Dodge Grand Caravan AC - 2001

[Diametric]

Hello!
I'm working on a 2001 Dodge Grand Caravan I have owned for about a week now. I am not getting cold air at the vents.
When I first checked the system it was low on refrigerant but still had some pressure and about 15oz of refrigerant so I assume it wasn't exposed to atmosphere AFAIK.

(I recovered the freon, vacuumed the system, then waited several hours. No leak detected. Filled with Nitrogen via low side to 150psi and left overnight. No leak detected.)

After vacuuming the system down again I added 32oz of refrigerant per the factory service manual.
A few observations.....

When I FIRST turn the AC on, the suction side aluminum pipe gets VERY cold, but within 1 minute warms back up and is no longer cold. The high pressure line gets very hot.
Pressures are good when running - 35psi and 290psi (good according to the Factory Service Manual) at the ambient outside temp of 96F. When not running, pressures are right at outside ambient.

Would you say the fact that it gets ice cold for a minute suggests at least the compressor is working or do bad compressors sometimes do this (compress the gas for a minute...then not)

Unless an evap core is leaking, I don't usually have any problem with them. Condensers even in my 35+ year old vehicles seem to keep working just fine as long as they're not damaged or punctured. Exterior fins get damaged and external crud seems to reduce their capacity but I haven't ever had a total failure of a condenser.

Just overall...is this likely to be an expansion valve or accumulator issue (or not enough info to tell)?
I looked at ACKits.com and they have competitive pricing so I'm probably going to buy what I need that I don't already have there.

[JohnHere]

Contrary to the Factory Service Manual, elevated pressure on the high side usually indicates a condensing issue. At a 96°F ambient temperature, the high side should be ~225 PSI with decent condensing.

Do you happen to know whether the condenser and fan(s) have ever been replaced?

[Diametric]

Contrary to the Factory Service Manual, elevated pressure on the high side usually indicates a condensing issue. At a 96°F ambient temperature, the high side should be ~225 PSI with decent condensing.

Do you happen to know whether the condenser and fan(s) have ever been replaced?

Hello JohnHere!

As far as I can tell neither has been replaced. But they both look good and the fans seem to operate properly.
I personally find it stunning that the FSM would publish erroneous information on the vehicles they built.
According to their information, 225psi would correlate to an ambient of closer to 80F ?
The FSM figures are also for R134a which is what I am using in it.
Would you mind telling me how you came up with your ~225 psi figure?

FSM AC Pressures Chart.jpg (57.26 KiB) Viewed 211 times

[Diametric]

I've only had this vehicle just over a week now and yesterday checked for the first time.....

Yep...REAR AC. Found lots of Oil at the expansion valve so this changes everything. Now I'm going to remove the rear evaporator to check for leaks and most likely replace the rear expansion valve and change the seals.

Nice find. Rear AC is good.

[JohnHere]

As far as I can tell neither has been replaced. But they both look good and the fans seem to operate properly.

The fans could be "tired"—that is, not spinning at full speed. They should be operating with a noticeable roar. If not, I would replace them.

Also, check that all fan shrouds are in place and that the foam insulation is still there. If it's not there or crumbling, replace it. You can often find similar material in the Insulation Aisle at your local Big Box store.

I personally find it stunning that the FSM would publish erroneous information on the vehicles they built.
According to their information, 225psi would correlate to an ambient of closer to 80F ?
The FSM figures are also for R134a which is what I am using in it.
Would you mind telling me how you came up with your ~225 psi figure?

Decades of experience
But seriously, MVAC techs generally don't use pressure/temperature charts as they can sometimes be misleading.

One way to judge whether the high-side system pressures are "in the ballpark," so to speak, are by using the following multipliers. These multipliers reportedly say that the high-side pressures should be somewhere in the area of 2.2 to 2.5 times the ambient temperature.

For instance, the ambient temperature at your location is 96°F, so 2.2x96=211 PSI; 2.3x96=220 PSI; 2.4x96=230 PSI; and 2.5x96=240 PSI. Presuming that these multipliers are valid, we could say that the acceptable high-side pressures range from 211 PSI to 240 PSI, which sound reasonable based on the condensing factor.

However, it's a given technician's judgement call. I tend to be conservative when it comes to system pressures, so I said ~225 PSI with decent condensing. The decided-on high-side pressure range can and does fluctuate, as indicated by (~), depending on whether the condenser is unplugged or partially plugged with internal debris, whether something is compromising airflow through the condenser core, whether the system has a serpentine or parallel-flow condenser, and of course the ambient temperature.

Yep...REAR AC. Found lots of Oil at the expansion valve so this changes everything. Now I'm going to remove the rear evaporator to check for leaks and most likely replace the rear expansion valve and change the seals.

Where oil is found, so goes the refrigerant.

You might also want to check the lines running from front to back. They can become corroded, degraded, and can leak, especially if they run through a wheel well.

[Diametric]

Good stuff right there!
Thank you Sir !

[Cusser]

You might also want to check the lines running from front to back. They can become corroded, degraded, and can leak, especially if they run through a wheel well.

My co-worker had a Grand Caravan from that era. He had leakage of refrigerant on the lines going/coming from the rear unit, Dodge used a hodge-podge of metal and crimped rubber hose to snake the lines back there, and the crimps leaked on his.