Getting up the nerve to tackle A/C, need to remove the old

[dmjlambert]

I have a 1969 Chevrolet CST/10 with original A/C and heat, 350 cubic inch engine and TH400 automatic transmission. The heater works, and the A/C has worked but doesn't hold refrigerant. The ducts have had modifications by the previous owner to accommodate broken levers in the controller and to accommodate re-routing flexible ducts because of a larger than normal radio. The result is the levers do not successfully switch between A/C outlets, heater outlet, and defrost. Instead, air blows out of everywhere for regardless of function (heat, A/C, defrost).

I have tried investigating the diverters with most components in the truck, by removing the S-box and looking at the cold/hot flap and heat/defrost flap and their connection to the controller, and although the controller moves the flaps some and the flaps do not appear to have anything broken, I was not really able to figure out why the setup does not divert the air properly in those cramped quarters, so I think it may be best to give it a closer look and clean up while removed.

My plan is to:
A. Remove all components the A/C and heat system,
B. Send the evaporator/blower unit out for restoration,
C. Replace all under hood components with a stage-3 kit from Original Air, this amounts to evaporator, condenser, compressor and compressor bracket, hoses, and the other components that refrigerant passes through, blower motor and fan. So, all under hood stuff will be new except evaporator box, which will be restored.
D. In the cab, remove the heater box and outlets, diverters, ducts.
E. Clean, inspect, repair or replace what is necessary, test, paint, and re-install.
I have already replaced the controller with a stock-type reproduction from Classic Industries, but I will remove it and use it to test the diverter on the bench, and I need access to the radio area anyway because I'll be putting a regular AM radio in there and new center vent, and while I'm at it, re-cover the dash pad.

Here are my questions, please:
1. What is the order of disassembly?
2. Can the inside-the cab components be removed first by just disconnecting the heater hoses and the rest of the unbolting is done from inside the cab?
3. Or do I need to first remove the inner passenger fender and hood and remove the evaporator box assembly in order to gain access to removing the cab's heater box?
4. I plan to remove the engine to do some work unrelated to the A/C in the engine compartment, but that is really a separate project. Would working on the A/C in the area of the evaporator box be significantly easier to do while the engine is out?
5. If I want to use the truck while the A/C and heater components are removed, how do I bypass the heater core?
6. The hoses going to the heater core are 5/8 and 3/4; do I force the 5/8 hose onto the too-big 3/4 fitting on the water pump, or do I fit the 3/4 hose over the too-small 5/8 fitting on the intake manifold and tighten it down with a hose clamp? Or do something else?
7. The heater core may be original and is not leaking and the heater works. The truck sat in a field from 1985 to 2014 when I received the truck, and the coolant was full, clean and green when I drained it after those years sitting. Is replacing the heater core recommended anyway? I'm just wondering if my old heater core is better than a new Chinese made one.
8. Any comments about my plan?

[Steeveedee]

As for bypassing the heater hoses, you can plug both ends at the engine with some purchased items, but I've jammed the 5/8" hose onto the 3/4" fitting when the heater core split, to make it home.

It'll be much more fun to do that work with the engine out, and in fact, if the right side fender and wheelhouse were off, it would be even more fun. You have to balance ease of the work- fender and wheelhouse off, or not.

If I were in there working on it on my own vehicle, I'd replace the heater core. I don't know that it has ever been replaced. HOWEVER, unless you have determined that the evaporator isn't leaking, and if the heater core isn't leaking, I personally would let sleeping demons lie.

My approach would be to install the other AC components and see if a good hard vacuum can be drawn and held to the spec. If that is the case, you don't need to go into the box after the evaporator or heater core, unless you just like needless pain and work. That might conflict with having the engine out, unless of course you install all the other AC stuff before taking the engine out, which really isn't all that much more work, on and off, since you can pull the compressor and hoses to the side when the engine comes out.

[Katrina/10]

Usually the hinge is bad on the cable operated flapper causing the failure in diverting air from floor to dash.

[Davidf]

Originally Posted by Katrina/10

Usually the hinge is bad on the cable operated flapper causing the failure in diverting air from floor to dash.

On mine, I found that the heat/defrost flapper just needed a good cleaning and grease. Before, the lever would move the flapper and manual assistance was needed. Now that the old grease was cleaned and new applied (where position tang slides against inside of box) it works perfectly.

