halo everyone! It's been a busy summer, no time to hang out with my grease monkey chums on FTE!

Well here I am with a brand-new problem for y'all to gnaw on. The air conditioning in my 95 F350 was not working, as it turned out the compressor was shot. So I have a shiny new compressor, new seals and O-rings and gaskets galore, and it really blasts out the chilled air. I now have a rolling meat locker.

The problem is the compressor and the lines freeze up, which reduces the air flow, and no more chill. I turn it off for a couple of minutes, it thaws, then it's back to meatlocker. You can see the frost all over the compressor and the lines when you pop the hood.

It does this at all settings- low, medium, high fan speeds; Normal and Super Duper Mega Cool, or whatever the setting is. It takes longer on a very hot day, but it still happens. I suppose I can live with turning it on and off, but really now, that's just lame. Before I take it back to the shop, I request sage advice from the FTE Wise Guys.

Thanks!

 

I've got a '97 F350 that does the same. And I'm in Vegas where it gets really hot! It seems that on all but the hottest days, the evaporator freezes up. When this happens, I have to turn it off or switch to vent and run the fan motor on high until it thaws out. I have noticed that what makes the problem worse is when the humidity is high and I've got the fan on anything less than full blast! This makes sense though, since there is plenty of moisture in the air which condenses on the cold evaporator and then freezes, plus the air flow across the coils is not enough to "carry" the cold air away.

As for a solution to the problem, maybe a little less Freon in the system might warm things up a bit! It seems like these are very efficient A/C's, I've never owned a vehicle where the interior in actually comfortable when it's a 120 outside, but this one will do it!

Good luck!

 

Try wassing the condenser coils off. That usually is the cause of an A/C unit freezing.

Fire Rooster

 

Fire rooster, I have washed out the condensor on mine but still the same problem. The omly thing I can think could be causing it would be the blower motor is not putting out enough volume of air. Like if one of the windings were shot. I know from experience that high humidity and low air flow across the evaporator are the primary causes for freeze up. I guess I won't know for sure unless I replace the blower motor. When it's on high, the people in the back seat can't feel any air, and I can't really either, though what's coming out of the vents is ICE cold!

 

A couple things for you to look at...

1. Check that the evaporator isn't clogged. In my 2000 Ranger, I had to clean mine every 3 months or it would freeze.

2. Get a gauge and check your low side pressure. If you have problems with freezing, it may be low, not high. Remember, temperature of evapoation is directly proportional to pressure. As pressure goes down (like if the system is low), the temperature that the R-134 evaporates will go down, hemce freezing.

3. Did the shop replace the orifice tube when they replaced the compressor? Did they change the dessicant? Did they vacuum the system down? All of these can cause problems that maycause freezing.

I can't think of anything else for the moment. Hope some of this helps...

 

I talked to my shop persons, and this is what I found out:

- they cleaned the whole system thoroughly, including the evaporator
- don't know about dessicant, they'll check when I take it in
- the boss mechanic thinks the two likeliest suspects are either too-low pressure, or there is a switch that cycles the compressor on and off to prevent freezing. I'm taking it in next week, so we shall see.

They were mighty impressed by my list of questions, which I got from this thread!

 

Rancha9 has got some good advice. I also would suspect the blower too. Usually it is either a dirty coils or the blower.

Fire Rooster

 

Oops... Forgot about the blower... They can get leaves stuck in them too (Although they usually make a bunch of noise when they do). Do you have a tree with small-ish leaves in your yard?

 

Thanks for the advice on the evaporator being clogged. I never considered that. I actually do have two 40 year old (BIG) olive tress right over my driveway and the leaves fall and do get down in the cowling. Good Point!

Thanks again!

 

diesel-lady, Does the a/c compressor clutch stay engaged when the key is in the off position? If it does, the a/c relay may be stuck. If I remember corrrectly, the compressor clutch is engergized by the relay, which gets a signal from the low pressure/cycling switch.

 

Is this something I can easily check? I know nothing about A/C, except I must have it.

 

With the engine running and the a/c control in the off position, the plate on the front of the compressor shouldn't be spinning.

 

It was the cycle switch. No big deal. All fixed and working perfectly.

Oh, and I cured an annoying rattle- while I was doing an oil change I noticed that the shroud that covers the flywheel, right behind the oil pan, had lost two bolts, and the third one was hanging on by a thread. Got it all snugged down, and the truck is 10x quieter. Amazing what a racket a little thing like that can make.

 

I had a Dodge (I know, I was young, and stupid) Avenger that had a sheetmetal heat shield on the header that came loose. You're right, they make a LOT of noise!