Check your blower motor resistor, it might be burnt out.

 

The reason I'm critical of this topic post is that I worked on these cars for GM when they were brand new. There was not a cabin heat problem with the Corvettes built through the '70s: They were nice, tight cars that did not leak hot air, water, or anything else. The blower safety system worked great, and it drew in fresh outside air without heating it up.

These cars are now 40 years old, and instead of working on new Vettes, I'm now restoring the cars I was working on when they came off the showroom floor. Over these 40 years, every foam seal in these cars has turned to crusty crap and dust, and these cars are now leaky antiques. Every C2 and C3 that I have torn down has had leaking or non-existant seals in the heater box and in the flapper doors controlling heat settings and hot air mixing. They also have bad seals in the firewall area sealing the A/C or heater box against the engine compartment, as well as leaking/damaged/missing firewall penetration seals & grommets. Insulation matts are often missing or damaged, both on the inside of the firewall, and under the tranny tunnel.

I have found that once the actual problems are correctly repaired, there is no cabin heat soak problem: the cars are as comfortable as they were when they were new. Fixing a problem by ignoring the actual problem and creating another problem is just a really bad way to "fix" a car. Right up there with bailing wire and duct tape.

If you choose to be involved with these half-century old cars, then at least fix 'em right...

Lars

 

 

Here is my solution:



I bent down the tab for the yellow wire on the resistor. That did the trick. The tab could easily be bent back up again. I checked the operation with a voltmeter and that is the wire that provides power to the blower with the key in the on position.

Here is a list of all the other cabin heat/A-C things I have done to the car:

* Shut off valve on heater core line
* Hushmat and reflectix on firewall, tranny tunnel and floor.
* New tranny tunnel foam collar
* New rubber shifter boot.
* Sealed all holes in the firewall with RTV.
* New speedo grommet
* New hood seal
* Tweaked the fit of the cowl fresh air door
* New seal on passenger footwell fresh air door.
* New shifter rod boot. Old one was shreaded.
* New seal around M/C. Old one was in pieces.
* Pro6ten compressor
* Parallel flow condenser
* VIR elminator
* New rubber and steel lines
* New blower with C4 squirel cage fan and 0.75" spacer
* Insulation on outside of A/C box.
* New seals on engine side of A/C box
* New seals for cabin side of A/C box.
* New seals on ducts/vents/*****
* New drain tube under A/C box.
* New blower motor relay.
* New blower motor resistor
* New heater core

On my recent Bowling Green trip, while driving at 70mph and with the AC off and windows down I could still feel a trickle of hot air coming through the vents. After an hour or so the center vent housing was very hot. My goal with this car is to make it comfortable to drive in any condition.

 

Here are some pages I saved when I looked into this topic.
http://www.corvetteactioncenter.com/...et-update.html
http://home.comcast.net/~chadwick.ro...entilation.htm
http://forums.corvetteforum.com/c3-t...abin-heat.html

 

After replacing ALL of the worn out air seals and installing proper insulation, my car is as comfortable as a new car now. Removing the low blower air is not a wise move. If bubba had left my car alone, it would have been a lot easier to get back to normal. Have your family let us know if you get sick or die.

Good luck!

 

Wow.....

 

How else are we going to know it was worth it?

 

I have been following the comments about the safety issue and finally thought that I had to add my 2 cents on this issue. A few thoughts:

1. "Flow through ventilation" was more a marketing ploy than a safety issue, which is just a side benefit of having air blown into the cabinet at all times.
2. I have had my blower discounted from blowing air into the cabin all the time for about 25 years and have never had an issue with carbon monoxide poisoning-still here!
3. There is not one car I currently own that continuously blows air into the cabin when the blower is in the off position-2010 Z06, 1994 Mustang GT, 2001 Grand Prix etc.
4. Nothing like having the blower motor run all the time to wear out the blower motor prematurely.
5. If you are worried about carbon monoxide poisoning , crack the driver's window when you are driving the car for fresh air.
6. Disconnect the blower motor from running all the time immensely helps with the hot air issue in the cabins of C3's

With all due respect, Complete nonsense!

 

This is a tough problem to fix. even if you put gate valves on both heater core hoses,new cowl seal, block off wiper tray vents you still get convection air heat coming into the cabin. I havent tried unhooking the blower motor but I dont think it will do any good. the plenum or heater core box needs to be insulated and sealed. Thats difficult to do
because you cant get to it. My 79 is still like an oven inside in hot weather and smelling exhaust fumes. I dont know what else to do because I dont want to tear it all apart. I think the only other thing that can be done is replace the compressor and accumulator and get the air going again. but I dont know what to do about the fumes

 

Lars,
just curious when did GM start the continous fan feature in C-3's?
Would my '68 BB w/ A/C have had it?
Thanks,
MArshal

 

Doubtful, my '72 never had it....course mine is a rag top, and as such leaks like krazy anyway, I sealed the flapper for the fresh air intake, and so it's on permanent recirc....put in a C4 blower and spacer for better airflow, but the down side is, using that damn r134 in the a/c has reduced the air to maybe a 20f drop across the coil, where they used to blow frost out the vents....

I have been trying to find a parallel flow condenser for my car, but it looks like junkyard is going to have to be the solution, I"m told it has to be a newer condenser or 134 will not work good....so far, no luck....

 

[QUOTE=jcloving;1580726189]Here is my solution:




Excellent job. Thanks for the post.

Fear of dying because of this "fix" is the least of my concerns. (I have enough suction from my Closed windows to rip your shirt off at highway speeds)


(Though they usually have good advice and mean well, many "experts" have yet to figure out how to post responses without the smack of arrogance.)

Thanks again!!!