[randy500]

Your going with a shotgun approach under the hood which will probably fix your leak and get you a bunch of cheap looking and I’ll fitting parts.
I would suggest finding your leak or replacing components that are likely leaking.
Your leak is probably the high pressure rubber line and the large o-rings that seal each one of the compressor. Often those only leak under high pressure and can’t be found by pulling a vacuum.
I pressurize the system using nitrogen because it’s very dry and you can pressurize it to extreme operating system pressures, 300psi or so and look for leaks with soap and water solution. You could use dry compressed air.
For the least cost most benefit just buy a new compressor four seasons part number 58096, $267 on amazon, it’s metric threads but comes with the metric bolts to mount to stock brackets. Buy a new high pressure line, $40 or so from classic parts.com and o ring kit.
That seals up under hood likely leak points.

Remove the inner fender and hood hinge to remove the inner and outer boxes, you don’t gain anything by removing the engine. Prop up the hood at the rf using a stick, prop up the rear of the hood using a piece of long wood from the cowl to the core support.

The inner box has 2 inside sheet metal screws, 3/8 or 7/16 head, and 4 outside nuts, one by the heater hoses, one below that and 2 on the rh side which are easy to find.
There is usually mucho debris in front of the evaporator which is only accessible by removing the evaporator core.

Inside is easy to work on once you remove the glovebox liner and the radio.
Remove the 3/8 sheet metal screw above the floor vent and the screws holding it and the s duct to the diverter valve, then the inside box. Then remove the control panel.
The repro diverter valve is almost as good as the later gm ones sold about 2 years ago. I’m sure it’s got a broken hinge.
Buy a new cloth type hose set, the plastic replacement ones suck.
Fix all your stripped out holes with j nuts, on the metal or plastic parts, stripped holes in the fiberglass, use resin and toothpicks, then re drill the holes.

[dmjlambert]

Originally Posted by randy500

The inner box has 2 inside sheet metal screws, 3/8 or 7/16 head, and 4 outside nuts, one by the heater hoses, one below that and 2 on the rh side which are easy to find.

OK I'm now trying to remove the heater core box from inside the cab. Am I understanding correctly I must remove the inner fender first to get to and remove a nut so I can remove the heater core box from the cab?

[dmjlambert]

Originally Posted by Bigdav160

I would yes, it's easier with the inner fender out of the way. (never tried to access the nuts with it on)

OK, so order of disassembly is under the hood first, then inside the cab.

Originally Posted by randy500

The repro diverter valve is almost as good as the later gm ones sold about 2 years ago. I’m sure it’s got a broken hinge.

OK, what does this mean? I don't know what GM was selling 2 years ago and I do not know what is worth buying and what is not.

I have found 2 diverters in 2 different boxes. One is to choose from dash outlets to heater outlets, the flapper does not work well.
The other diverter is to choose from heater outlets or defroster outlets, and on that one the metal flapper is rusted off the hinge pin so it does not work at all.

What are my options for those 2 boxes?

Originally Posted by randy500

Fix all your stripped out holes with j nuts, on the metal or plastic parts, stripped holes in the fiberglass, use resin and toothpicks, then re drill the holes.

What sort of resin are you talking about? Do you mean plain old epoxy that I squeeze out of tubes and mix, or something else?

[Bigdav160]

I would yes, it's easier with the inner fender out of the way. (never tried to access the nuts with it on)

[randy500]

Under the hood should be first.

Im saying the plastic divertrr valve repro part is a good part

The metal diverter is the same as a non ac truck if you have one of those laying around, not reproduced that i know if and usually are in good condition used.

[dmjlambert]

Originally Posted by randy500

The metal diverter is the same as a non ac truck if you have one of those laying around, not reproduced that i know if and usually are in good condition used.

This is great info, thanks. Used ones I see listed for sale are listed as non-AC truck. So knowing they are the same on AC and non-AC trucks is useful.

Here is the condition of mine. The pin that goes through the box is completely detached from the flapper due to rust. Is this one too far gone for me to repair and I should look for a used one in better shape?

[randy500]

2 part epoxy is fine.

[cebra]

I would get a used one, they are everywhere so I wouldn't expect to pay over $30 shipped for that part. I just threw mine away a couple months ago as it wasn't worth the trip to the post office to ship it to me (I switched to VA).

