Ford Muscle Cars Tech Forum banner
1 - 20 of 40 Posts

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #1 · (Edited)
I made the original post sometime ago before the forum buyout and reformatting. All the original pictures were deleted which makes the post darn near impossible to use. Since winter is here this may be helpful to someone with a 3rd generation full size with factory air diagnose and repair their heat function. With that I have the pictures and this is copy of the original more or less.

Hello all,

Seemed like a good time of the year to share what I did to overhaul the heater portion of the Ford HVAC system. Maybe it can help someone else out with little or no heat.

So no doubt, those with factory air con systems have come across a problem with the HVAC system as a whole, either little to no heat or no air con.

The system on these is a little odd in that it was overly complicated for what it did and still doesn't allow for dehumidified warm air to the windscreen (defrost).

These systems unlike the heat only option do not have a mechanical blend door, instead the temperature of the heater core and evaporator itself is modulated to your hot-cold setting.

To start, you have to have a good source of vacuum. The engine needs to at least have 15" of vacuum to fully open the heater coolant valve. Stock engines should have no problem with this.

Given the small diameter of the hoses it only takes a small leak and the whole system can be affected.

I found vacuum leaks on my reservoir can itself, especially at the top.

167232


The best way I found was to thoroughly clean it (carb spray works just fine too) to wash grease and muck off it. Then using a small vacuum hand pump apply a small vacuum and allow the leak to gently pull in the sealant (RTV) but no to hard to where the leak reappears.

The next thing to check for is a check valve in the supply. Some say it's in the top part of the vacuum reservoir while some literature shows a separate valve inline to the reservoir. I probed around on this one and there was no evidence of anything in the top port, no spring or disc. Either it was never there or it disintegrated.

167233


If your tank doesn't have a check valve in it or it doesn't seal well. I found this one at Napa.

167234


Once that the vacuum reservoir and supply are checked out and working properly, next to check the remainder of the system.

Old hoses turn hard and leak and if yours are questionable I'd replace them. I know there's a lot under the dash and in the engine bay.

The next place to check is the heater coolant/control valve itself. Usually the ancient seal will start to leak or it will corrode to the point it will no longer move, or the diaphragm will rupture/tear/crack/leak.

167235


This one wouldn't budge. Problem is these are not reproduced exactly to fit. There are generic ones that will work.

167246


But the original mounting bracket take a little modification to hold the new part. I need to mention there are two flavors of heater valves. One that is normally open and one that is normally closed. Our gals need the one that's normally closed, which is the uncommon one.

Here's the modification I did to the bracket to hold the newer valve.

167236


167237


167238


167241


167239



For the retaining screw, I ground it to a dull point at the end which dimples the valve behind the plunger, but since the plunger has a small travel this does not interfere with it and so it seals tight with no vacuum and it's very open when vacuum is applied.

continued in next post.
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #2 ·
Heater continued

Next is checking the heater vacuum thermostat.

167242


With the thermostat set to the cold position there should be a vacuum leak (vacuum bleed off) if checking from the heater valve control port. If checking from the vacuum supply side it should hold vacuum when set to full cold.

167243


Next set the thermostat to full heat and plug the port to the heater control valve and pull vacuum on the supply port. It should hold vacuum.

If it doesn't hold vacuum especially in the last test, the thermostat is dirty or has a ruptured diaphragm. It can be taken apart, but there are two small needle and seats (valves) in there. The needle is the size of a hemming needle. It's almost analogous to working on a wrist watch as far as delicacy is concerned.

I had pictures of taking this apart, cleaning and inspecting and reassembling. I lost those pics. But I still have 3 more of these Ford HVAC systems to R&R so hopefully in the future I can cover this better.

If you're confident in taking it apart go for it, if not, occasionally I see these NOS on EBay for 100-250 dollars. Something to keep in mind.

Lastly you want to make sure the Bowden cable that connects from the dash 'hot-cold' selector is adjusted properly to the cooling and heating thermostats under that plastic cover in the engine bay.

167244


Another quick check to make sure you have enough vacuum at the heating thermostat is to check the vacuum servo motor here in the picture on the right. With the engine running in the heat or defrost positions it should have pulled in its arm hard. If it's not pulled in or not pulled in all the way and fully seated then you need to recheck the vacuum lines and the HVAC selector on the dash for vacuum leaks.

