a/c problem

Hi everyone. I'm having problems with the a/c in my 96 express van. Here are the facts:

it's a 350 with dual air

164,000 miles

It worked until a couple weeks ago.

It still sort of works, but doesn't blow cold now.

The compressor is turning on.

I can switch from (not very) cold to heat with the dial on the dash so I don't think it's a problem with that door that redirects air through the heater core.

I bought a $12 low-side gauge and a couple bottles of 134a.

The low side measured about 30-35 psi at first.

I tried to add a can of 134a. It sort of added some, but there's still some in the can. The low side pressure reads about 45psi now.

It's 90-100 here in chicago now.

After adding the 134a, the back is sort of marginal now, but better. My wife says the passenger side duct is cooler, but still not like it was. The driver's side ducts are still too warm, but a little better than they were.

I havn't measured the high side since I don't have the right gauge.

I have no reason to believe that the radiator area is full of leaves or something, but I havn't checked. The cooling system is otherwise working perfectly in spite of the heat.

When I added the 134a, it was at idle with the air on max and recirc.

I'm pretty sure it's not freezing up. It consistently doesn't work.

Can anyone suggest something else to check?

How does the dual air work? Is there another high/low side somewhere, like I charged the back but not the front, or is it all one system? I can only find the two ports.

The instructions that came with the gauge say that 45 psi is the limit. But that on hot days, maybe it could be higher. Is this right? What number should I be aiming for?

I've also heard that the low side pressure could drop when you run the engine at 2000rpm or so. Should I be adding 134a at 2000 rpm and make it read 45 psi at that time?

thanks.

brian

Reply to
brianlanning
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45 psi is too high

Whitelightning

Reply to
Whitelightning

Keep this in mind.... A/C works on compression. The gas gets compressed and this removes heat (makes the gas cold). If you completely fill the system there is actually less compression. Hence, a system which is over filled will not work as well.

Reply to
Todd Copeland

To eliminate the heater core/blend door as a possible cause, gently pinch off the heater hose that feeds the heater core.

How accurate do you suppose that $12 gauge is?

Is that a static reading or was the engine running, compressor engaged?

It's not like pouring in a quart of oil, unless you heat the can, it will take a good while to empty the can. You can tell the level of refrigerant in the can by observing the dew line that will form at the point in the can where liquid is separated from vapor. When the dew line is gone, the can is for all intents and purposes, empty. I also have to state that the only way to know if the system has the proper amount of refrigerant in it is to measure it in with the proper equipment.

Same temps up here in Milwaukee if it makes you feel any better.

Characteristic of an under charged system.

That leaves a large amount of information unknown. You have no way of knowing if the compressor can actually compress or whether the high side is going too high and the compressor is shutting down via the high pressure safety switch.

At 164 K miles, it's dirty. Haul out the garden hose and rinse back to front, be careful that you don't bend the fins with the water pressure.

Max and recirc are the same thing. BTW, I hope the words "sealer" or "O-ring conditioner" weren't on that can of refrigerant that you added.

Yeah, the pressure on the high side.

No. The rear AC basically "Tees" into the front system. The rear does have an actual expansion valve instead of an orifice tube.

That's pretty much BS considering that low side pressure would depend on -how- the low side pressure is controlled. IOWs, there's more than one method, and what is right for one isn't necessarily right for another.

At these temperatures, I'm seeing low side pressures well below

40*, but you have to check with the engine running above idle speed.

The faster you run a pump, the more work it does.

If you honestly have pressures that should equal cold air from the vents, there is a real possibility that you have air and/or moisture contamination in the system.

At these temperatures, it shouldn't take long before you hear the cooling fan clutch engage, does it?

Reply to
aarcuda69062

ok. I can feel a temperature difference and hear the door moving. Maybe it's not closing all the way though.

Not very. It has color bands on the gauge in addition to the numbers.

45 is the start of the yellow band. I should just go buy a real gauge set.

Idle. It didn't change at all once the system was running. I can't actually see the compressor. It's a van with that tiny hood and there's a huge airbox in the way. I can hear the click with the clutch turns on though. And I can feel a temperature difference between running and not.

I had it hooked up for maybe 10 or 15 minutes. I didn't want to go over 45psi though so I stopped at that point.

That's what it seems like to me. The pressures are up there though. Maybe it will drop to 15 with the RPMs up? I need to test this.

ok. I'll pick up a good gauge set. What should the high side pressure be? I think I remember something like 250-300 psi.

