help me diagnose my AC problem on my 66

factory air car, 66 belvedere, everything is there, connected, old but there...doesnt look to be in bad shape but anyways...i put in a new ac control unit, new heater/ac blower motor switch and go the fan working, so i charged the system up and wallah...air worked for about 2 hours...on way home, HOT AIR...so it leaked out three cans in about 2 hours time....but atleast it was working right?? well when i got the car it had a stain which is still there on passenger side carpet of antifreeze/coolant...whichever. i cant see any leaks under the hood, put dye in it and still nothing really....compressor looks dry, hoses...so im assuming its leaking under the dash and onto carpet still. i guess this is the condensor? heater core? valve? what do i need to look for and check before i go and pull this entire dash apart and heater box completely out...anyways to diagnose the problem? how hard is it to take out all that on a 66 belvedere? thanks for any help guys.....

Uncle Don said:

factory air car, 66 belvedere, everything is there, connected, old but there...doesnt look to be in bad shape but anyways...i put in a new ac control unit, new heater/ac blower motor switch and go the fan working, so i charged the system up and wallah...air worked for about 2 hours...on way home, HOT AIR...so it leaked out three cans in about 2 hours time....but atleast it was working right?? well when i got the car it had a stain which is still there on passenger side carpet of antifreeze/coolant...whichever. i cant see any leaks under the hood, put dye in it and still nothing really....compressor looks dry, hoses...so im assuming its leaking under the dash and onto carpet still. i guess this is the condensor? heater core? valve? what do i need to look for and check before i go and pull this entire dash apart and heater box completely out...anyways to diagnose the problem? how hard is it to take out all that on a 66 belvedere? thanks for any help guys.....

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Either buy a leak detector or take it to someone that has one, fill it again and start checking before you start tearing anything apart.

Sounds similar to what happened to my dad in our van ended up being the compressor? Air was barely coming out and it was leaking on the carpet. Of course your not having low pressure problem but you might be right about the hoses or something...

Just out of curiosity, what did you fill the system with?

Old A/C systems used R-12 refrigerant and before that something else... But EPA made the A/C industry switch to something else less harsh on the environment a few years back. So now R-12 is illegal ( at least in Ca. ) and very hard to find. Auto part stores sell R-134 for the home mechanics to use. I think even that refrigerant is going to be phased out pretty soon. But long story short... R-134 from Auto Zone will destroy the O'rings in your old system and cause it to leak somewhere... They sell O'ring kits made of Viton I think to retrofit your system... If that's the case that is. Just a little FYI if you weren't aware. Hope you are able to get it figured out soon. My ride doesn't even have A/C :sad:

A/C???? WTH is that??? :rolling: Wookie is right, r-134 will eat any of the old o-rings...good luck on finding your leak...

The coolant on the floor could be the heater core, or one of TWO water valves in the system (one in the heater box, the other on the firewall) My guess would be the one on the firewall. It protrudes inside the car and has a simple rubber seal on the back side (inside the car). Those go bad. There IS a "fix kit" available for that valve, but trust me, it's a major pain to replace. New valves are supposedly available

its 45 year old technology, all original stuff and i just dont know where to start...part of me says just take it all off, put whatever engine im going to put in there and later on down the road add the new classic auto air or vintage air or whatever...

but i hate to, just seems an extra cool(haha) factor to have the original ac working....im sure there werent very many 66 belvederes made with air..

your evaporator is probably rotten and leaking refrigerant.

“factory air car, 66 belvedere, everything is there, connected, old but there...doesnt look to be in bad shape but anyways...i put in a new ac control unit, new heater/ac blower motor switch and go the fan working, so i charged the system up and wallah...air worked for about 2 hours...on way home, HOT AIR...so it leaked out three cans in about 2 hours time....”
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Let me take this in parts.... Do you KNOW that the refrigerant leaked out? Have you put a gauge set on it to verify that it is not still pressurized? Did you check the oil level in the compressor when the system was empty? Did you put R-12, or one of the compatible butane based refrigerants in it when you charged it?...

The reason I ask this is because you later state that you put dye in it and still can't find the leak. This would indicate a failed expansion valve in a pressurized system, as a leak would be quite obvious with a UV (black) light, but only if the system had oil in it (which caries the dye).

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"well when i got the car it had a stain which is still there on passenger side carpet of antifreeze/coolant...whichever."
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If I understand this right (correct me if I'm understanding you wrong), the stain is not related to (caused by) your latest A/C charge and failure. If so, the stain is from the failure of the heater core, or possibly, but somewhat less likely, the heater valve. Heater core failures are nearly universal in A/C cars, as the A/C subjected them to nearly constant moisture and corrosion.

A/C systems that have been dormant for long periods of time will cause the seals to dry out/crack, and fail when pressed back into service. R-134 does not "eat seals", but requires oils that are not as compatible with the old rubber seals, so if the seals are in poor shape, they will fail when pressed back into service. Plus R-134 is molecularly smaller than R-12, and will leak past the seals and hoses (just like a rubber Helium balloon will leak out the Helium over a short period of time, but will still look inflated).

A perfect R-12 system that has been properly converted to R-134 will need an additional 1/2 to 1 can per year under the best of circumstances, unless all the seals and barrier hoses were changed. If the system was dormant for a couple of years, you can have total leak-out in just a couple hours in an otherwise perfect (looking) system, no matter what refrigerant is used, but dye should show the leaks if the oil level is correct.

It's quite probable that I have owned more of these cars than anyone on this board, but I guarantee that I have owned more with A/C than anyone else. In all those cars, I have never found a failed evaporator, as that’s where all the oil accumulates/settles, so I highly doubt that you have an evaporator problem.