And please it kind of goes without saying to check that the heater core itself isn't full of scale or plugged or the 90' heater hose elbow on top of the engine isn't plugged as well.

Hope that helps solve heat problems.

Cheers..
 

·
Registered
Joined
·
12 Posts
Are the vacuum hose colors hooked to the dash control unit just as they are shown on your A/C-Heater vacuum circuit photo ?
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #4 ·
Are the vacuum hose colors hooked to the dash control unit just as they are shown on your A/C-Heater vacuum circuit photo ?
Hello wldavis,

Yuppers they are. The reason especially why the heater related vacuum hoses are connected to the dash control unit is that in cooling mode the vacuum is shut off to the heater mode door vacuum servo, heater thermostat, and subsequently coolant control valve.

Cheers
 

·
Registered
Joined
·
12 Posts
Thank you. Can i send some photos to you via email or text or ???? or should I just post them here ??? This thread has been very helpful. I am at the heater vacuum thermostat now in my troubleshooting or why I have no heat. This is my next point to check into. From your description, it looks like it will be fun !!!!
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #7 ·
Thank you. Can i send some photos to you via email or text or ???? or should I just post them here ??? This thread has been very helpful. I am at the heater vacuum thermostat now in my troubleshooting or why I have no heat. This is my next point to check into. From your description, it looks like it will be fun !!!!
Hello wldavis,

Just PM me here and I'll send you my private email.

Cheers
 

·
Registered
Joined
·
12 Posts
I do not know if this correct, but this is what the one-way vacuum valve looks like on my 65 Ford Custom with factory A/C. The valve is plumbed between the engine intake manifold and
the vacuum supply tank. -William
Metal Baggage Steel Synthetic rubber
 

·
Premium Member
Joined
·
6,101 Posts
I don't want to derail this thread but I have a question about vacuum check valves. Like the one on the canister, why is it needed?
 

·
Premium Member
Joined
·
6,101 Posts
Duplicate
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #11 ·
I do not know if this correct, but this is what the one-way vacuum valve looks like on my 65 Ford Custom with factory A/C. The valve is plumbed between the engine intake manifold and
the vacuum supply tank. -William View attachment 167256
Hello wldavis,

That would be correct according to not only the Ford drawing but my own empirical experience with these systems. I have enough parts for 4 additional systems plus the one I finished on the LTD. Every single vacuum reservior I checked either had a disintegrated check valve or there simply is no check valve in it to begin with and you need the external.

If someone has positive proof of a check valve in a 3rd gen full size factory original vacuum can I'd love to hear about it.

Cheers

p.s. I received your PM and I replied with my personal email.
 

·
Premium Member
Joined
·
616 Posts
DesertXL.

Thanks for updating this with the pictures. I hated the re-formatting of this and also the great photobucket photo delete. Those messed up alot of posts like this with good information.
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #13 ·
DesertXL.

Thanks for updating this with the pictures. I hated the re-formatting of this and also the great photobucket photo delete. Those messed up alot of posts like this with good information.
Hiyah fried_daddy,

Long time no hear. How have you been? What have you been up to?

You're welcome for the repost. I know these systems are overcomplicated for a newbee to them. I spent a good deal of time learning all I could about them. If I can help someone else with these all the better :)

Cheers
 

·
Registered
Joined
·
12 Posts
I don't want to derail this thread but I have a question about vacuum check valves. Like the one on the canister, why is it needed?
Puttster,
It is my belief that a check valve is needed in the canister in order to hold vacuum on the system should vacuum from the engine "fall off", like going up a long incline, etc.
Maybe it is just "extra protection" to back up the one-way valve that is plumbed into the system between the engine intake manifold and the vacuum canister The check
valve in the canister will also hold vacuum on the system - for awhile - after the engine is turned off.
 

·
Premium Member
Joined
·
6,101 Posts
My old 53 buick needed a canister. It didn't have one and every time you'd step on the gas the windshield wipers and the wolf whistle wouldn't work.
Fast forward 12 years to my 1965 Galaxie with all these newfangled electric gadgets. Seems like leaving vacuum in the system after the engine shuts off will only add stress to the diaphragms. But that's just me vs 1,000 Ford engineers.
 

·
Registered
Joined
·
4 Posts
Heater continued

Next is checking the heater vacuum thermostat.

