A/C & Heater fix

Now that my car is driveable, I’m looking into fixing the whole A/C system and getting it back to working order. I’ve never messed with AC, and I was unsure of how to proceed, hopefully I can get a better plan once I lay out all the issues I’ve got.

First off, I’ve got to take apart the dash, get in the heater core box, and replace the heater core and find out why my blower motor doesn’t work. I’ve got some vacuum lines that aren’t where they say they should be, and some wiring to the compressor that the PO put in, so I’ll have to look at their handiwork and see what they did. My heater core seems to leak a bit, and the box had the drain hose plug kicked off of it before I got it, so I’ll have to fix that and stop it from draining right into the passenger footwell.

While I’m in there I’ll look at the evaporator, and see how it is, not sure how to test if it’s still good or not. I’m hoping that the heater core isn’t cracked, I can braze it if need be though. If the evaporator is not airtight, is there a point in trying to fix it? I would think with the pressure that goes through it that it wouldn’t be worth trying to fix it over and over if it doesn’t go right. Other than the evaporator, I’ve got some lines from the PO that don’t seem like the best, the fittings aren’t crimped on, they are in the hose with hose clamps very tight, so I may have to replace some lines. When I got the car it came with a Four Seasons 57034 Compressor, I was looking around and I assume thats an R12 model correct? I don’t see anything that looks like an R134a conversion, although I’m not sure what all goes into that.

That’s another thing I’ve got to choose, if I want to convert to r134a or stay with r12. I’m in southern california, so it gets pretty hot for at least half the year, and the stringent emissions here would probably cost quite a bit to get r12. I was looking through here for info and I saw someone mention that they use “FR-12” and had a link to it, would that be a suitable replacement for R12? It is advertised as a replacement for R12, however I was hoping someone else here might have some insight on that.

I’ve got a new condenser and drier from WCCC, so in terms of parts I believe I have everything, just not sure which parts to modify or how to check them. I took off the suction and discharge lines from the compressor, it had been sitting a while, and when I took them off, one side (I believe the suction) had what looked to be some oil dripping through. I tilted it around and no more came out, just the little that was sitting in the line. I spun the clutch to see if it would suck and blow and it does, the pulley spins fine and the clutch is a little hard to turn, not sure how hard it should be, but it takes a little effort. I’ve also got a spare York compressor somewhere, I’ve not messed with that since it was a leftover from some other car I never worked on.

So in parts, I’ve got a stock evaporator to check, a heater core to fix a leak on, a heater box to fix the drain plug, blower motor to inspect, some questionable AC lines, a Four Seasons compressor that I believe is still R12, and a new condenser and dryer.

Any advice or experience would be appreciated, my current plan is just to fix the fan and heater core, and then hopefully keep the system as an r12, or that FR-12, but I’ve got no real clue how to go about all that.

edit: just looked over that four seasons compressor, it says to fill with 6oz of PAG oil, which I thought was only used for r134a? The oil that came out was a yellow-greenish looking oil.

Once you have the evaporator out or can see it, look for an oily residue, anywhere on the evaporator fins or lines. If there is, it’s leaking and needs replaced. As far as retrofitting for R134, opinions vary but if it were mine, I would stick with R12 if possible. The system was designed to operate with R12, not 134. R12 is harder to find but still available but you’ll need an A/C license to buy it plus it’s expensive, so leaks are unacceptable! While 134 behaves similar to 12, it does have some compatibility and performance issues with older vehicles and can leak where 12 didn’t. As I stated in a different thread, R134 is being phased out and replaced but yf1234 and there is no retrofit for the newest refrigerant in older systems.

Ok, I’ll look for that on the evaporator, hopefully I’ll be getting that out this week and can check on it. I definitely would prefer to stay with r12, less modifying the system and if they are swapping to that yf1234 than I’d rather not swap to r134a if it’s on the way out.

I’ll see if I can post a picture of the hoses that were on the system when I got the car. PO said they were find and held a charge, the system just needed to be charged, but I am unsure.

Since I saw that oil on the suction port of the compressor, do I need to disassemble it to see if it’s leaking or is that common? It is a green color, so it’s either that PAG oil from what I’ve read, or perhaps ester oil as I read that Four Seasons fills their units with ester oil.

