2002 Ex with a 7.3, 400k miles... The problem is that the A/C only cools when you're driving down the road... Had it set on 60 degrees and recirculate (max ac) and it did okay while driving down the road (especially considering it was 107 out). Problem is that when you're just sitting idling such as when in park or sitting at a stop light, it stops blowing cool and starts blowing warm, like if it were in "Vent" mode and possibly even a slight heat. Shop is saying compressor, although i'm not too sure. One shop cleaned the coil out and it helped some, and I know the radiator needs to have some fins straightened out too. Anybody experience anything like this? This truck has been tuned with a superchip as well if that makes any difference.

 

Anyone checked the refrigerant charge?

Hooked up gauges to the high and low pressure side and seen the values?

 

Yes, i dont know what the pressures were, they said it was low on charge and added some refrigerant to the system.

 

I recently had a new compressor put on and am experiencing the same thing. Would a grounding kit or a larger alternator help?

 

Without knowing the low and high side pressures, everything else is a guess.

 

I had the exact same thing happen on my beater. Driving in town it would not cool down anymore.. Driving freeway it would cool down after a while.
I hooked up one of the cheap gauges. It wasn't even empty, but a tiny bit low. I added only half a can of refrigerant and it works like new again.
I'd check that first. Do NOT overfill. do NOT use any leak sealer. Only r134a refrigerant and if you need more than a can you probably have a big leak and the fix will be short term.

The cheap kits only check the low side pressure. Doesn't say much about the condition of your AC system.

 

To me, it feels like an issue with electrical power. When you're driving the alternator usually puts out a little more power and you can feel that through the A/C system. When idle it feels like you have a loss of power and the A/C can't keep up. Is there any validity to what I'm saying.

 

IAC valve ?

the ac is run mechanical. I think the engine mangement increases the rpm slightly to compensate.

 

The vast majority of "poor cooling at idle" problems are caused by poor condenser airflow. You've verified the charge level and cleaned the condenser somewhat.
With the AC running on Max, 1000 rpm, high blower, have someone hose down the condenser with the garden hose for a couple of minutes.

Does the cooling improve? If so, replace the fan clutch, it is weak. The very first sign of a failing fan clutch is poor AC cooling at idle/low speeds. Your engine won't notice until it gets really weak.
I've already done about 10 1998-2005 Ford fan clutches this season for this exact issue.

If it cools well at 107 degrees going down the highway, there is NOTHING wrong with your compressor. Find another shop, quickly! If you connect a manifold gauge set to the system, I'll bet $5 that you will see the High Side pressure climb steadily upward when sitting still (until about 450psi when the high pressure switch turns off the compressor).

 

After an hour and a half of running 75mph down the highway at 107 outside, it wasnt frigid inside the cab, which I wouldnt expect, especially considering the amount of real estate there is to cool inside these rigs. As soon as I hit the stop sign at the end of the off ramp, it was warm air blowing out the vents.

The radiator is dinged up quite a bit from 400k miles of highway and country road driving, so im sure that is a factor. My first step is going to be to take a fin comb to that and try and straighten them up.

I'll also check and see if there is any play in the fan clutch, which was also on my list of suspected issues. I'll also check all the coils up front to make sure everything can breathe easy. Other thing on my list was the clutch on the compressor itself. Its pulling in and releasing fine, just wondering if it isnt slipping some.

What other symptoms are there of an ailing fan clutch?
One other thing? Does the outside air sensor play any part in the AC? If i remember right, the display was showing 60 degrees outside when it obviously was not..

Interesting thing, at least 2 shops have said compressor needs replaced. I don't buy it either.

 

Can someone post instructions on how to check the fan clutch? Is this near the radiator area?

Like I said earlier, I am having similar issues, but I already had my compressor replaced. I know my compressor wasn't working at all. These are just additional issues.

 

The radiator can't get dinged up, the AC condenser sits squarely in front of it. What you see is bent fins on the condenser. That is a big part of your problem.
Try the fin comb if you like, but you WILL probably replace the condenser to solve the problem if it's as damaged as you indicate. BTDT. The comb is a great idea...in theory. If the condenser fins are flattened enough to block airflow that bad, you'll spend hours with it, with not much return.

I've never seen a condenser with damaged fins bad enough to kill AC operation at idle, just from high mile use. There was usually physical contact or a pressure washer involved.

A weak fan clutch can't be identified by play or resistance to movement.(Those things can tell you if its totally dead, but not if it's getting weak) The only way to positively check it is with a photo-tachometer under test conditions. The best test for a fan clutch is AC performance at idle, assuming that everything else in the AC system is up to par. The AC performance at idle will be affected long before anything else.

You will only know if the compressor is bad if you can read the High side pressure. The test is to block the airflow over the condenser (as you have by default already) and see what pressure it can achieve. If it's high, the compressor is fine.

You really need to get readings of both High and Low side pressures (1500 rpm, Max AC setting, High blower, doors open, for 5 minutes) in the system and post them here. Everything else is just shooting in the dark at this point.

 

I had these exact same symptoms on my work truck. Turned out it was a bad clutch for the radiator fan.

 

Okay... more info....

Spent about 3.5 hours today straightening fins and cleaning and degreasing the condensor. seemed to help a little bit but barely noticable. Hit the interstate (70mph), and right before I got off the interstate, i dropped it in neutral and let it idle all the way down. Still blew cool air, maybe just a tad warmer but still cool. Got to the end of the off ramp and at the stop sign, started to warm up. If sitting still and at a dead idle, hosing down condensor for a min didnt seem to help... Sitting still with no water, and holding rpms above 1000, it seemed to cool down, but not get super cold. Rear ac was not very cold either. Cant really feel the fan pulling air through to condensor, but I can sure feel it blowing out when the hoods open.

Found out its been to at least 3 places. 2 of which are owned by same people. I guess they all put charge in, pulled it out, put some in, pulled it out, couldnt really figure it out and just said bad compressor. The first couple shops didnt even see the condensor was dirty, the last one did. Have no idea on the pressures.

At this point, next step is to throw a set of feeler gauges on the compressor clutch to check the air gap. If thats good, it'll probably go back to a shop. Im starting to wonder if all their pulling in and taking out, if they didnt screw up the charge, and the real issue was a dirty condensor to begin with.

 

Have to echo my first post and "HD RULES" and lsrx101.

You MUST determine the high and low pressures. Doing ANYTHING else is just stabbing in the dark.