View attachment 167242

With the thermostat set to the cold position there should be a vacuum leak (vacuum bleed off) if checking from the heater valve control port. If checking from the vacuum supply side it should hold vacuum when set to full cold.

View attachment 167243

Next set the thermostat to full heat and plug the port to the heater control valve and pull vacuum on the supply port. It should hold vacuum.

If it doesn't hold vacuum especially in the last test, the thermostat is dirty or has a ruptured diaphragm. It can be taken apart, but there are two small needle and seats (valves) in there. The needle is the size of a hemming needle. It's almost analogous to working on a wrist watch as far as delicacy is concerned.

I had pictures of taking this apart, cleaning and inspecting and reassembling. I lost those pics. But I still have 3 more of these Ford HVAC systems to R&R so hopefully in the future I can cover this better.

If you're confident in taking it apart go for it, if not, occasionally I see these NOS on EBay for 100-250 dollars. Something to keep in mind.

Lastly you want to make sure the Bowden cable that connects from the dash 'hot-cold' selector is adjusted properly to the cooling and heating thermostats under that plastic cover in the engine bay.

View attachment 167244

Another quick check to make sure you have enough vacuum at the heating thermostat is to check the vacuum servo motor here in the picture on the right. With the engine running in the heat or defrost positions it should have pulled in its arm hard. If it's not pulled in or not pulled in all the way and fully seated then you need to recheck the vacuum lines and the HVAC selector on the dash for vacuum leaks.

And please it kind of goes without saying to check that the heater core itself isn't full of scale or plugged or the 90' heater hose elbow on top of the engine isn't plugged as well.

Hope that helps solve heat problems.

Cheers..
thank you for providing this info, great resource, i am currently rebuilding the AC system in my 65 galaxie. can you provide any thoughts on where the blower circuit breaker is located? Thanks!
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #17 ·
thank you for providing this info, great resource, i am currently rebuilding the AC system in my 65 galaxie. can you provide any thoughts on where the blower circuit breaker is located? Thanks!
Hello Ed Galford,

You're quite welcome on the information. Happy to help.

The circuit breaker for the heater blower and compressor clutch is located on the back of the ignition switch for factory air conditioning. It's just an add on to the centre screw stud on the back of the switch.

Good luck with your HVAC rebuild, these aren't the easiest to refurbish.

Cheers
 

·
Registered
Joined
·
4 Posts
Hello Ed Galford,

You're quite welcome on the information. Happy to help.

The circuit breaker for the heater blower and compressor clutch is located on the back of the ignition switch for factory air conditioning. It's just an add on to the centre screw stud on the back of the switch.

Good luck with your HVAC rebuild, these aren't the easiest to refurbish.

Cheers
thanks for the quick reply! i looked and do not have that on the switch, what is the amp rating? i can find those at a a parts store, thanks again!
 

·
Registered
Joined
·
1,765 Posts
Discussion Starter · #19 ·
thanks for the quick reply! i looked and do not have that on the switch, what is the amp rating? i can find those at a a parts store, thanks again!
Hello Ed Galford,

You're welcome.

I do believe it's a 30 amp circuit breaker because it also supplies the clutch as well as the blower motor. You can find 30 amp circuit breakers but you will probably have to do some modification as you won't find the exact replacement with the eyelet on it, but you may get lucky.

Chances are you'll have to use a 10 gauge ATO style inline fuse holder and use the ATO 30 amp circuit breaker and crimp/solder a ring terminal to one end of the fuse holder and attach that to the ignition switch centre terminal and then the other end crimped/soldered into the original feed wire that goes to the blower switch.

Cheers

P.S. please feel free to post your rebuilding pictures of the HVAC system.
 

·
Premium Member
Joined
·
616 Posts
Hiyah fried_daddy,

Long time no hear. How have you been? What have you been up to?

You're welcome for the repost. I know these systems are overcomplicated for a newbee to them. I spent a good deal of time learning all I could about them. If I can help someone else with these all the better :)

Cheers
Been doing great here. Not much Galaxie activity due to corona but I will be glad when the cruise ins start back. Hope 2021 will make it happen. I do need to get some HVAC going since i'm back in this southern heat. Thanks for the post again.
 
1 - 20 of 40 Posts
Top