007
Posts: 123

Crossfire,
  I've checked the "T", everything is pretty good there. I do have a small issue at the firewall port but the noise I hear is definitely behind the radio area and only is noticeable inside the car while moving the selector in the heat/defrost selection area. I was hoping it was normal, but I don't think so. I can see a black hose going up there somewhere but everything is so tight and so many wires I can't really tell. I'll have to take the seat out (again) and go exploring.
terntes
Defroster (7/8)
 3/18/08 7:08am
crossfire1982
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Cramerton, NC - USA

Vette(s):
black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion


Joined: 8/22/2006
Posts: 1094

I was hoping that would be an easy fix.. I lucked out on mine but had already located the vacuum actuator and was trying to figure out how to get to it when I found my vacuum leak under the hood... good luck getting to it and let us know how difficult it is.
Defroster (8/8)
 3/21/08 11:07pm
aceintheholeLifetime Member
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Manteca, CA - USA

Vette(s):
1978,two tone,Metalic Rootbeer & gold 1975 L48 4 speed


Joined: 11/20/2005
Posts: 3623

Seriously ! I'm hearing the same noise on the wifes '78. I've always known it's a vacuum leak, but the car runs so good, it's easy to forget. I'm sure it's worth going in after "someday". We'd appreciate your sharing of your experience. I love doing these projects, but I'm glad I don't have to do it for a living.Confused At least, not on new cars.

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Jimmy B.
Just can't wait to get on the road again.

 
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