Before diagnosing Mom's '02 Taurus warm air A/C issue I watched a video which gave advice to check the fuse, relay, refrigerant and clutch, so here's how it went...

The issue...room temp air comes from the vents when set to Max A/C and dialed to full cold, and warm air comes out when dialed to full hot. There is no sense of cold air at all.

fuse - confirmed continuous by multimeter

- with no key in the ignition one of the a/c fuse's terminals in the engine bay fuse box read 12+V and the other 0 V

- refrigerant - a quick press of the schrader valve reveals refrigerant pressure in the system

- compressor and clutch - the middle of the compressor clutch wheel turns when just a little force is applied but does not spin freely

- When the engine is on and A/C turned to Max A/C, the compressor clutch has a pattern of engaging for just over 1 second and then releases for about 5, and repeats this on 1s off 5s pattern without interruption for 5 min while I observed.

- relay - the video suggested testing the relay junction but the owner's manual doesn't show any of the engine bay relays labeled as being associated with the A/C, so that was a dead end. The clutch seems to be working ok so I'm guessing the relay is a non-issue.

As I'm testing I notice the engine light is on where I hadn't noticed it before. Called Mom and she says it wasn't on before, so I guess it just tripped. DTC code reads P1633 which translates to 'keep alive power voltage too low.' Battery failed last month so it was replaced with a brand new one from Wally's.

The only observation I can offer other than the above is that when the A/C is turned to Max and the compressor is doing it's 1s on 5s off pattern, during the 5s it's disengaged you can hear a faint scraping sound presumably coming from the compressor clutch that sounds like two very flat surfaces, one being spun and the other not, and they're barely touching. It doesn't make the sound during every 5s disengage interval, but it's definitely there. It seemed to show up more the longer the A/C system ran. The sound stops when the A/C control panel switch is turned to off.

Could this be a bad pressure switch / sensor?

I'm all ears

 

Hi Bradley,
From what you described, I would suspect the system is just low on refrigerant.
The cycling of the compressor clutch is caused by the low pressure sw doing it's job of protecting the compressor..
Do you know how to add R134A refrigerant ?
You may be able to purchase one or two cans and get things working again, ,,,,,,but the proper thing to do is find and repair the leak.
If it lasts the entire summer after you add refrigerant, you will have plenty of time to think about it.

 

If you have to add refridgerant, I suggest something having a dye so that you can hopefully see where the leak is because you're likely to add more as the refridgerant leaks out again. If you do not have gauges, I wouldn't add more than one can as you can easily overcharge the system which is not good.

 

Do you know how to add refrigerant, if not ,read up a little and get some idea of your safety first,then adding and checking so you don't overcharge the system.
This does not need to be complicated, just being safe and watching as you go.

You just DO NOT go adding refrigerant to "Fill it up". You add some allow it to stabilize and check for cooling and if not cooling yet, add some more. The ideal thing is to have a set of manifold gauges to observe the pressures. Not everyone has them so you carefully do the next best thing and that is to add a little at a time and check for cooling .If you now get cooling you stop !!!

 

When in doubt, have someone qualified check the system and do it for you. This is not something to guess at.

 

Thanks so much for the advice guys. The cycling of the compressor seemed unusual to me so I was hoping that would be a good sign as to what was happening. I've added refrigerant before but it's been so long I've forgotten most of it except for the tiling of the can. I've got a set of gauges rented from the car store so if there's a tutorial written about this I'd love to give it a look.

I'm guessing I can have the gauges hooked up and add refrigerant at the same time?

 

Anyone?

 

Connect your gauges and see if the charge is low. That is the most common problem when the a/c does not engage or cycles.

Anyone?????? Sorry if we do not sit in front of our PC's all day waiting just for you.

 

Hang on Bradley , we'll get there eventually lol.

I hesitate to post directions to add refrig because there will always be someone that decides to take a shortcut and get injured.

What part of correctly adding the refrig do you not remember ?