AC experts jump in here!

might be as easy as a bad pressure switch. The switch is mounted on top of the accumulator.
It could also be that all your freon leaked out. You will have to get the leak fixed and system recharged if that is that case.

I know this is what you don't want to hear, but he is right, there really isn't much to help with , could be many things!! If you have a electrical diagram, I would check for power and ground at the compressor when the car is running with the a/c on, if you have nothing, then it could be to low of pressure, or empty, or a electrical prob, sorry

I feel for you, I am fat as well... I bet it leaked out, check it out, it happened to me twice...

ID, im not an expert, but will try.
if i have it right, juice goes to the low pressure switch on the accumulator. it then goes to the WOT relay. then it goes to the clutch switch.

there are three wires in the LPS connector at the accumulator. IIRC, when the HVAC is set to a/c, they all show 12 volts. if this happens, you are ok on pressure.

next, i would check the wires to the WOT relay (under the intake tube). the insulation can vulcanize and come off. as you know, if you touch a couple of wires on that relay together, the relay kicks .

then at the clutch switch, IIRC one wire is ground, one is the 12 volt feed from the LPA and WOT relay.

that is just some basic info i know. Tom's great schematic will help illustrate what i cant articulate:
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

if you are low on pressure, you should not have 12 volts at all three wires on the LPS (low pressure = switch wont close).

of course, you could always just check low side pressure with a gauge, if you have one. i think R12 gauges are getting hard to buy these days.
that is all i got.

good luck, bud....

Mine went out on me a couple of years ago,too. Turned out to be that the compressor clutch was bad. It had a rubber damper that connected the actual clutch to the compressor (less shock load for the compressor,I guess). Anyway,it had disentigrated,and the only fix was a replacement clutch,it was somewhere around $125 or so from Advance. If this is the case,and it needs replacing,do yourself a favor and buy a *good* set of internal and external snap ring pliers. You'll thank yourself for it later on. The whole job took me about 1 1/2 hours to do,and I'd never done it before,so it's really not that hard to do. To see if this is the case,pop the hood,turn on the A/C with the engine running and see if the outer-most part of the clutch is turning with the pully. If it is,the clutch has done the same as mine did. You can actually see where the rubber damper tore itself apart if you look at it close enough. Good luck on it!

Idwitheld-1` said:

I put a paper clip across the pressure switch and the AC clutch engaged.

So, this means there is not enough cooling fluid?

Is this one of those cases where I should take it to a specialist and let them pressure test the system and recharge it? What do you think it will cost?

More money pumped in my car, but damit I love my car.

Click to expand...

when you bridged the a/c low pressure switch, you confirmed that you have continuity in all of the wiring and switches. so either: the LPS is kaputt, or you are indeed low on pressure.

i really dont know the goin rate on a/c stuff. i might see if a shop will test the low pressure side for you (if you dont have a gauge) - should be free. then go from there. if your pressure is ok, grab a new LPS switch. plug and play (no R12 loss when swapping switches). but if you are low, dont be tempted to run it with the paper clip - you might fry the compressor (not enough oil in the system).

if you are way short on R12, you could do a retrofit. R12 is goin for about 60 bucks a pound locally, so if you need more than a pound....retrofit kits are about 30 bucks.....
plus then you can top it up (since it is goin somewhere). just tossing out ideas.
thanks for the compliment, too. i try to get by.

good luck.

Idwitheld-1` said:

Hissin50, you said retrofit kits....what exactly does that mean? I have been told that R12 is still available beause it is recycled. But, is expensive (like you mentioned). Does this sound accurate?

I let it run with the paper clip for about 1 minute. No cold air and no condensation or coolness on the condenser canister (I think thats what it is called)? Seems to me its low on fluid.

When doing a R134 conversion, any thoughts on what is involved? Do I need an entire new system? Or do you think it would be cheaper to keep the R12 aliive for a few more years?

Sorry to bug ya with these questions.

Click to expand...

