AC, but no heat......

[r8rs4lf]

Factory AC '72

AC works, but heater does not.

The lever for heat does not stay to the right. I feel some type of detent when pushing it right like it wants to stay, but eventually moves towards the middle. That seems like an adjustment issue. Fan works on low, medium, and high.

I can get some pics up tomorrow, but what should I be looking for? Truck has an aftermarket aluminum radiator with twin fans, a newer condenser with an added switch controlled fan.

Kind of weird that AC works, but not heater.

Also, when I turn the fan on, I hear some things, maybe leaves moving inside that box down by the floor. I feel like I need to take that apart and clean it out. I will say when I first got the truck and turned on the fan, I noticed like 3-4 leaves among other debris on the truck floor.

Can anyone offer any help?

[Hook'em]

I'm no expert, but have been chasing heater and a/c issues in my '69 for 20 years or so. Since the experts haven't weighted in, I'll drop my thoughts.

If you aren't feeling any heated air at all, it doesn't sound like hot water is running through the heater core. There is a vacuum controlled heater valve that diverts hot water into the heater core. The vacuum line runs from the back of the control panel, through the firewall, and into the heater valve in the engine compartment. That would be the first thing I would check.

If the air is heating some, then there might be an issue with the diverter which switches between cold and hot. This diverter is controlled by the lever on the control panel.

There might be a few leaves or a bunch of leaves in the heater box.

You can do a search on the site for more information concerning these issues.

[HO455]

There is a good thread on rebuilding or restoring the AC heater box. Lots of photos in the thread. It should help you visualize what Hook'em is describing. Worth searching for.

[dmjlambert]

You can have a look at my thread and I'm sure there are a lot of others. In my thread I show the problems I had with the blend door. The system was full of rats nests and leaves and pecans that rats hauled in there to the duct works. Take it apart and clean it out. For working A/C I would advise do not open the A/C lines under the hood, use it until it actually stops cooling. No heat at all may mean you have no coolant frlowing through the heater core, which is inside the cab in a box at the passenger's feet. https://www.67-72chevytrucks.com/vbo...d.php?t=790246

[r8rs4lf]

Originally Posted by Hook'em

I'm no expert, but have been chasing heater and a/c issues in my '69 for 20 years or so. Since the experts haven't weighted in, I'll drop my thoughts.

If you aren't feeling any heated air at all, it doesn't sound like hot water is running through the heater core. There is a vacuum controlled heater valve that diverts hot water into the heater core. The vacuum line runs from the back of the control panel, through the firewall, and into the heater valve in the engine compartment. That would be the first thing I would check.

If the air is heating some, then there might be an issue with the diverter which switches between cold and hot. This diverter is controlled by the lever on the control panel.

There might be a few leaves or a bunch of leaves in the heater box.

You can do a search on the site for more information concerning these issues.

Upon closer look under the hood, I saw that the heater hoses were cut and left that way so no hot water coming in at all. I will get pics tomorrow.

From what I understand one of those hoses goes to the water pump and the other to the radiator correct? I saw the pump has a plug and the radiator was also plugged where the hose goes.

As for leaves, etc I did have some debris on my floor after turning on the fan so I know there's something in there. I can also hear things rolling around somewhere in that box with the fan on. I need to get under there to find that inspection window. Is that were I would be able to clean it out?

[Richard]

Originally Posted by r8rs4lf

Upon closer look under the hood, I saw that the heater hoses were cut and left that way so no hot water coming in at all. I will get pics tomorrow.

From what I understand one of those hoses goes to the water pump and the other to the radiator correct? I saw the pump has a plug and the radiator was also plugged where the hose goes.

As for leaves, etc I did have some debris on my floor after turning on the fan so I know there's something in there. I can also hear things rolling around somewhere in that box with the fan on. I need to get under there to find that inspection window. Is that were I would be able to clean it out?

I would guess the heater core is leaking so it was disconnected. A bit of work to replace on an A/C equipped system. There is a box inside that has a flap inside that is common to fail after the many years as well. Should check when core is replaced. If in your position I would assume the heater core is bad.

Edit- Aluminum heater core https://classicparts.com/chevy-gmc/t...-core-with-a-c
Copper/brass core like original https://classicparts.com/chevy-gmc/t...ore-with-a-c-1
Both will probably be a bit loose in the mounts because they are thinner than the originals. Some foam tape will fill the gap.
The diverter box I mentioned to check https://classicparts.com/1967-72-air...r-diverter-box

[r8rs4lf]

Originally Posted by Richard

I would guess the heater core is leaking so it was disconnected. A bit of work to replace on an A/C equipped system. There is a box inside that has a flap inside that is common to fail after the many years as well. Should check when core is replaced. If in your position I would assume the heater core is bad.

