2000 SEL 3.8 air conditioning troubleshooting a/c

[Nox]

I tried to search for some other post on a/c...found a little, but it seems that the search tool does not seem to like the terms ac,a/c, so only got a few results even though I know I have seem more.

Anyway, Im determined to get good at the auto a/c troubleshooting. My a/c has not worked for a few years, so this could be a challenge, but dont want to spend more on the a/c that the van is worth. Wife said its me or the van if no a/c, so up against the gun here folks.

Van is still young IMO...160Kmiles. runs fine, tranny ok, ect
So here we go. Here are the symptoms:
No cold air...duh
Compressor clutch did not engage
All blower functions work fine.(including rear controls)
Blower was initially only coming out defrost. I found some post about the red vacuum line that goes to the vacuum check switch, pluged it in and now ductwork redirection to vent, defrost, floor all work fine.

Heres what Ive done. I zipped throught the schemtics after giving things a good look over. From the schematics, I did a few simple checks.
- checked a/c cycle switch-on low pressure side...it was open indicating low pressure. no doubt as probably all refrigerant gone.
- a/c clutch relay not coming on with all of the a/c controls set to on. again, Im thinking norefrigerant, but honestly not sure.
-connected low side pressure gage..saw low pressure.
-Decided to check function of clutch. I pulled the a/c clutch relay and jumpered accros the contacts in the socket. Clutch energized. So I charged one can of refrigerent. Pressure looked ok,
but....
Still hot air coming out of vents.

Incidentally, I connected the a/c clutch relay coil to 12VDC...worked fine so I put it back in.
At this point, the clutch was kincking in and out but I was not getting ANY cold air...nata bit
So now my challenge is to determine where to go from here.

How do I know if the compressor is working correctly? unfortunately, I dont have the full gage set so I cant check high pressure side. I think I should just go ahead and get the set

-I believe I will also get more refrigerant to load it up a bit more. probably will be just be killing more ozone layer as Im thinking I will have a leak. But before I got though leak testing, I want to make sure the system is basically funtion worthy.

Calling all a/c experts, or semi-experts, or anyone who has ever even tried to work on the a/c. i would appriciate thoughts on starting of the troubleshooting process. Or if there are any suggested websites that someone knows of first hand, would appriciate the URL.

One other strange thing. During troubleshooting, I hapened to notice the positive battery wire(the one that goes to the fuse box) was very hot to the touch. I got side tracked a bit trying to determine that issue, but Im confident it is separate and unrelated. I am starting a new thread for that issue"battery cable hot"

[tomj76]

When there pressure is so low that that the system will not engage, then it's not just "low" on refrigerant, it's empty.

It sounds like you could use a good tutorial on how the A/C works. There are books available at autopart stores that can provide this. You should also be able to find something on-line.

One fundemental point to remember is that the low side pressure and temperature should always be at the boiling conditions of the refrigerant. In order for the pressure to drop below the trip conditions of the cutout switch, it either has to be sub-freezing or it has to be empty of all liquid refigerant.

A/C systems require the movement of lots of liquid refrigerant. There are two reasons for this (1) the boiling of a liquid absorbs heat (in the evaporator) without changing the temperature of the liquid, which ensures efficient heat absorption (2) The amount of heat move depends on amount of refrigerant MASS (not volume) that is moving through the A/C system.

The '96 Ford Windstar A/C system with the auxilariay unit requires 54 oz of R-134A. This is about 4 1/2, 12 oz cans. Even the system without the aux unit requires something like 40 ounzes, which is over three cans.

When you only have one can of liquid refrigerant in the system, the flow rate of liquid refrigerant into the evaporator is low, and all of that is evaporated before much air is cooled. Once all the refrigerant is evaporated, then the air heats up the gas in the evaporator without cooling the air very much.

There is only one reason that your system has low refrigerant... a leak. You need to find the leak to avoid repeatedly recharging the system. If it's a big leak, you might be able to hear the gas escaping. If it's a small leak, then the easiest way to find it is to put some flourescent dye in the system when you recharge it. As the system is used the dye will leak out with the refrigerant, and a UV light will help you locate the source of the leak.

If the system leak is large, then air + water vapor is in the system. When this is the case, the accumlator/dryer has to be replaced, and a hard vacuum has to be pulled on the system before it can be charged.