ID, never a problem; you know i enjoy trying to help people out - im no expert, but will tell ya what i think (i know). LOL.

it would really seem you are low on freon (R12). when you jumped the LPS, you should have gotten some cold output or atleast the lines to get cold. sounds like no.

so now, what to do. couple of options. very first thing i would do is to get the pressure checked. find a friend with a gauge or take it to a shop. i would not think they would charge you - it literally takes 30 seconds to check the pressure. there is high and low side pressure, but low is really what we would want to check out.

you are right - there is still R12 around. people with licenses can still buy it (for about 35 bucks a pound from parts stores). around here, it goes for about 60 bucks a pound installed. and you are right - some shops recover it. however, i dont like that. some folks have tried to top off R12 with R134, and the two are incompatible. so if a shop evacuates that guy's system and sells you his old stuff..............yuck.

if you are just a little low and there does not appear to be a noticable leak, you could pay a shop to stick some R12 in and some sealer (sealer i dont think works too well, but it might help). but here is where the pressure test helps out - if you are way way low on R12, i might just go get a retrofit kit and switch to R134 (since you will not be wasting any of your precious R12- you were about out of it anyhow). plus, if you have a leak, it is cheaper and easier to top off with R134 than R12.

the kits come from parts stores, wal mart, target, and so on. they are about 35 bucks from wal mart. the crux: you need to totally evacuate the old stuff from the system, along with any moisture - moisture kills a/c. of course, there are laws against venting any refrigerant into the atmosphere; an approved evacuation system must be used.

it might be most feasible for you to have a shop do this. they should pull around 30 inches of vac on the system for at least 15 mins. the longer, the better. some say that when retrofitting R134 into an R12 system, the o-rings should be changed and the dessicant (some redo everything). but many have simply vacuumed and refilled. if it does not work, you are only out about 35 bucks, should you have to open the system to change out some stuff. that is worth it to me (worth trying just the vac and retrofit).

to refill it, you will likely have to jump the LPS again (when the system is low or empty, the a/c, as you know, does not engage. this makes it hard to fill. LOL).
Jrichker has a write up on the retrofit in his home page. im too lazy to post the link (server and my dial up are slow). you will find it real quick.
that article gives good info. he used an old refrigerator pump to evacuate his system. that is over my head. that is why i thought having a shop do the evac might work well for you. you could call around. it should be cheap. and you could even ask the cost to do the whole evac and refill with R134. i have heard that it is not too bad vs just buying the kit yourself.

that is about all i can think of. i think this is fairly accurate. as always, i welcome folks to speak up if they disagree, so we all learn and i dont give bad info. i know there are some a/c certified folks in here.

ID, lemme know how this sounds and if it makes sense. take care.

a/c info

My a/c still works and blows cold, but not as cold as it should. So I believe I have a leak, probably at the o-rings I suspect. It is still an R12 system. I talked to an a/c tech at the local Ford dealer and he said if the r12 system still works, don't convert to r134. Everything I have ever heard about the conversion is that it just doesnt blow as cold. Our a/c systems were not made for it. Ford does sell a retrofit kit that includes a bigger condensor, air divertors and misc parts. Its a little more work than having your system evaced and putting in r134. To do it right you would need to flush out all the lines, drain and flush the compressor, condensor, and replace the evaporator and o-rings. I am not making this up. This is what I was told by many a/c guys. You can do the cheap conversion, but chances are you will be disappointed. I know because it was done on my truck before I bought it, and now I have no a/c in it. Just some info to think about.

defuzer, welcome to the boards. what you said is true. however, it is not cost effective for many to go that route. you are right, R134 intrinsically does not blow as cold. also there are pressure differences between the R12 and R134 (pressure required to operate properly). however, decent a/c is better than no a/c. and if one tries the retrofit and is not happy, they can certainly open up the system and replace all the things you list.

as i said above, one can try the retrofit, and if it does not work, that person is out a few bucks. but the risk is worth it, i think.

don't forget to change over the oil too. r-134a systems take PAG oil, R-12 systems take mineral oil. they say it is also a good idea to change over the accumulator while doing the conversion, because teh accumulator has dessicant bags in it that absorb moisture that in their age have probably been maxed out. the main reason you convert to r-134a is because not only is it better for the environment but it is a ton cheaper in the future, but then again if you have no leaks for 10 years it really doesn't matter. and technically R-12 is awsome if it weren't for being bad for the ozone, it cools 6 degrees cooler then r-134a and doesn't seep through hoses as easy, that's why systems that were set up for r-12 don't cool as well as when they are retrofitted because condensors and evaporators are different sizes and cool differently. I just saw a full R-12 machine for 100 bucks at a swap meet damn good price though. but anywho you did a great job HISSIN50 describing all of that, probably better than some A/C techs.

BG, thanks for the kind words, though i dont think i described it too well. i have had a/c issues, and i need a/c since i live a quarter mile from the sun; it is gonna be 100* tomorrow. so i try to have a working knowledge of how some of it works.

