Possum-Pie

Hi, all. I've searched the net for an answer but this is a really strange problem. For the past several years my A/C works only when it's cool outside. If it's 75 deg. outside, the blower comes on icy air comes out. This week it was 95 deg. and starting the engine and the cabin blower, nothing out of the blower. not a puff of air. I put my windows down and started for home to worry about it later. Nothing for 5 min. then POOF the blower comes on, the A/C runs cool.
Other days it blows warm air for 20min, then all of a sudden gets icy. Some times the blower comes on and blows full force for a few min, then almost stops, then full force again. I can't replicate the problem for a dealer b/c they always say "we took it out no problems noted" Sometimes it does it, others it doesn't so I don't think the problem is a part that is "broken" b/c it does work sometimes. I replaced the relay in the fuse box b/c that was the easiest...no better. I'm thinking of replacing the blower motor resistor next, b/c again, not hard to do. Before I blindly start replacing things I thought I'd ask if anyone has a clue....?

ezone

So it's a blower fan problem? Well start with the fan circuits. Unplug the fan motor. Is the connector or wire terminals burned to a crisp? If so, you probably found most of your problem.

If that wiring looked ok.....then....when the fan motor does NOT run like it should....Reach up under the dash and smack the fan motor with the palm of your hand. Did that make it run? Bad motor.
Understand how it works. What it needs in order to work. Then test. Don't guess.


Fan motor must have a power and it must have a ground in order to run.

Backprobing is used to make contact with a wire terminal without breaking the connection open.

At the fan motor connector, connect voltmeter (backprobe) to one of the two wires.
Try to run the fan. When the fan does NOT run, see what you have:

White wire should be 12v+ whenever the key is turned on.

Green wire should show as grounded if the controls are set to high fan speed.

If one of the above is missing or incorrect, that gives a direction to diagnose.

Possum-Pie

OK, I haven't had time to tear anything apart, BUT
It was sitting in my garage in the dark about 90degrees, and when I started it up, it immediately blew icy cold air. No problem. Got to where I was going, parked in the sun, came out and the outside temp was only a little hotter, but closed windows- the cabin temp was like 120. NEVER cooled down on the 1/2 hr drive home cooler than barely cooler than outside temp. It can't be the freon, it blows cold when not super hot outside, but never gets cold if its an oven outside. how can temp cause it to not work?

ezone

You're gonna need to make some observations WHILE THIS PROBLEM IS HAPPENING and report what you see.


You've got the engine running, fan on full blast and AC turned on, right?

Is the interior (blower) fan running correctly? (Miserable warm air is blowing out of the vents? No air at all blowing out of the vents?)

The blower fan motor has to run correctly; if it doesn't run correctly the hvac control unit can disable the ac system.

Assuming the blower does operate correctly:

Open the hood:
Are both radiator fans running?

Is the compressor clutch engaged and spinning?

Possum-Pie

Thanks for the response...I got in my car this afternoon, it was in the garage and was 90 degrees. I started the car in the garage, backed slowly out, and it immediately blew ice cold air. Got to the school where I work, parked in the sun, came out and the same problem occured. It wasn't much hotter outside, but the cabin was an oven. I opened the windows, drove with "Max AC" on and cooled the cabin to outside temp 90 degrees, but it never blew cold, only cool. It is definately a problem with outside/cabin temp. Cabin not over 100, no problem, Cabin super hot, AC NEVER cools down. I will check fans tomorrow. Today I parked in a parking garage, outside temp 90, cabin temp 90, icy air almost immediately.
Thanks in advance,
Possum-Pie

ezone

You have to check this stuff while the problem is acting up.

Possum-Pie

Yep, thanks. I'm just hoping somebody will have recognized the symptoms. Many times with problems I've had, explaining the symptoms gets a response that someone has gone through the exact same problems and knows what was wrong. If nobody knows what's wrong, I'll have to dig deeper.

ezone

I do this all day long in real life.

I need your clear observations so I don't have to type out an entire flow chart. Again. (If the radiator fans run when you try to kick on the AC but the compressor is not, it's the relay or a clutch/coil problem)



You can search the forum, I've probably made 10k posts on AC issues alone LOL

Possum-Pie

OK,
While parked in my 90 degree garage, I started it, and it immediately blew cold air. I backed it out into the sun shut it off, and went in the house. 2 hours later, I started it again, now it blows hot air.
1. When I push the AC button, something clicks and the second fan starts and the compressor can be heard 'pulling on the engine' .
2. I see both fans running even as it blows hot air out of the AC

I've driven 40min at 2700RPM and 60MPH on full fan MAX AC trying to get it to go cold, and it takes about that long until it finally cools the cabin. BUT if I had left it in the garage it would have been so cold in the cabin that I would have had to start blending in warm air right away.
The problem definately ONLY happens if it's really hot outside. Like I said, at 85 degrees parked in the shade, it blows icy cold air immediately.
Perhaps related, perhaps not related, I'f I'm on a long trip on a highway, the AC will sometimes "ice over" meaning that I'll notice less and less air coming through the vents until there is no air at aill. Turning it off for 5min. and it will work fine again.
I did clean the cabin filter a month ago and it was fairly dirty.

ezone

You will need to visually verify the compressor clutch actually is engaged and the hub is spinning.

You realize that can nearly DOUBLE the interior temperature? When everything in the interior and dashboard is roasting at 180*+ it takes a helluva long time to get stuff cooled down enough to get some reasonable temperature blowing out of the dash vents.

40 min is too long though

That's a whole separate issue, most likely with the evap core temp sensor. It's supposed to cycle the compressor off/on around (GUESS) 36-39ish to keep the core well above freezing.

Possum-Pie

I visualized the clutch turning...plus even at its worst, it blows SLIGHTLY cooler air than outside temp air. The system is engaging and working. If sitting in dark 90 degree garage, icy air. If sitting in 75 degree parkinglot with windows up, cabin temp 120, won't blow cold air for about 20min. never blows cooler than like 75 degree air so cabin still stays hot. The blower fan is tied in to this whole thing also. If it's pleasant outside, cabin blower fan will blow granny's wig off but if it's 120 degrees in the cabin, the blower barely blows enough to move your hair. and the air out of the AC vents is warm/barely cool.