[F.A.A.benny]

Is Original Air going to restore your evaporator housing? Just curious as to how much they are charging these days

[dmjlambert]

I don't remember exactly, because it has been a year since I talked to them. I seem to recall it was about the same as you charge. I can't find my notes. They are going to install their evaporator into it. Since I am going this direction with the A/C, I am on my own to figure out the inside the cab components. Their kit and services include under the hood components, and don't include everything like Vintage Air and other you-no-longer-have-a-glovebox vendors. So, I'm concentrating on the in-cab stuff right now, and if I can get that to 100% then I will proceed to under the hood.

[dmjlambert]

Progress. Today I spent removing the passenger side inner fender. I sure like this forum, lots of great information here. Thank you all for posting lots of great info and pictures.

I found out what the deal is about the square nuts that spin freely on the inside of the fender while I was trying to loosen the bolts from the wheel well. I had to grip the square nuts by reaching into some pretty remote places, and when done removing the bolt, I brought away with my crescent wrench just a rusty square nut. I couldn't figure out what should have been holding those in place and what would normally keep them from spinning until I looked at threads here like this one. So, they are called J-nuts. After 50 years they are just plain square nuts partnered with a teaspoon of red rusty particles.

I was lucky that all of them were reachable except one which is a few inches to the rear of the center of the wheel opening. That is the only one I was not going to be able to reach from the inside, and it so happens that is the only J-nut I had that was in good shape and working. Lucky me! Ok, now done with body work, back to the A/C job.

[randy500]

The j nuts that remain good, i run a tap through them on a drill then oil them, makes assembly much easier. Barely start all bolts upon assembly till you have them all started otherwise the fender tweaks and one or a few might not line up. The 2 straight up bolts can be almost screwed all the way in since they hold the fender up and get the hole alignment happening.

[dmjlambert]

Today I removed the heater core box and cleaned it. Is the little door on the bottom a vent to blow warm air on the passenger's feet, or it it an inspection port for the fan resistors? Or both?

[dmjlambert]

I was out of order for a while due to having some surgery. Now I'm back in action. I removed the hood hinge and passenger side inner fender today, and unwrapped the rebuilt evaporator unit. I should have unwrapped the evaporator unit first. It looked impressive through the transparent bag they wrapped it in. I found some issues, so I'm going to put the truck back together for now and wait to see what Original Air has to say. I've asked in an email if they can help resolve.

There are some holes that I think should have been either worked with metal and solder or welding, or patched with something like POR15 and fiberglass.



The diverter door has a 7/8 inch gap when fully closed to the cold position, so the rubber seal on the door really doesn't do anything. This is the fully closed position, as far as the hinge will let it close.


The outside of it looks very nice.

[F.A.A.benny]

Id be ashamed of myself if I "restored" that ac unit. Original Air should have a talk with whoever worked on that housing and they should give you some type od refund. They didnt even remove the back metal plate because the original rivets are still there. And it looks like they left the plate bare metal.

[randy500]

Looks like they installed a new fan motor with a rusted out fan wheel too.

[F.A.A.benny]

Originally Posted by randy500

Looks like they installed a new fan motor with a rusted out fan wheel too.

You're right.

[dmjlambert]

Yeah, F.A.A.benny, I should have sent it to you. I'm sorry about that. I thought about it for a really long time. I can deal with the fan wheel and the holes. I can fix that sort of thing. I noticed the fan wheel as well, but not too concerned about it because I'm thinking of giving it the rsgt treatment.

I don't know what to do about the diverter door not closing all the way. Do you have any recommendations about that diverter door?

[F.A.A.benny]

If.i had to take a guess its most likely not closing all the way because the rubber seal has hardened and maybe curled, catching on the panel. Id that's the case you can try to cut some of the hardened seal to help close the door

[dmjlambert]

I now have some time to take this evaporator box apart like Original Air should have during the restore. Finishing the job. Rivets were easy to remove, and those same rivets are available new or I can use screws to put it back together.

Does anybody know what holds the pin in the door where I point the arrow in the picture? Is the pin just pressed in there and is it removable and re-installable? I was thinking if possible I would like to remove the door and put it on my workbench when fitting some new rubber on it. It would make the job easier and I would be able to get at both sides of the door.

[Undone]

It's just pressed in, once you get past the first hinge point above your arrow it will slide out. Use a punch on the pointed end.