Edit- Aluminum heater core https://classicparts.com/chevy-gmc/t...-core-with-a-c
Copper/brass core like original https://classicparts.com/chevy-gmc/t...ore-with-a-c-1
Both will probably be a bit loose in the mounts because they are thinner than the originals. Some foam tape will fill the gap.
The diverter box I mentioned to check https://classicparts.com/1967-72-air...r-diverter-box

Can I run water through the heater core to see if it's leaking?

I'm going to contact the previous owner in the AM to see if he knows anything about it.

[PbFut]

Strongly suggest you not run the blower or fill the core until you clean out the vents and clear all the debris. You really don't want rat and mice urine dust pooop and dirt pushed past the core and ac evaporator into the rest of the ducts. Bad for your health and it stinks. The truck is 50 years old. There is going to be more stuff in the intakes that you can't imagine. Testing the core with stuff like my box had in it will just make a bigger mess. The hoses were disconnected for a reason. Leak most likely.

[r8rs4lf]

First off, can someone tell me why my pics are sideways because that's not how they are on my phone.

Anyways, the first and second pic shows the hoses cut off.

The third pic, is that one of the nuts I need to remove to get the heater core assembly out?

[425HP409]

You will have to remove the nuts that are on the engine side to remove the heater assy. An essential item to have is the assembly manual. This will tell all you need to know about how your truck is put together. A good idea to also remove the blower motor under the right fender.

[Rust_never_sleeps]

Originally Posted by r8rs4lf

First off, can someone tell me why my pics are sideways because that's not how they are on my phone

You can try switching hands to rotate your phone 180, but it's a common problem with the sw that runs this site

[dmjlambert]

I removed the passenger side inner fender and passenger side hood hinge to gain enough access to the various bolts nuts and screws.

[r8rs4lf]

Originally Posted by 425HP409

You will have to remove the nuts that are on the engine side to remove the heater assy. An essential item to have is the assembly manual. This will tell all you need to know about how your truck is put together. A good idea to also remove the blower motor under the right fender.

I have the assembly manual, but it's a PITA to navigate.

[Rick Bollinger]

Dmjlambert is correct. You need to remove or at least drop the inner fender as there is a bolt on the bottom that needs to come out. Your system will need to be completly cleaned out to work properly but when it is it does work well. While your at it remove the two kick pannel vents and stick a vacuum hose down there to remove that junk as well. Old leaves turn to compost, and plug up the drain holes on the bottom and will rot it all out. If the truck was only driven in the warmer months the PO might have just bypassed the heater core to get the a/c as cold as possible. Hot water flowing through while the a/c is on is a common problem and that is the easiest "fix" for some.

[r8rs4lf]

Originally Posted by Rick Bollinger

Dmjlambert is correct. You need to remove or at least drop the inner fender as there is a bolt on the bottom that needs to come out. Your system will need to be completly cleaned out to work properly but when it is it does work well. While your at it remove the two kick pannel vents and stick a vacuum hose down there to remove that junk as well. Old leaves turn to compost, and plug up the drain holes on the bottom and will rot it all out. If the truck was only driven in the warmer months the PO might have just bypassed the heater core to get the a/c as cold as possible. Hot water flowing through while the a/c is on is a common problem and that is the easiest "fix" for some.

Makes sense.....

From what I understand there is a "blend" door that if not closed (or open) all the way during AC, can hinder the temp of the cold air. Is that correct?

[dmjlambert]

Yes, the blend door is on the under hood evaporator box and pictures and story of repairing the blend door in my thread I gave the link to in post #4 above. Max A/C is also achieved by all 3 A/C controls on the dash all the way to the left and that blocks outside air from the vent in the cowl on the passenger side, and recirculate vent open on the passenger side kick panel, if those vacuum actuators are working well. Many people just seal the vent shut that is on the cowl to keep outside air from ever coming in and figure if you want fresh air you can crack open a window.

[Rick Bollinger]

I have found that you can remove two of the three hood hinge bolts and pivit the hinge down far enough to remove the fan and shroud. It's easier than removing the hood and can be done by yourself. Completly removing and cleaning refurbishing the heat and a/c unit does take some time and effort. Don't expect to get it done in a day or even two it is pretty intense. This is mine after my rebuild. Bead blast and clearcoated. I did reuse the evap coil and heater coil. New gasket set and kick panel, blend door and outside air door in cowl were replaced.