Any L400 A/C experts out there? Specific questions/advice.

[tonydca]

I've done some troubleshooting on my A/C (which has been blowing less and less cold over recent months) and although I've made improvements, I've come to the point where I have an L400 question and I also need some general advice from any lurking A/C techs out there.

Props to the many threads both here and on the UK site that got me as far as I did.

Background - I have an L400 Exceed (base) model without "Climate Control"; instead I have two "A/C on" switches, one on the dash for the front, and one in the middle seat controls for the rear. If an interior blower fan is on and I press either of these two buttons, I hear the compressor clutch engaging, and the engine revs speed up a tad. I understand this is normal; a pressure switch on the A/C sight glass reservoir (just forward of the battery tray) senses that there is refrigerant in the system (to prevent the compressor running on an empty/"dry" system) and engages the clutch to start up the compressor. The engine revs gets a little nudge to offset the compressor load. So far so good.

Looking thru the sight glass with the compressor running, the view is clear (as opposed to frothy like the head on beer - more on this later). This apparently means that I am either full up on refrigerant or nearly empty.

Since no cold air is coming out, I guess the latter and pick up a $55 RedTek R12A recharge kit from Canadian Tire. I hook it up as directed (dead easy to use; pretty good product as far as I can tell) and the built-in pressure gauge is reading around 60 psi with the compressor switched off, but as soon as it start up, it drops to less than 10 psi. Supposed to be 30-38 psi when compressor running according to the instructions; no info on what the correct "compressor-off" pressure is supposed to be.

So I empty in a can of R12A per the instructions, and the indicated pressure rises up to 35 psi with compressor running. Dash inside the van and Hallelujah - cold air is coming out the vents. Great!

But here is where the need for generic expert car A/C advice part comes in. With the compressor running, and a low-side pressure of 35 psi and cold air a-pumpin' out of the vents and everything Hunki-Dori, the view through the sight glass on the A/C reservoir is now constantly beer-head frothy.

Everything I've read both on the Delica websites and on the RedTek website claim that frothy refrigerant is a sign of low-refrigerant level and hard on the compressor. But if everything is running so far so good, I'm leery about pumping in still more R12A; the static compressor-off pressure reads just over 100 psi (high to me, but not sure if this is normal), and all the literature says that 30-40 psi with the compressor on is correct and that too much is even *harder* on the compressor, making it run inefficiently and more likely to blow out seals.

For now I'm just going to play wait-and-see , as I don't know if I may have a slow leak somewhere, but I'm looking for any pearls of wisdom on the normal pressure vs. sight-glass symptoms.

Now for the L400-specific question. With my now-happy-and-cold A/C system switched on, I'm reminded that the actual compressor itself cycles on and off periodically (on for say 10-15 seconds, off for 10, etc.) as I sit and wait in traffic, for example. Keep in mind that my Climate Control is not trying to maintain a constant cabin temperature; I just have the ghetto "on/off" switch, so I kind of figured my compressor would always be on when I ask it to.

Does anyone else's A/C work like this, and is there a reason for it? Is it hard on the compressor to run 100% of the time? Is there yet another temperature sensor in the system that tells if the cool side is too cold, or if the compressor is overheating or ??? I've had a boo at what L400 manuals I could find and can't find an answer, so I'm putting it out there.

Long post, but thanks for reading.

[403delica]

As for frothy sight glass don't worry about it! Red Tek has different properties then R12 and acts differently. The only thing that matters is the pressure in the system. The compressor will be on or off to adjust pressure in the system to not freeze the evaporator. If its cold don't worry about it the system will equalize high and low side over use. Diesel AC performance at idle can also be a little poor because of the low idle of the motor, something to keep in mind but most of the time you will not notice it.

If your a super keener, vacuum the system and see if it holds vacuum then add Red tek, or even better R12. Or pressurize the system with nitrogen to expose any leaks.

Sorry for the ghetto explanation!

[legionnair]

Also as an addition to the above post it will take some time for the system to normalize. When I do A/C at work I run the system at max AC for 30 min then check the condition of the sight glass.

Dustin

[403delica]

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