2000 Montana A/C problem

[chris_eitniear]

Hi all,

I've got a 2000 Montana. The A/C clutch wasn't kicking in, so I checked the freon and it was low. I got a freon (r134a) kit and about as soon as I started putting freon in, the A/C clutch kicked in.

I thought, woohoo this is going to work. I put the rest of the bottle of freon in and the gauge read slightly overcharged. The problem is that even with the freon topped off, the compressor running, the A/C still doesn't blow cold.

I checked the temp control, and when I turn the heat on it blows hot, but when I turn it back over to cold, what comes out is pretty darned close to the ambient temp.

What am I missing?

[brcidd]

How much did you put in? The cut-off point of the compressor is at 4 ozs- your system needs at least 2 lbs and evn more if it has rear air- so that would mean you need at least 2 cans maybe more...

[chris_eitniear]

Hi brcidd, and thanks for the reply. The can I put in was 18oz, and it does have rear air. The gauge that came with the kit read about 42 psi after adding freon with the compressor running. This put it slightly into the overcharge area of the gauge, so I'm a little bit leery of adding more. Should I be, or will it not hurt anything?

[1999montana]

Originally Posted by chris_eitniear

Hi brcidd, and thanks for the reply. The can I put in was 18oz, and it does have rear air. The gauge that came with the kit read about 42 psi after adding freon with the compressor running. This put it slightly into the overcharge area of the gauge, so I'm a little bit leery of adding more. Should I be, or will it not hurt anything?

I've just gone through this whole rebuild thing with the AC on our van.

While I'm not an AC professional, there is a small point of consideration that needs to be applied to filling the system; - it's called expansion.

There needs to be enough 'room' in the system for the refrigerant to go from a liquid state to a gas in order for the complete transfer of heat to occur. Too much freon and, well you just move a bunch of freon around the system.

If at all possible, can you have the system evacuated by someone with a vacuum setup? Then you can start from scratch adding the specific amount for front or rear air setup. As stated in this thread, the front only takes 2 lbs of R-134A. The rear air setup (which ours was until I converted it to front only) requires 2.6 or 2.8 lbs (as printed on the label in the engine bay). That would also require the addition of at least 2 oz of compressor oil to prevent oil starvation.

There is a better kit (well, at least IMHO) that is geared to the DIY individual. I've used a REDTEK system http://www.redtek.com/home.html# that has R-12A, a non-ozone depleting freon substitute that does actually provide better cooling than R-134A. It is available with a gauge and 6 oz cans of refrigerant, oil additive, and two levels of stop leak.

Because the molecules of the R-12A are larger, it requires less refrigerant to fill the system...12 oz of the REDTEK are equivalent to 2 lbs of R-134A.

The problem with the cans (regardless of who makes the refrigerant) is that unless you have a means to weigh the refrigerant before and after adding it, you have no accurate way to know how much has been added.

I my case, after conversion, I added 1 can of compressor oil, 1 can of refrigerant and 1 can of Pro Seal. (Each 'additive' can comes with a minimum of 2 oz of R-12A refrigerant as a 'carrier' to introduce the stop leak or oil into the system). When I began to fill the system, (it was totally empty BTW) the compressor started as soon as I added the oil charge. Then I added the R-12A can and followed that with the Pro Seal.

Then I sat back and watched to see how the system was doing. It takes a little while for the system to even out (rather like 'memory' on the highway after an accident slows the traffic).

That brought the system to a total of 10 oz of refrigerant. To 'top it off', I added one more can of compressor oil to bring the system to 12 oz.

It blows cold and works great now!

Alternatively, (and I'm not recommending this because of the environmental aspects) you could bleed some freon off to see if the vents start to blow cooler air..there is no sight glass on this system so you can't tell if there a 'bubbles' in the flow going to the condenser or not...bubbles, at least a few indicate that there is some expansion occurring.

One thing to consider is that if your reading on the suction side (low side) is approaching the red zone (outside the 25 - 30 lbs recommended) that would imply that the high side could be creeping up there too, as they are relational. Too much 'head pressure' at the compressor and the high / low switch (it's located near the accumulator; - the big aluminum can on the left frame rail) will cut out to protect the compressor.

Don't know if this makes it clearer or muddies it up for you...

[1999montana]

Just thought of something else that might point you in a different direction.

If the system was nearly depleted of R-134A, and you added 18 oz. that would only place the system on the tall side of 1/2 full. So, you could begin to introduce another 18 oz can, or if you can find it, one in the 12 oz range to bring it to a full 2 lbs.

Even if you have rear air, that would not place the system in a state where it was too low to see an improvement in the level of cool air coming out of the vents.

BUT, if your system is like ours with rear heat / air, the freon leaked out for a reason and likely there is a hole (probably multiple holes in the pipes running to the rear) and eventually the new charge will evacuate as well.

[chris_eitniear]

Added a third can of freon today, bringing the total added to 44 oz. PSI is at 35 lbs, right in the middle of the "full" range, and the AC finally blows cold.

One of the cans I added had a leak sealer in it so it remains to be seen if it will stay full.

Thanks for the help!

[rockwood84]

if the a/c system leaked then air got in the system.so when you put more freon in the air was trapped giving you a high pressure reading. now that some leaked back out you put more freon in it got colder. you either have to vent high side when you put freon in or vacuum system.