Also, they recommend that you add 2 oz of PAG oil on recharge whenever the system charge is lost

A couple of links:

aircondition.com
ackits.com
autoacsystems.com
hvacr-tools.com

[12Ounce]

You must use vacuum pump to remove what you now have in the system ... air plus water plus refrigerant ... and then refill with refrigerant. I believe AutoZone now has a vacuum pump in their loan-tool program.

After you get the refrigerant/cooling system working .... the clutch staying in on its on, all the time... then you can start on the blend doors inside the cabin ... that's a whole different animal to tame!

[mark_gober]

Simply putting one can of freon in is probably not enough to make a noticable difference in the air temp. This vehicle probably handles around 48 oz. of freon if it's empty.

I agree with 12oz in that you really must remove the air/water that is in your system. If I might offer you a suggestion, pick up a vacuum pump and pull a vacuum on it. There are two ways to do this. Autozone does rent them for free (although you'll be out about $200 until you return it), or you can go to harbor freight(if one's nearby) and pick up a vacuum pump that runs off of an air compressor. I paid around $15 for mine and it'll pull a vacuum to 28.3 inches of vaccuum. I swear by that piece of Tiawan crap.

Once you've got the vacuum, you can insert the freon into the system (+plus some oil). I suspect you'll find a small leak. Hopefully it's only a small leak and you can put in a can every couple of months to get you by. Also, when you charge it, add a shot of UV dye to the freon charge. It's available in the auto parts store and will help you locate any possible leaks.

All of this is dependent on the fact of you getting an a/c gauge. Trust me, they're pretty expensive if you don't have one. You might check to see if you can borrow one from the parts store (mine doesn't have them) or a friend. If that doesn't work, I'd buy a cheap set off of ebay or craigslist. Hopefully you can make it work. I couldn't drive one without A/C.

Mark

[12Ounce]

One additional comment about evacuating a system that has water in it. The water is likely in liquid form and will possibly be "under" an oil film. To remove this water, a high vacuum must be held on the system for a long time ... even in hot weather, I like to keep the pump running for two hours, then shut off pump holding vacuum on system (hoping to get the water to move from liquid to vapor so it can be removed). The pump may be cycled several times with corresponding "off" periods to convince me the water has been removed. We're talking a day ... sometimes also overnight ... to evacuate a car system.

[tomj76]

Pull vacuum and disconnect the pump so there is vacuum in the a/c system. Drive the vehicle for a day or so to get things good and hot (aiding evap of any liquid water), and shake things up a bit. While things are hot, reconnect the pump and draw vacuum again.

Remember that the dryer/accumulater, if the desicant (an internal bag of water absorbing crystals) is in good condition, will suck up any remaining water vapor moving in the system.

Commercial A/C shops reqiure a new dryer/accumlator anytime the system is has a significant repair (replacment of a hose, pipe, evaporator, condensor, or compressor). This way they can pull vacuum one time to evacuate the unwanteds and make sure the system doesn't leak, and let the desicant do the rest.

[wiswind]

As I recall, the FORD instructions for a fully opened system, such as you are facing......requires that the accumulator be replaced, which includes the desicant.

I also agree that, if you have low/no refrigerant, that you almost certainly have a leak someplace.
You might get lucky and just need a "O" ring seal.
The most unlucky would be the evaporator coil inside the heater box inside the passenger compartment........major labor to change out.
If it is the evaporator coil, then the dye will be seen running out the water drain tube from the passenger compartment.
I had the evaporator coil develop a leak on my '96 and had it replaced.
The shop used a "sniffer" tool to try to detect leaks.....checking first around the compressor.
When they did not sense anything, they put a dye in and had me come back another day......and the dye was to be found running out the water drain tube.

For my '96......
FORD re-designed the evaporator coil and heater box which requires that the whole heater box and its contents be replaced as a whole unit......over $450 for the part, plus the labor to change out.
My shop found a after market replacement that was to the original design for $128.
Wisconsin does not permit the refrigerant to be sold to the public.....which complicates the DIY approach to A/C repair.
In my case, I was more than happy to have someone with the experience and equipment to competently diagnose and repair the problem.