I've done some repairs. Truck is still R12. The fan is weak, but not horrible. It's been awhile since I measured, but I think I have 1-2volt drop in the circuit. I'll measure again here in a few. Cleaned out the heater/evap box. The previous owner had already cut an access panel. It wasn't that dirty. Had a shop replace the compressor, expansion valve, and one hose. Condenser and evaporator look original. Truck is low miles and clean. I've replaced the cycling switch twice now. First one was a junkyard piece. Second was NOS. First time out they both hit 40 then eventually maintain around 50. I've only had the second one for a couple days so still watching it's behavior, but it hasn't achieved 40 again. Maybe 42-45 then stabilize at 50. After driving for 30 minutes it will freeze and blow 60. Truck has always left a huge water mark on the ground after parked. Originally I thought I had a coolant leak. It's been this way since I owned it. Previous owner had jumpered across the cycling switch so it was worse.

First thing I probably need to get good voltage to the blower motor.. Maybe replace it. Secondly replace the condenser.

Anything I can check or replace. I'm thinking most shops are just too production for this job. I need some knowledge before taking it back in.

 

A few thoughts: low fan speed from a weak blower motor will definitely cause the evaporator to freeze...Did the shop that replaced the components also flush all the remaining lines and the condenser?...If not there may be a restriction before the refrigerant ever reaches the expansion valve......Ben

Edit: I did not add that link to my post, and have no idea why it's there...

 

My money is on two things. A/C cycle switch or the expansion valve. Mine did the same thing years ago, it would actually freeze over and blow show flakes, then froze completely and started blowing warm humid air. Shut if off for a bit to defrost and it was cold again until it froze over. I know you did the cycle switch twice, but do you hear it cycle the compressor? Perhaps there a wiring problem in the circuit?

 

I'm not sure if the shop did or not, I would hope so. I guess that's another thing to try. I should probably replace the condenser at that time.

 

Did the switch and the expansion valve both. No I haven't checked to see it actually cycles. I'll do that this morning. Before I put the switch in the previous owner had it jumpered. It would blow much cooler until it froze.

 

Well I just fired up the truck. AC on max windows closed. 75 degrees ambient. It got down to 36 and the compressor turned off. I was using my HF infrared probe pointing close to the cycle switch probe tube. Compressor would kick off at 39-40 and kick on at 46 so looks like the cycle switch is acting as it should. Didn't run long enough to freeze. I'm going to jumper fan motor direct to battery see if it picks up significantly.

Update:

Jumpered directly to fan. Fan picked up, but not as much as I liked. Enough to do Jim lane blower mod however. Also drove around long enough for the evap to freeze. Took about 45 minutes. Temps ranged from 40-48 until it froze then climbed to 60 with reduced airflow at vents. Picked up some groceries and on the drive home got back to low 40's with normal airflow at vents. Back to normal.

 

have you checked the Freon levels? Also you may have a bunch of debris, leaves etc in behind the evaporator. I ended up cutting the inside grate out of mine and just putting in some mesh so I could scoop the trash out that got in there.

 

I bought a gauge set, but haven't hooked it up to anything yet. I just recently started to learn AC systems so I'm a little paranoid. It still has R12. I had it charged less then a year ago by a decent shop and it froze before and after they serviced it. Think they gave me a copy of the pressures on the receipt.

When you say "behind the evaporator" are you talking about the side you see when you take the blower motor out? I was thinking I would optimize my fan speed first. Today I'm going to remove the blower motor, inspect the fan blades, and clean out debris. Then maybe do Jim Lane mod.

 

its the recirc door grate. I removed it and there was a ton of leaves etc in there. BTW, Is your drain working good?

 

Yea drain is working great. It leaves a huge wet spot on the ground every time it's parked. Thought I had a coolant leak when I first bought the truck. Less now since I replaced the jumper with a cycle switch. Previous owner had it jumpered so the compressor was running continuously.

I'll physically look at drain today. I removed my blower motor and everything looks very nice. No broken fan blades or debris. Think I might buy a new blower for the heck of it.

I'll look for the recirc door.

 

usually the debris will be on the opposite side from where the blower motor is

 

If left there over a period of time, the debris retains moisture, creating mold growth...Something I used to do for my customers when I could access the evaporator case through the blower resistor hole, was pick out what debris I could find, spray the inside with a biocide (hydrogen peroxide or vinegar work well), then after verifying the drain hole was clear, wash it out with a garden hose...Afterwards repeat the process with Simple Green and water again...Make double sure the drain hole is open, then button it back up...The cabin will smell fresh and have better airflow as well......Ben

 

Hey thanks, The previous owner did cut these two access panels. When I opened the large one on the right it was clean inside. I powered the blower motor removed from the truck and it works great and pulls 16 amps so I'm going to reinstall it. Aftermarket ones don't include connectors or the fan.

 

I have since taken the tree down, but the air flow was way diminished for some reason ...Mark

 

Ouch! That's not good!