A/C problems continue

Edit: if someone can move this to Gen Troubleshooting that would probably be helpful.

Entering my 3rd summer with this car. A/C has never been quite right, but always got me through the summer. (Trying to keep a 10 yr old and 2 yr old comfortable)

First use this season at about 80 degrees just barely kept the air temp in the car below ambient.

I checked pressures today. It's about 65 degrees out.
Low side cycles at 5-10 second intervals from 15-20 up to 45-50 according to my gauge.

High side started off at about 100, but after 2 min. or so would work its way up to 300+ then the fan would kick on and it would settle back to about 125 before eventually ending up at 300+ again.
The air never did get cold. About the same as the ambient air temp.

Not sure if this matters, but when I turned the engine off the low side went up to about 90 -- high was at 110 or so.

I'm guessing a hack would just add more 134, but I'm afraid I may have a bigger problem here.
Any guesses?
Should I consult a pro on this one?
CAN I try adding some refrig w/o making things any worse?

Pressures seem kinda high for a 65* O.A. I woudn't add any more 134a.
Does the compressor stay engaged the whole time, or is it cutting off/on?

The compressor is cycling on/off. I said 5-10 sec at a time originally, it's probably more like 4-6.

I thought the pressures were peaking high too, but the range was so wide the average didn't seem so bad.
Wasn't sure if the right amount of 134 (assuming it's low) would bring the high and low pressure ranges closer together.

Well, normally based on your low side pres. and cutting out on low presure, I'd think you're low. But the high side just seems out of whack at 300 PSI at 65*O.A.
First off , the fan should be running on high whenever the A/C is on, so I'd look into that. In your O.P. you said fan kicked on after 2 min or so- that could be the PCM calling for hi fan to cool the engine. The fan needs to be kickin on high whenever the A/C is on or the high side will go through the roof.

Have you ever added 134a to it since you've had it?

Do NOT add more refrigerant as you as an undercharged system is not your primary problem. Adding more will peak the high side even higher.

Fix the fan first, then re-evaluate.

yes i would say take care of the fan first also. when the compressor turns the refrigerant from gas back to liquid it creates tons of heat so when that fan is working properly it will bring the high side back down which will bring low side back down also and give cooler temps.

I did add some refrig last summer.

The fan seems to be responding solely to pressure, as it kicks on consistently at around 300psi.

It's 67 out now and the engine is warm so I'm going to take some more readings and pay closer attn to the fan.

Edit:
Pretty much as I stated originally - Fan kicks on only when the high side gets just over 300 psi according to my guage.
Compressor cycles on for 3-5 sec at a time. It takes 10-12 cycles to reach 300, then the fan kicks on for 5-10 sec which drops high side back to about 100 and the process starts over.

So -- any guidance I can get on the cause of the fan not running as it should would be great.
My haynes manual appears to be of no help at all. I'll be scouring the old posts as well.

all the specific radiator fan info I can find deals with the duratec dual fan set up.

Zetec is single -- I haven't even been able to determine if it has a high and low speed.
Obviously the fan itself is functional coming on when the a/c pressure exceeds 300 psi.

I don't know if it's supposed to function at high speed or low speed during normal a/c operation.

If it has a low my guess is it could either be the low speed relay or the low speed resistor.
Am I on the right track?

During normal AC operation, the cooling fan should run continuously in the low-speed mode unless the PCM commands high-speed mode. If the HPCO switch senses excessive pressure in the high-side of the AC system, the switch sends a signal to the PCM that forces high-speed fan operation.

The low-speed fan circuit consists of the PCM, a relay in the BJB, and a dropping resistor.` The resistor is a relatively common failure. It is located a the lower driver's side of the cooling fan shroud. I'd suggest checking it first.

do the 2.0 and the 2.5 use the same resistor?
The parts sites only list the resistor for the 2.5 motor.

Edit: I measured an open loop on the resistor contacts.

Temporarily -- could I simply remove the plug from the resistor and short that connection?
If I'm thinking correctly that would cause the fan to run on high when the a/c is on. Should solve the problem until the resistor can be replaced to bring back the low speed function.
Any problems with that?

Also - I found an old thread that said the HIGH speed fan turns on with the a/c, although the low speed seems more logical. I believe that was a typo or just bad info...right??

when your high side is 300 what is the low side pressure at that time

xdetroitx said:

when your high side is 300 what is the low side pressure at that time

Click to expand...

Comp turns on when the low side is at about 15psi, turns off at about 45. It does this in 3-5 sec intervals from the initial high side ~100psi reading up to the 300.
I suppose the low side is toward the low end of its range when the high side peaks.

I did go ahead and unplug the low speed resistor and short the connector.
Fan runs at high speed with the a/c.
Pressures look much better.
It's about 60 deg right now.
Low side runs at 15-40. High side didn't get much over 100 if it GOT to 100. Vent air felt much colder than it has.

If you're still short-cycling at 60F with the cooling fan running, the symptoms now point to an undercharged condition.

sounds like the high side is now low but you will need to wait till outside temps are warmer(im not sure what the weather is where your at), i would say atleast 70-75 before you check pressures. your high side should be around 200 psi and low should be 35-40psi and vent temps should be around 40 degrees. if your vent temps are too low lets say 35 degrees then it is very possible that your evap coil is below freezing.

I appreciate the input.

Any tricks to getting the shroud out so I can replace this freaking resistor?

Also - would you expect any significant drawbacks to running the fan on high when the pcm is calling for low?

Liquid_force said:

I did go ahead and unplug the low speed resistor and short the connector.
Fan runs at high speed with the a/c.
Pressures look much better.
It's about 60 deg right now.
Low side runs at 15-40. High side didn't get much over 100 if it GOT to 100. Vent air felt much colder than it has.

Click to expand...

Sound like the primary problem here has been identified.

Next, take a thermometer(probe type) and measure outlet temp at the center vent. Have dial set the A/C Max w/ fan turned all the way up. Let it run for a couple min before taking temp. Personally I do this w/ hood closed(not sure if it makes much difference). Your reading will vary depending on the O.A. and temp inside the cabin, but I would say if you're ~mid 40's, you're all good

Liquid_force said:

I appreciate the input.

Any tricks to getting the shroud out so I can replace this freaking resistor?

Also - would you expect any significant drawbacks to running the fan on high when the pcm is calling for low?

Click to expand...

Don't know about getting the shroud out as I've never done it. Also don't know if there would be any drawbacks concerning PCM. I wouldn't think so. I suppose water temp would run cooler. If it were me I'd try to get it repaired properly as soon as I could.