BG, you made a several excellent points that i neglected/forgot to hit. amongst them, the R134 molecules are a ton smaller than R12, which exacerbates leaks, as you said.
i have never known much about the desicant bag stuff, other than that it is recommended to replace it. but i tend not to. i am just happy to get the system to work, and im so poor, i try not to spend more money on it (the more money you spend up front, the more likely there is gonna be a big problem - that is a well known rule. LOL). i have not priced accumulators, but assume they are pricey.....but a good idea if one can do it. i think having the system open is what really really kills the dessicant bags. were that the case, it would almost be a necessity. but then again, some people will close a system and have it all work fine. kind of a luck thing.

ID, im glad you and i are sorta on the same line of thinking. my take is that there are so many components that can fail on the a/c, i retrofit them and then fix stuff from there. as BG pointed out, you can have a small leak, but it becomes a faster leak once the R134 is in there. but then again, at 5 bucks a can for R134.......i always worry about keeping the right ratio of oil to refrigrerant when topping up though. too much or too little oil is bad.

also, ID, i agree with having a shop do it. if you have been wrenching a lot, i know it gets old. been there, done that. LOL.
and a/c is one of those things where sometimes it is better to have a shop look it over (if you know the shop - a lot of them are rip off joints. no offense to anyone here who is an a/c pro, but i think you would agree, some shops will tell a person they need all new everything, when they dont). choose carefully, and let the shop do it. i have read some real horror stories in some other forums. call and get an estimate first (i like to ask prices for all the options. i.e. just evacuate. evacuate and retrofit. and so on. so you kinda know worst case). i know you know all that. i just like to aimlessly type.

but a/c is kinda like paint and body work, where unless one really kinda knows it, and wants to play, it can be better to have someone else do it. there are plenty of other things that will break that we can do ourselves. like there are some die hard wrenchers i know, who all have one thing they dont do. for some it is slushboxes. others, it is paint. and so on. having the right tools and stuff is half of it with a/c. and like i said, i have heard some quite reasonable quotes for a/c retrofitting (with evacuation).

good luck, ID and let us know how it all goes and what you think. im always curious about experiences and my mom's family still lives in Hillsboro, so i always have an ear out for good shops for them.
good luck.

This should help you if you decide to convert to R134a.

How to charge an A/C system.

Note: This method will work for any automobile A/C system regardless of refrigerant type. The pressures I list here will only be correct for HC’s.


This ENTIRE process makes a few IMPORTANT assumptions!!
1. The ambient air is OVER about 84 degs.
2. You have a set of A/C gauges
3. You do not take shortcuts.
4. You are able to read and comprehend english.

This process will work down to about 80 degs ambient air, but will be MUCH MUCH easier to over charge below 85 degs ambient air!! Relative high side pressures will be lower at 80 degs ambient and pressure drop after wetting the condenser will be less dramatic.

Pull a hard vacuum for a minimum of 15 minutes, 60 minutes is perfect. Static charge the system to about 65 psi while the engine is NOT running.

If you have a low pressure cut out switch on your system you will need to adjust it down to 18-19 psi sometime during this process. Personally, I find it easiest to do this about midway (now) through the charging process. Remove the connector from the switch and turn the adjustor screw about 1 full turn counterclockwise from its factory position. (counterclockwise is less psi, clockwise is more psi, 99% of the time) Start the engine and turn on the A/C, recirc, max fan, and engine at idle. Max fan is important, since it will help keep the evaporator from freezing as you charge. Charge the system slowly (if you have to!) until the compressor stays on fairly continuously at IDLE. The adjustment I illustrated above should give you a cut out psi of 12-18 psi. Watch your low side gauge and SLOWLY increase engine rpm. The low side pressure will drop slowly but substantially because you are still undercharged. Watch it drop from 20+ psi down through the teens and carefully note where the compressor cuts out. Return the engine to idle and pull the connector to the cut out switch and adjust it accordingly. Try this several times until, as the engine is slowly revved the compressor cuts out at about 18-19 psi on the low side.

The Charge:
Bring the engine rpms up to a continuous 1200-1800 rpm. Begin to add refrigerant (if you have to) SLOWLY until you notice that the air at the vents is noticeably cooler than the ambient air, say at about 65-75 degs or so.
At this point grab your garden hose and hose down the condenser; soak it once only. Your pressures will drop dramatically. The high side should drop below 150 and the low side should drop low enough to cycle the compressor, or if the switch is temporarily “jumped” the low side should be well below 20 psi. I prefer at this stage to jump the connector to the pressure switch to keep the compressor running continuously. It makes the process go much faster, but you risk freezing the evaporator. Now, watch the system pressures rise as the water evaporates and the heat in the system and stabilizes and equalizes. This can take a long time if you have a mechanical radiator fan. The point where the pressures remain relatively constant is called equalization.

