No Heat Getting Chilly Outside

My 68 Skylark has no heat at all . Recently went through HVAC system after dashboard resto and addressed the following. Removed , cleaned control unit ( original A/C car ) , all vacuum lines inspected and changed where needed , blower switch-wiring- resistor plug changed . All 4 blower speeds work and likewise all the ductwork/hoses was gone through and replaced as needed . Heater core was back flushed ( very dirty now clean ) . New heat/ defrost cables from Old Air were installed with limited success. Heat cable was straightforward but blue defrost cable is too long making it impossible to connect to defrost door . The defrost and heater doors do move freely when manually opened. The vacuum switch on the fan speed switch was also changed. Car was purchased a few hrs ago but the wiring/ vacuum lines were a mess . Because of this the HVAC system never worked . Heater control valve was leaking and changed when purchased. Currently with heat door wide open in heat position I have no heat . The incoming heater hose is decently “ warm “ the return is cold . Radiator is full with new 160 thermostat. Thought I went though everything but I’m missing something. As always any and all opinions welcomed.

 

Sounds like your control valve is not opening. It operates off vacuum solenoid. That’s the way my 69 operates

 

I applied 30 lbs of vacuum to the HCV It did get warmer but did not result in heat . This nasty stuff came out of my heater core

 

Run a straight hose from heater core to intake, eliminating control valve. See if you get heat.

 

I’m at work with the car and that’s my lunch time project . Off hand do know the size of the fitting that goes into manifold where the HCV is located ?

 

Was curious Brett, all of that crap came out initially when I turned on the hose . In 5 minutes it was crystal clear with no leaks . Do you think it is necessary to replace the heater core ? Can there still be blockages in it ?

 

Was it leaking on your pass side carpet, or steaming up your windows on the inside? That's the time for replacement imo.

 

Owned car 6 yrs purchased from original owner_- southern car , like I said the fan switch wiring was a disaster and most of the 7-8 vacuum lines were cracked from age . Both control cables were broken. Amazingly when I got it home ; when I removed the a/c lines while detailing the engine , a full charge of R 12 escaped into the air. I immediately closed it back up and noticed the compressor moved freely - all good signs. That’s for another day .Just got it back on the road after 3 yr mini restoration and otherwise looks very good ( not perfect) and is a pleasure drive . HVAC system has never worked since I owned the car and with first cold weather here now the heat is first up . Changing the core if it has to be done is will be , but seemed to be cleaned out when flushed with no ill effects .

 

Make sure you have the correct control valve. Some open with vacuum, some close with vacuum. They look the same on the outside. As said above, bypass it and see what happens.

 

⬆️⬆️⬆️Yep, wrong control valve will not open.

 

Going to try bypassing the valve tonight. For what it’s worth is there a tell the difference between the 2 types of valves ?

 

Also check your timing. If it is way too advanced, the engine will never get warm enough for the heater to work.

 

Just went through the timing- was running too hot . New vacuum advance and changed distributor springs car is running better than it ever did . Going to bypass the heater control valve tomorrow and eliminate that possibility. Will update tomorrow

 

Blow through the valve with no vacuum and then with vacuum. Of course it has to be off the car...

 

Bill you mean with compressed air Blow it through the vacuum port ?

 

No - blow through the water port. That will tell you if it is open. I just use my lungs. Test it with and without vacuum.

 

Found the problem - no vacuum to the HCV . Took the valve off , cleaned it up And noted when I applied vacuum to the port on it the valve was moving . I plumbed into the manifold some 3/8 black pipe with an adapter to my heater hose & like that 85 degree heat . The last issue is to solve is how to hook up the defroster door cable. The heater door ( red ) cable is a PITA - to put it mildly, to connect to the control unit. The defrost door cable ( blue ) as I see it can’t be done. The distance from where the cable attaches to the door is 8” The cable I have from Old Air is 30” . Called the company to verify cable is correct for 68 Skylark w/ A/C and was told it was . Interesting No one in the technical dept had any insights into installing it . 1968 HVAC controls was a one and done bad idea as most 68 owners will attest to . If any one has any thoughts on or has done this cable install would like to hear them .

 

One trick to working under the dash is to pull the seat out. Then you can lay down on your back and reach everything.