There are some oils out there that are compatible with both 12 and 134. If you see green, that’s dye that has been added and indicates a leak. Now since its by the port its possible it’'s just some blow back when the hoses were connected or disconnected. They have leak detectors for 12 and 134, had them both, didn’t trust either, as you could burp and into them and they would go off. I’m old school and use good ole soapy water and look for bubbles, easy to see and confirm if there’s a leak. I would shy away from the “blended” refrigerant with any type additives, that seldom ends well.

Soapy water works for checking my welding setup so I’m sure I can get away with that too, thanks.

Is there anything I should replace on the compressor? Any disassembly I should do to check on internals? I also was wondering about which fittings use O-rings, none of the lines I have had any in them when I disconnected them.

And lastly for now, how do you fill the compressor with new oil? I see a bolt on top that just goes into the casing, not holding anything together, would that be the fill plug?

That is the fill plug you will need a shop manual to see and get the dimensions needed to fab your dip stick as the commpressor doesnt have one.

Minimum I would do on an unknown system that is discharged:

  1. Replace the receiver / dryer.
  2. Replace the expansion valve.
  3. Flush the evaporator, hoses and condenser with 90 % isopropyl alcohol.
  4. Replace the compressor with an overhauled unit or have the original overhauled.
  5. Replace the heater core with a new one.
  6. Check the oil in the compressor as per the shop manual.
  7. Inspect and test the A/C clutch per the shop manual
  8. Inspect and test the icing switch per the shop manual. Replace if it does not open when at the specified temperature.
  9. Reassemble and vacuum test everything. Fix any leaks that are found.
  10. Charge the system as per the shop manual.

I’ll see what I can do about that dipstick, thanks.

I’ve got a new dryer, I’ll look into getting a new expansion valve, I’ll probably end up replacing the hoses and I’ve already replaced the condenser, I’ll flush the evaporator when I take it out with the heater core.

Is there anyway to check if my compressor is fine opposed to replacing it or paying to rebuild it? I am pretty sure the Four Seasons compressor I have is fairly new, the PO did the wiring for it to work and he only had it for a short time. If there’s no good way way test it I’ll look for a replacement.

All that stuff afterwards requires a shop manual which I unfortunately don’t have, and WCCC says they don’t have them/have been discontinued, but I see they have a USB version so I’ll look into that. Thanks.

I didn’t see anything about O-rings in there, would new hoses come with those or do I need some specific ones from WCCC or another shop?

I am not seeing anything in your post or your signature that tells us what year shop manual that you need. In any case they are available used on eBay or Amazon or any discount book seller very cheap. The digital version is hard to use unless you print out all the pages that you think might be needed.

In 2019 I did everything Royce describes except the isopropanol flush - the system had been converted and I didn’t know any better anyway - plus I replaced all the foam seals in the flapper door empire with the WCCC kit. Mine were either dust or long-departed.

I found some dippy shop had broken the diverter/splitter for the footwell heat and just left it out upon reassembly. Likely didn’t tell the owner. Reproductions are available, though they don’t fit the greatest.

You will be in a small club and very satisfied when done.


I’ve got a 70 base model, I’ve been meaning to update the signature on here, sorry about that. I’ll check around for the hard copy, I’d prefer it to a digital but I may get both since I spend a lot of free time working at a computer anyway.

I’m sure I’ll have to get lots of seals and foam for the interior airways and the heater core box. I’m unsure if anything is broken in the system, the blower motor doesn’t blow so I am not sure if the splitter actually diverts air the correct way or anything, and the PO did some work to some vacuum lines so there could be other work there I have yet to discover.

I would go through everything until I had a high degree of confidence that a charge is all it needs to be functional.

I’m getting ready to tear into mine for a new heater core too. Think I’ve got all the needed heater box gaskets and the good core from WCCC. Is the reproduction Autolite heater hose from Marti Auto works good for long life? It’s already been sitting in my garage for 8 years. Been wondering what to do about my blower motor as well. Mine works, but is a bit noisy. Hoping I can get some oil into the bearings and it quiets down.

That’s what I plan to do with the fan and heater system, I’ll fix those up before I jump on the AC, so I can test if my fan blows correctly and all the positions/speeds work.

Is there a procedure for testing the blower motor? I’ve never messed with one so if someone’s got an idea of how to get through it I’d appreciate it. If I can order a TSM and get it in time maybe I’ll find something in there.

