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I was reading past threads about the blower not working in 79 corvettes. My system is fully charged and I have taken the glove box out to see the cable with the plunger. When I directed the cable to cold it does not push down the plunger. So I tried pushing the plunger down with my finger to see if cold air would come out and it does not. When I push the lever to hot or vent, it does however turn the heat on in the vent on that it will not let the cold air come into the car? I have put a brand new pallenium in as well .My next step is I'm going to adjust the cable so that it pushes down the plunger but would it not have let the cold air through when I did it manually with my finger? I've checked all three vacuum lines and they are getting sufficient suction under the hood and I don't see any cracks. Where should I go from here?
Last edited by Slick1966; Dec 1, 2022 at 08:40 PM.
That switch behind glove box only sends vacuum to hot water shut off switch on one heater hose.
please clarify what the complaint is? You want cold air? Ac on?
is compressor running? what do the gauges say?
history of ac? did it work ever? did you recharge it? do you know what is in it?
and what is this? I have put a brand new pallenium in as well
Hello and thank you for your help. Yes the AC is charged proper pressure brand new compressor and dryer. It did work before the last guy put the compressor in but only would blow cold on low but ever since he put the new compressor and dryer in no cold air is coming out of the vents. The actuator on the passenger side that you reach from under the hood behind the wheel well by the door was unplugged at the time but is now connected to the correct vacuum. So basically everything is running and charged correctly but no cold air is coming out the vent.
Does it blow cold at all upon startup and gradually warm up as the motor warms up?
That's what my black 79 did till I realized the heater shutoff valve in the heater hose was stuck open with corrosion.
Replaced the valve and hoses, cold air again.
Make sure the control lever is ON cold. Not close but ON.
Also, simple adjustment for the lever/button at the heater box .... one of those little rubber caps you might see on wire shelving in your closets.
That's how I adjusted mine.
edit. I see you have the early plunger with the big head. My rubber cap fix won't work for that, only the small head.
well... you need to see if ac on the compressor engages.. and you really need gauges to see what's going on.. i would re visit the last guy..
are you able to DIY? this forum can guide you through if you are have tools..
alos take planty pics.
important to know if compressor engaging..
Hello, no cold air at all. I have the glove box removed and I can see the plunger with the cable with the cold lever directly on cold the plunger is definitely not compressed the pressure in the AC line is correct and the compressor is definitely engaging and clicking on so everything is working properly just no cold air coming out. I keep reading about adjusting the cable so that it closes the plunger but no one has stated how far the plunger should close? When I push the lever over it does not touch it by about a half inch so there is absolutely no depression of the plunger at all.p
Hello, no cold air at all. I have the glove box removed and I can see the plunger with the cable with the cold lever directly on cold the plunger is definitely not compressed the pressure in the AC line is correct and the compressor is definitely engaging and clicking on so everything is working properly just no cold air coming out. I keep reading about adjusting the cable so that it closes the plunger but no one has stated how far the plunger should close? When I push the lever over it does not touch it by about a half inch so there is absolutely no depression of the plunger at all.p
There is no set depth on how far the plunger should travel, the vacuum switch either sends a vacuum signal or it doesn't.
Cut a wedge from whatever handy so the hot water shutoff vacuum valve button is depressed.
Set the slider function lever to AC MAX fan speed switch to High Speed and try again...
FYI, looking at your hot water vacuum switch you have a early build 1979...Those vacuum switches are available through various vendors, late 79-82 vacuum switches are harder to find...
It may also be the cable is just stretched and there is just no adjustment left.
You could always remove the vacuum switch and with a round file slot the existing holes so when adjusted the switch sits closer to the arm..
you moved the door and were able to send hot air by the lever. and assume at startup you still have issue.. the shut off valve is not your issue.. IMO.
so compressor running non stop? or cycling?
Did you put gauges on to confirm? (you can rent them for free) and see what they are doing when running.
is the accumulator cold like the pipe entering the evaporator?
Am I supposed to adjust the two screws on the base or the single screw on the cable? Also upon removing the cable to adjust it I am looking at the plunger is there supposed to be three vacuum lines attached to it? Empty space in the front or is that just for air? And see
the picture
There is a black vacuum line going to where is marked white, and there is a white vacuum line going to where it is marked red right next to that is another spot right above the plunger that is empty with no line. If there is a line that is supposed to be attached to that where would it be coming from?
There is a black vacuum line going to where is marked white, and there is a white vacuum line going to where it is marked red right next to that is another spot right above the plunger that is empty with no line. If there is a line that is supposed to be attached to that where would it be coming from?
THINK I FOUND IT . Hard to see but the rubber grommet coming through the firewall has the three vacuum lines everybody's been telling me about the bottom vacuum line white is missing where would that vacuum line go to this is probably the problem hopefully.
1979 Corvette blowing cold problem
