Charging the AC in a 93 F-150

[WarPony]

I've got a '93 Ford truck that uses R-12. I put some gauges on and have 37 PSI on the low side and 205 PSI on the high side. It blows "cool" air but not cold.

Any AC mechanics out there familiar with Ford products?

Jeff

[SkipperSue]

What temp was it outside when you took the reading?
Do you have and dew forming on the low side where
it goes into the back of the compressor?

[SkipperSue]

Hey, I just noticed. I joined the forum exactly 2 years after you did.

[asianflava]

Beware the "Black Death" Ford compressors I guess use carbon vanes. When they wear out, they spread back junk all throughout the system. I was warned about it by my mechanic buddy and he was right, my Mazda/Ranger was suffering from it. What happens is, the black junk will start to clog up the expansion tube and not allow the system to cool. I don't know if your symptoms are the same but mine would be cold then when it cycled, it would not be cool anymore. I kept going like this till the compressor finally siezed up on me.

When I fixed it, I went ahead and converted it to R-134.

[Nitetimes]

Roll down the windows??? It's usually cheaper!!

[Steve Frederick]

The suction pressure of R-12 at 32-ish pounds indicates an evaporator temp around 32-degrees..about right! Unless it's really hot, 205# is a bit high for the discharge side!
Check the radiator/condenser (they're back-to-back) for debris. Maybe plugged up. It really sounds like a plugged cap-tube, as Rocky said, or a stuck expansion valve, if the system has one.
A shop with a vacuum pump and nitrogen may be able to clean it up.
Service on these systems is really for someone licensed to handle refrigerants. When I got my license, the fine was $10k for a release of freon into the air. Of course, you have to get caught!!

[WarPony]

GREAAAAAT!!!!!!!! This wasn't the news I was hoping for. When I took the readings, it was about 92 degrees in the shop. I can't remember if there was any condensation on the dryer or not. I did check the condenser core and could see through it AND the radiator so I don't think that is the problem but I will wash out the bugs and crap that's in there anyway.

Something I should also add to the mix: I just put in a new blower motor because the old one was growling. Come to find out, the blower motor resistor is bad, also, because only the high setting works.

Jeff

[Lesbest]

A/C work was a real popular job in the spring and I've done alot in 30 years. Something to look for-- you recharged it why? Was it low or empty?
If you did not remove the orifice tube and inspect it may only get cool, not cold. The orifice tube creates a restriction between the high and low side of the system, but if some of the desicant has moved out of the accumulator, been ground up in the compressor and caught by the orfice tube-you have another restriction which reduces the volume of refrigarent and reduces the evaporation process--reduces the "coldness" so to speak. The pressures sound good--maybe a little low on the high side. With 92 deg. 200 psig could be on the low side--250 to 300 is not out of the ordinary here. The bigger the heat load the higher the pressure, and humidity is a big factor on the heat load, and the sight of condensation. If your accumulator is not sweating then the volume of refrigerant moving into the evaporator is low, also you may be low on your charge.
If you used a charging station and put in 2 lbs, and thats what the specs are, you have a problem If you use 1 lb cans and now they only have 12 ozs in them it woukd take 2 cans and the better part of the third can to get 32 ozs.-or two lbs. So 2 cans would leave the system low and give you the symptoms you have.

Why is the system low? Those trucks had the spring lock connections and they were notorius for leaking, look for dirt around the connection,the mineral oil leaks with the R12 and collects dirt for an easy (relativly speaking) find. You can get girdle fittings for the connections to reinforce tham to help stop the leaks. They fit around the whole spring lock housing and are bolted together foe a more stable connection.
Let me know if this helps, and we'll see if we can't get you some cold air.
If you have the black death make sure you replace the accumulator as this is the start of this whole downward spiral of warmer and warmer air.