Seals are the most common failure area and are easily changed once you find the leak. The expansion valve is also quite common in a system that has not been run for a few years, as a newly charged system can cause accumulations of trash to jam the valve.

I like to say --- You’re not American if your car doesn't have A/C --- toung in cheek of course, but where I live, A/C is absolutely essential.

AWESOME RESPONSE THANKS FOR TAKING THE TIME! now in saying that....here is what i did, (i know its not the best or correct way but it was easy and cheap). I got my switches hooked up, blower motor running, and compressor working....when i mean working the clutch was engaging with the switch and powering down the engine just a wee bit so i assume its working properly. now i DID NOT check the oil level in compressor...didnt even know i was suppose to. im new to the older ac units and how they work etc...so have to forgive me. so all i wanted to do is just see if this system still worked, i had the controls hooked up correctly etc...its very hard to get ahold of R12 around here anymore and when you do find it its pretty expensive. so i bought a R134 changeover kit from parts store and put the fittings on and put three cans in. the gauge read full(the cheap gauge that comes in these kits) so all was well...i tried it out one hot 100 degree day and wallah! it worked. cool air! i took the wife, kids out to dinner, to and from, stopped at a local cruise....all time i had air. when i got into car to come home...it was not as cool as before. So i assume it leaked out. i put another can of r134 dye in it, and i never seen it...maybe its leaking where i cant see it? not sure. eitherway my components seem to work but wont stay cold...so i have a friend that runs a automotive shop and happens to be a mopar nut...i thought about just taking it to him, let him put the proper gauges on it, run some test, etc...and go from there. that just gets really expensive.

while im thinking about it, how rare would you say a 66 belvedere with air is? i went to the nationals this past weekend in Columbus, OH and looked at several 66-67 belvederes, satallites, gtx's etc and none had air....when i try to find parts for it, no AC parts hardly....was just curious.

I would recommend that you take it to your mechanic friend, as you will otherwise have to invest in some A/C specific tools, and take the time to learn about A/C systems in general.

If you plan on doing more A/C work than just your own car, it's well worth the time/ money investment, but if you just want your A/C to work, an A/C tech is the quickest way particularly if your friend will give you a break on cost.

As far as rarity goes, I can't say, except that region has a lot to do with it. Out here in the southwest, most cars had air. I had a 66 Coronet that had air, as well as a 67 GTX, but all my cars have had air or else they got flipped to someone who didn't care.

Any A/C parts you need can come from most later model cars as there is very little difference over the years. Of course it depends on what you need, as things like the A/C heater cores have been discontinued for decades, but aftermarket ones are available though pricey.

FrankieG said:

your evaporator is probably rotten and leaking refrigerant.

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ok so a little update...didn't know if here is the right place or i might start a new thread also. its getting cold now, so i found out today that my heater does not work..meaning it blows air fine but its cold all the time...i checked the thingy on the inside of the firewall to make sure the cable from my cool to hot lever on the dash was working...so thats moved to the warm position, so no warm defrost or no warm floor heat....blah. so i guess this go's back to my earlier post in here that my heater core is bad? since there is refrigerant on the carpet..where one would leak. looking on fleabay the ones for my car look like back to back NON/AC heater cores...and almost $300 GOOD LORD...

so a few questions and hopefully you guys can help...
1. is there something else that would cause me not to have warm air coming out other than a heater core??? i hate to go thru all this trouble to replace it and it was something simple...just making sure.
2. anyone have any schematics of my ac box, heater core location, how that all comes out? how to change a heater core in a 66 belvedere ac car???
3. is there a good chance i put in a new heater core and it fixes my ac problems to??

thanks for any help you guys can give....

Are you sure the valve in the hose between block and firewall is opening to let hot water circulate thru the core? Did you vacuumn the system before you filled it. Did you let it sit on vacuumn and see if it lost vacuumn. This is a leak test. And did you hook up gauges to see the high and low pressures to determine the charge and compresser efficiency. I bought a vacuumn and gauges from harbor freight for less than a hundred dollars and theres a video on you tube that is very clear on how too.DD

i am not aware of such valve...i will have to check into that....is there an easy way other than having a vacuum test done....if its bad or not?

a/c heat problems

Don, You say there is refrigerant on the carpet? Do you mean coolant? Either way, you need to pull the air box and replace either the heater or evap. core. If you have it out, replace BOTH no matter what the cost. You will be glad you did in the long run. The valve that is referred to is in the heater hose on this model IIRC. It is to shut off hot water to the heater core while the a/c is on.

I'm a Refrigeration Mechanic in Canada and I would go to a trusted qualified person to find your problem then know your options.I have helped many friend who say they should have come to me first and not wasted time and money chasing the wrong problem.A couple tried things on there own or with someone who had seen it done before and damaged the system more than it was.It's money well spent .

im not sure what is on my carpet...i have green carpet and this is a lighter yellow color...so not sure if its anitfreeze, ac stuff or what...so if that valve is not working properly then my AC wouldnt work right either??...has anyone took out there heater/ac box out of a 66ish plymouth, dodge, etc...??? any pics? or is it just time consuming and get r done..?? im not afraid to do it, just don't want to break anything or take something off that doesnt need it. i will eventually take it to my friend on the ac stuff...but for right now i just want the heat to work so i can drive it some thru the winter here....i hate for it to set for months....

FYI it sucks taking out the unit!!!
Very big pain!

o.k. im starting a new post with pics...and questions...please see that, needing help. thanks guys......

Uncle Don