What to Replace when Redoing interior HVAC components?

[Henrius]

Finally got the dash halfway disassembled in my 1965, and found the severed vacuum line that fed to the control block and kept everything from working.

While I am in there, I am going to buy a vacuum gun (any suggestions on which one?) and test operation of all the plenum door vacuum actuators.

BUT, while I am in there, should I replace:

1. Fan switch, even it is working now?
2. Vacuum control block?
3. ALL of vacuum lines? Hate to do this, as they are color coded. Is there any more durable modern hose material?

Hate to replace parts that work, but I really don't want to go into the dash again anytime soon.

Can't seem to find any sources that sell new or rebuilt MOPAR HVAC parts- only guys who sell complete systems for cars that never had A/C. Used to be a guy that rebuilt OEM parts, but cannot find him now. Anyone got any sources for that?

 

[Big_John]

BUT, while I am in there, should I replace:

1. Fan switch, even it is working now?
2. Vacuum control block?
3. ALL of vacuum lines? Hate to do this, as they are color coded. Is there any more durable modern hose material?

IMHO...

If it's working, leave it alone. Any "new" reproduction stuff isn't going to be as good. NOS should be better in theory, but realistically NOS stuff is sometimes an expensive crap shoot. If the hoses are still pliable, they will probably last longer than new ones.

 

[bigmoparjeff]

You can use an ohm meter to test the electrical side of the switches first. Ideally, you want to see zero ohms, but anything over 0.3 ohms and they need to be repaired. If the mode buttons on the selector switch are real stiff, it should come apart to be cleaned and lubed. There may be a thread somewhere on this site detailing how to do that. Do not try to remove the vacuum connection from the mode switch unless it tests bad or is too stiff. It's very common for the fragile vacuum ports to break off the back of the switch when you try to remove the vacuum lines. In that case, you'll need to buy an NOS switch for around $150. I've never worked on a '65, but the '66-'68 cars have another connection for the vacuum lines about 6 inches away from the switch that can safely taken apart.

I know that there are companies that do complete restorations of the hvac boxes. The '65-'68 C body unit is very similar to the '68-'70 B body unit, with the exception of the internal water valve used in the C bodies.

The biggest problem will be if you find any bad vacuum motors. Replacements are difficult to find these days and expensive when you do. I don't know if there is anyone out there that can repair them. I also haven't checked to see if anyone is making new ones for the B bodies with A/C.

You certainly want to look everything over real good for any signs of coolant leakage and I would also refurbish the blower motor while you have it out. Be sure to go over all the wiring and connectors looking for overheated or corroded terminals.

I can't remember if the '65-'68 boxes used any foam rubber to seal the air doors or case halves. Usually that foam starts to turn to dust over time and needs to be replaced. Detroit Muscle Technologies would likely have a foam kit for these if needed. It's been so long since I had one apart that I can't remember all the details. I recently refurbished the hvac system on a 1963 Chevy Impala with factory air and I could buy a foam kit that did the external seals but had to buy various shapes and sizes of foam rubber from McMaster-Carr to replace all the seals inside the distribution box and evaporator case.

As John said, those vacuum lines with the color stripes on them generally last forever, and will likely outlive any of the new garbage rubber hoses that are available today.


Jeff

 

[live4theking]

You can always plug the hose and use the vacuum gun to make sure it will hold. You will need seals from DMT. If you're replacing the heater core or the "h" valve pressure check the before installing. I pull the seats and carpet when doing this job.

 

[Henrius]

You can always plug the hose and use the vacuum gun to make sure it will hold. You will need seals from DMT. If you're replacing the heater core or the "h" valve pressure check the before installing. I pull the seats and carpet when doing this job.

Thanks. I looked up "vacuum gun" and the ones I found on the internet were for sucking liquid out of tight places. Can you give me a name and model of a vacuum gun meant to test car vacuum operated devices?

 

[Big_John]

Can you give me a name and model of a vacuum gun meant to test car vacuum operated devices?

There are cheaper ones, but this piece has been around for many years. https://www.harborfreight.com/mityvac-vacuum-pump-39522.html

I have one, I think I bought it before Harbor Freight started selling them. It's a decent tool and very useful to bleed brakes too.

 

[Justin Plant]

Mity Vac sell some good tools as well.

 

[volksworld]

I used HF's Pittsburg branded one...it was half the price of the MiteyVac. worked fine for the actuators...for the whole system I did what the FSM recommended...made a setup with a gauge and a bleed valve, hooked it to my A/C vacuum pump...the bleed valve let me limit the vacuum to 8 lbs ...had the controls and the entire box on the bench and was able to hit each button and make sure everything did what it was supposed to do

 

[Fury1969WI]

DMT has a kit for gaskets, etc. I would consider opening up and going through things and adding new gaskets. Just my opinion.

Mopar C Body 65-68 AC Heater Box Rebuild Restoration Seal Gasket Kit