Good luck, Les

P.S. I reread your post--did you charge it or just check pressures?
Have you owned it since new and does it still have R12?
Did you buy it used and has it been converted to 134a?
Did some schmutz put in an unauthorized, but SNAP approver butane replacement?
If you just put on guages, and the R12 fittings are not altered, I would look for leaks and reasses the situation before spending a lot of money, just yet.
Let me know and we can work through this.

[Dayhiker]

If the system was low there is a posibility of air being in the system which will give false pressure readings. I see this more on 134 systems when people use the charge it at home kits. 134 is less forgiving than r12 but I agree the high side pressure could be a bit more the question I have is what is the temperature of the air coming out of the vents? Another thing to consider is a faulty heater control valve or blend door not sealing the easiest way to tell is check the temp at the vents then clamp the heater hoses closed and see if the temp goes down more than just a degree or 2 if you see a considerable drop in temp that means the hot water is circulating through and heating the air up before it comes through the vents.

Russell

[WarPony]

Whew.............. Les, you made me feel a whole bunch better!! We've had the truck for a year, so all the questions you asked about a retro fit of 134 or butane can't be answered. None of the fittings have the 134 quick couplers on them so I am thinking it's still R-12. The reason I was checking the system is because we are going on vacation in a couple of weeks and was told, "All I need is the AC to work!"................. the pressure was on.

I went out tonight and goofed with it and noticed the compressor making some noise (clicking) while it was running........... I know that isn't good. The compressor wouldn't cycle at all until I happened to wash the bugs out of the condenser and then it started to cycle on and off......... short cylcing, too. Once I got into the cab and revved the engine to around 2,500 RPM's, the compressor started to cycle but would only stay off for about 3 seconds before the clutch engaged.

[Dayhiker]

If the compressor is short cycling then the system is low on charge most likely.

Russell

[asianflava]

The famous, "All you gotta do is..." Gets ya all the time. Glad you got it worked out.

[WarPony]

The famous, "All you gotta do is..." Gets ya all the time. Glad you got it worked out.

Whoa, ho, ho......... I haven't worked ANYTHING out yet, Rockster!!

Famous last words? "It worked 'til I fixed it!!"

Kidding aside, I might try sticking in some more R-12 and see what happens.

Jeff

[Lesbest]

Without the presence of odd fittings it is a good chance that it is still R12. Short cycling is caused by the pressure switch on top of the accumulator opening and closing too quickly--usually because of a low charge. The switch is on at 40 to 48 psig and off at 30 to 35 psig. R12 has a pressure-Temp relationship that is pretty close to the same. 70 degrees=70 psi. at higher pressures the temp is a little lower. They shut the compressor off at 30-35 so the water that is collecting on the evaporator doesn't freeze, and still drains out of the housing.
If you don't have any huge globs of dirt on the connections look at the corners of the condenser for signs of dirt (leak).
I haven't bought any R12 in years so I don't know what it may be up to, (or down to), but to get thru your vacation drive with the least amount of chirping in the ear it may be easier to have some added. But like prunes how much is good and when is too good not good? The older systems had sight glasses and you could add till most of the bubbles were gone and you made cold air then. But they removed those from the systems and gave us an amount to fill to. If it is low ANY amount you add is a GUESS. When you put your pressure guage on the system and it shows pressure that is equal to the temp. of the day it tells you that R12 is in the system, a 1lb. can and a 30 lb. tank have the SAME pressure at the same temp. So it doesn't show the amount in the container. Check on a recover/evacuate/recharge price-- that will give you the best results, and the longer the evacuation the better--we would draw a vacuum for 1 hr. for our customers.
Adding a pound and checking temp can get you close to cold air, but is less reliable--could be under or overcharged. But is usually cheaper overall, now. This may get you out of hot water (air) now, aqnd after the vacation worry about a more permanent solution.
The best compliment to a good A/C job was to have the customer come back and say they needed a sweater in the car because it was too cold.

Hope this helps, Les

[WarPony]

Again, thanks Les. There is no sight glass in the system and I see no obvious oily joints at any of the connections.

Jeff