I need to look into hoses as well, both hoses going to my heater core are functional but not the most reliable looking setup, if the heater hose from Marti works well enough I may have to see if I can get one, or something similar.

I don’t have AC, and the heater hoses go through the firewall. So I need to be damned sure they are gonna last a good long time. The Gates hoses on there now are from 1990 so I’m on borrowed time.

The Shop Manual has lots of stuff and pics about removal and installation of HVAC equip, but there is nothing about the blower motor itself except that it should pull 7.4 to 9.6A with fan on high. There are also blower resistors that are used at lower fan speeds to drop voltage to the motor. If these are bad, they can also keep the blower from working at lower speeds.

Best of luck on the heater hoses, didn’t know they were that different on the non-AC cars.

I’ll keep those amperage in mind, I’ll probably have to do some research on how to go through the motor once I get it out. I’ve just about got the lower dash out now, should be out pretty soon.

Put battery voltage on it and measure amps.

Well I got the heater box/blower motor out today, had a few surprises from the PO.

A few of the vacuum lines were mixed up, still had original colored lines on, but they were in a few wrong spots. The Heat/Defroster vacuum motor wouldn’t hold vacuum, all the others held quite well. I was missing the Heater outlet to floor piece, so no floor vents, and the center piece had a missing screw on the driver side. Once I got the blower motor out, I saw that the positive wire just wasn’t hooked up, so I’ll have to test that. I got the heater box out and sadly, it was pretty mangled.

One of the brackets was ripped out, and had some plaster/epoxy over the spots where it broke the fiberglass. A few lips where the clips latch on were broken, and then I saw that the whole bottom half had a crack down the whole length of it. Looked like someone had tried to kick through it. It had also been plastered over, pretty poorly.

I took out the heater core, and found a small crack near one of the outlets, no other leaks, so that could probably be brazed or patched another way. My evaporator seemed fine as well, it had the same green oil in it leaking out, so I’ll be cleaning that out soon, and I gotta straighten out a few fins on it.

For testing the blower motor, I assume I can just put 12V at each of the 3 prongs one at a time and ground the motor to check the different speeds correct?

One other thing I noticed, when I took off the expansion valve, it was not the stock style, and it had the Green O-rings in it. From what I read, the green O-rings are specifically for r134-a, since it erodes regular O-rings, at least that’s what I’d read. So it seems at some point someone swapped it over, so I’m not sure if I’ll go with r12 or r134a. I’ll have to look more into the compressor and see if it’s meant for r12 or r134a, and then choose hoses from there. I’d prefer r12, but we’ll see how it goes.

It sounds like you are well aware of the polarity of the blower motor wiring but I’ll mention this anyway. My 70 also had numerous heater/AC issues but the one that I almost missed was that he blower was running backwards. Air flow was disappointing. The polarity to the motor was reversed. The blower will push some air when running backwards but not as much as it will running the correct rotation.

Just checked the speeds on my blower and they seem pretty good, all 3 prongs had different resistance to the output prong, and all 3 worked. I’m fairly certain I had the polarity correct, even at low speed I could feel a bit of air with the fan outside the casing. Just to be sure, I was looking at the motor with the squirrel cage fan facing me, it was rotating counterclockwise.

Now I’m just waiting on some parts from WCCC, so I’ll have time to clean a few things up. I do have a few questions that are still up in the air however.

The aftermarket expansion valve seems to have a lot more copper wire coming out than stock, is that due to it being an r134a expansion valve?
It had the green O-rings which are made of a different material than regular black O-rings, so I would think it was for r134a. Not sure how it would impede the performance of the AC however, if anyone could explain I would appreciate it.

Another thing is if anyone knows if having r12 in an r134a compressor would be bad. I know that r134a in an r12 compressor is bad due to the molecule size of r134a and it is less efficient and harder on the compressor, however would r12 in an r134a compressor have the opposite effect or would it still run worse? I read a few ideas saying that r12 is easier on the system due to lower pressure and larger molecule size, not sure how correct that sounds. The compressor I have is a Four Seasons 57034, on Summit they have almost every compressor labeled as r12 or r134a, except this one (just my luck). It seems that they mainly make them for r134a, so I would assume this one is as well.

I’ll post a lot of the pictures I took, damage and other things. Thanks.