Here is the key:
(After wetting the condenser) As you are watching the high side pressure rise from 160psi through (potentially) about 205psi the LOW side should REMAIN from 21-24 psi. If the high side never sees 145+psi you are still low on charge as long as the ambient is 85 degs or above. If as the high side needle swings through 160psi the low side is still below 20psi, you will add more refrigerant AFTER wetting the condenser again and dropping the pressures. Keep doing this until the low side remains at 21-24 psi while the high side swings through 160psi and finally settles at equalization (no more rise) Keep the engine rpms constant and wait for equalization (or close) each time before wetting and charging. If you are going carefully and slowly you could see a high side over 225 at equalization BEFORE you reach a full charge. The high side will DROP as you come closer to a full charge. Be aware that if you over-charge, the high side will climb again and never come down.

Note: If the ambient air is above 95 degs, stop watching the low side after the high side climbs past 205 or so. Especially if you have weak fans.

Note: Take your time and wait for equalization and water evaporation off the condenser before adding refrigerant. An overcharge can occur with no more than an extra 1.5 ounces of refrigerant!!

You can double-check your work at any time (and I suggest doing so) by waiting for full equalization and stabilization of pressures. Then, carefully MIST water into the condenser SLOWLY SLOWLY dropping the system pressures and watching for the same readings on the gauges as listed above.

When finished you should have a sweaty return line all the way back to the compressor. When the return line begins to feel chilled over the first portion of its length, you are approaching full charge. Do not forget to reconnect the low pressure cut out switch!

Do not consider your vent temps accurate until the vehicle has been driven for about 10 minutes at moderate highway speeds!!!! Idle low side pressure should not exceed 40 psi (34-38 actual) if everything is working well; good fans etc….

The idea here is that the compressor should NOT cycle when ambient air temps are above 81-84 degs.

Interesting note for tech heads: If you are charging SLOWLY. You will find at first that the high side will be at a higher pressure, after equalization, on a low charge than at a correct charge! Remember, raised heat = expansion and/or pressure.
Why: (basically)
Within a certain range, the pressure in the condenser (high side) is MUCH more affected/determined by the temperature of the refrigerant than its volume.
ALL THINGS BEING EQUAL, the condenser has the ability to lower the temperature of the refrigerant passing through it “X” amount and no more. The compressor, in compressing the refrigerant, heats or raises the temperature of the refrigerant “Y” amount. Lets say the temperature of the refrigerant entering the compressor via the return line is “Z”. So the final temperature “T” of the refrigerant that gets to the orifice/exp valve is: Z+Y-X=T
If we could lower the value of “T” the entire system would work more thermally efficiently and at lower pressures on the high side. So, ALL THINGS BEING EQUAL, you could 1. get a larger condenser and raise your “X” value or 2. lower the value “Z”.
A full charge on an A/C system will not only have enough refrigerant in it to keep the evaporator “chilled”, but JUST ENOUGH that the line leaving the evaporator and returning to the compressor will also have substantially cooled refrigerant in it THUS LOWERING YOUR “Z” value!! Hello!!
Note: Over charging will allow actual condensed refrigerant (liquid) to make it all the way back to the compressor. As we all know, you cannot compress a liquid…boom/screech.

jeez, you sure like to type "89saleen", but that is some very good advice. If I didn't have the tools I don't think I would attemp a retro fit just because of how long it takes. and if you don't have a leak detector then you really can't be sure that things aren't leaking and sealed well. I love to use a high tech computer to charge do a vaccum and recover, because like most of America I am lazy

and "HISSIN" the Accumulator thing isn't needed, it's just somthing that if the customer has some extra money and doesn't mind doin it then you might as well , it's just some added insurance, but if it was my car I don't think I would

bgjohnson - You don't necessarly need a leak detector to know whether your system is leak free. After you pull vacuum on the system let it sit for a few hours and see if it's still holding vaccum. If you can't maintain vacuum, then you know you have a leak in the system. Nine times out of ten, it's one of the O-rings at the springlock coulpers. Just replace all your O-rings and you should be good to go. Nice little trick is to coat all the new O-rings with Nylog before reinstalling. This will help keep them from drying out prematurely.

BG, thanks for the info on the accumulator.
89Saleen, i think i have seen that first post of yours before. great write up!