I'm not sure I could get a hose in there without disassembling the front of the van. I'll give it a shot.

sealer

So I need to pull a vacuum to get the air out? Or is it enough to vent everything to the atmosphere (I know, I know) and re-add two or three cans?

I'll have to check. Even idling, the temp gauge stays where it always does. I suspect without the fan and not moving, it would rise fairly quickly.

For the record, I hate working on full size vans. Troubleshoothing problems is like working on a ship in a bottle. I can't see most of what's in there.

brian

Reply to
brianlanning

Easy enough to verify.

Perhaps the color codes are meant for when the system is static? A normal CCOT system will cycle in between 26 and 45 pounds, it will cycle more often if there is little heat load on the evaporator (cool ambient temp) and stay running continuously in heat like we had yesterday.

You need to check the low side pressure with the engine at

1500-2000 RPM.

It would take close to 15 minutes to empty the can if you placed the can in by the hot air blast from the engine, I use a Milwaukee heat gun to speed things up when charging via can. My charging station has a heater blanket on the 30# bottle. Also, with the can connected and the valve open, you will get a false reading that is higher than actual, this is because of the pressure exerted by the can on the low side effecting the gauge reading. Once you shut off the can tapper, you will see the real low side pressure. Secondly, I've played around with the gauges like you have that come in suicide kits, the couplets are crap and often don't fully engage the service port making recharging slow to non existant and giving false pressure readings. The best couplers have a knob on them that lets you control how deep the Shraeder valve or ball valve is depressed. (back to having decent equipment)

Yes, you need more RPM. The hotter it is outside, the more pump you need.

That would be about right on a hot day. High side = ambient X

1.8 - 2.5

Trying to cover all bases. Keeping the radiator and condenser clean is cheap and relatively easy, yet it goes un-done and is responsible for many component (radiator and condenser) failures.

That isn't good. AC sealer is one product that really shouldn't be on the market. Sealer in an AC system can literally mean that you'll at some point (even now) need to replace all the AC components unless you can find someone who can successfully flush it from the system. I can't stress strongly enough how harmful sealer is. You really need to know the pitfalls of the products that you buy for your vehicles. More and more shops are buying sealer identifier tools due to the fact that they really mess up AC systems and worse, really mess up AC service equipment. If you wind up taking this truck in to have the AC fixed by a professional shop, by all means, tell them up front that the system has sealer in it, it could save you from being on the hook for a multi thousand dollar service machine.

The vacuum is absolutely mandatory. Absolutely. Air and moisture are a big AC performance killer. It would be wise to also replace the receiver drier.

Lots of money is wasted on AC repairs when all that was needed was a fan clutch or the dirt removed from the condenser. Just trying to be thorough here.

Know what you mean, got the scars to prove it....

Reply to
aarcuda69062

I'll try it when I get home. It's a lot cooler today also. We'll see if that changes anything.

Initially, I could see this, but after about 10 minutes, I couldn't. It didn't seem to matter if I had the valve open. I'll try it again today.

Thanks for the info. I really should have known this since I shun the sealers for cooling systems. I'm fairly certain it's the original compressor though. So I'm not too worried about losing it at 164k. It's about time for us to unload the van also. I wouldn't be surprised if we lost the engine or transmission shortly.

Thanks for the info. Makes me wonder why the stuff is on the market.

Is there an a/c machine designed for the home mechanic, like $500 or less, that can pull the vacuum, capture the coolant and put it back, etc? I suspect these are multi-thousand dollar machines.

Same question for abs computers. I can't totally flush the brake system on my chrysler minivans because I can't advance the abs pump. Makes me wonder whether there's a conspiracy to stop people from fixing their own cars.

brian

Reply to
brianlanning

Human nature. people will buy something that sounds too good to be true before they'll educate themselves on what it is they're buying.

Watch on e-bay, stuff shows up all the time. There is a Snap-On R-12 machine right up the road from you in Kenosha on e-bay, no bids, sitting at $99 with a jug of R-12 minus a few pounds. Not a recovery machine but it sold for well over $2000 when new 15 years ago, and they were good machines if a bit bulky. My R-134 machine was free for the taking from the Ford dealership I used to work at, it needed a few things that were easily fixed, been using it for 9 years now.

Nope, it's a conspiracy to separate mechanics from their money...

FWIW, AFAIK the DRB3 is the only scan tool that supports all ChryCo ABS functions. Can be had for a mere $8000.00 =8-(

Reply to
aarcuda69062

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