New Member - Strange AC problem

[alabamals]

We have a 2001 LS with the V6. The AC blows nice and cold when the weather is not too hot or when it is cloudy outside. Summers in Bama leave little time for either of those conditions. It also only blows real cold on recirculate. I have replaced the DCCV and also tried to recharge the system on the low pressure side, but there was too much pressure to take a charge. I have tried the re-set and/or self diagnosis several times and I hear all the doors opening and closing. I have cleaned out the space between the radiator and the heat exchanger, too. The compressor appears to be working fine and I also did the test to make sure the engine fan is blowing, which it is, and it appears to increase speed with the compressor on. When the weather is even moderately hot and sunny it just can't even come close to keeping up and it doesn't even appear to blow very dry air with the humidity here when it's hot. I have also tried revving the engine higher when at lower vehicle speeds and it doesn't change anything. It does appear to do at least a little bit better when driving just on the interstate and at interstate speeds.

I am pretty good with cars, but not great with AC systems and this has gotten me really stumped. I did a search of the forum which is how I came across the DCCV common problem and the re-set and self-diagnose procedure.

If anybody has any other ideas on what the problem might be, it would be greatly appreciated. It really is tough driving it here in Alabama in the summer.

 

[LS4me]

If there is too much of a charge the system won't work correctly. I would have an A/C professional look at it.

 

[alabamals]

If there is too much of a charge the system won't work correctly. I would have an A/C professional look at it.

That may be where it ends up, but I know how they tend to exaggerate things. How do you go about cleaning out the orifice tube? What about the evaporator? Could they be part of the cause?

 

[Telco]

You can have the system charge removed, then pump a cleaning agent through the system. You do have to get it all out, and can't get any into the compressor itself though. Compressed air will blow it all out. At the same time, replace all seals. The orifice can't be cleaned (at least I wouldn't bother), but is cheap enough to replace. Replace the dryer at the same time, which should be done any time you open the system to outside air. The evaporator is essentially a large metal box like the radiator whose purpose is to allow the freon to expand suddenly (which is how it cools) while air is blown through it and is not going to be the problem here. It is very protected being inside the heater box, and about the only problem that ever develops with the condenser is a corrosion related pinhole leak or some monkeyf&&ker overtightening the hose causing it to strip threads or crack along a weld. Should a corrosion leak be found, all that is needed is a ground strap attaching it to the car's body to solve the problem. If you are concerned about an AC shop jacking you around you can pick up a professional set of gauges at an HVAC supply shop and read what the pressures are with the high and low gauges. A good set will have an ambient temp dial that will let you pick out the correct pressure for the outside temperature.

 

[joegr]

A few corrections.
The LS does not use a fixed orifice. It has a thermal expansion valve. It is not cheap to replace by any means. The entire dash has to be removed just to get to it.
The LS does not use Freon (R-12). It uses Suva (R-134a).
Also, the compressor is variable displacement. You can't correctly charge it without using a dual gauge, one for the high side and one for the low side.

 

[Telco]

Didn't know this one used an expansion valve. Quite old fashioned of it really. Of course, it also looks like cleaner should work on it so that wouldn't matter much if it can. Checked, you can get one for 20 bucks, so would still be cheap if you did the install yourself. Sounds like a pain though. But is it behind the dash or under the wiper cowl on the firewall? I know the evaporator requires dash removal to get at as it's inside the airbox. Most other cars I've seen that use an expansion valve also have it on or very near the firewall, inline with the dryer cannister.

I do tend to use the word freon like the word Kleenex though. I suppose I should use the nomenclature instead.

 

[joegr]

It's behind the dash, not on the other side of the firewall. Here's what you have to do to change it.
http://www.lincolnvscadillac.com/forum/showthread.php?76669-Dash-Board-Removal-Thread

You can call a thermal expansion valve old fashioned if you like, but it is more efficient. The only reason they went to fixed orifice plus cycling clutch on many cars was that it is cheaper. The thermal expansion valve plus variable displacement compressor makes the LS system very efficient across the whole range of operating conditions.

 

[oddball]

^+1
TEV systems, when used properly, are quite superior to fixed orifice. Home A/C systems are switching to TEV for high efficiency/multi-speed units. Cars started out TEV then switched to orifice due to cost.
Old Freon systems converted to Suva with TEVs have problems because the low side pressure is set for the best point for Freon, which is not the right point for Suva. Hence the conversion kits to orifice and the prejudices against TEVs. Adjusting the POA valve fixes that, but it appears that was just discovered about 8 or 10 years ago.

The expansion valve is on the low side of the evaporator.
Joe, does the LS use a POA valve on the high side? I have lost the online LS manual link again...

 

[joegr]

http://deneau.info/ls/
http://deneau.info/ls/s6x~us~en~file=s6xc0002.htm~gen~ref.htm

 

[Telco]

Sonuvabiscuiteater what a mess! Pics trump text every time. Thanks Joe, definitely a hire it out job.

On cars that do use orifice valves, I usually replace with a variable orifice when I change them. They work better than the factory fixed orifice valve.

 

[alabamals]

UPDATE - we took it to a garage for diagnosis and they said the compressor is bad. Not sure I buy it. If the compressor was bad, wouldn't it not blow cold at all? I mean, when it's not super hot out and the car is moving fairly well, it blows cold.

 

[joegr]

UPDATE - we took it to a garage for diagnosis and they said the compressor is bad. Not sure I buy it. If the compressor was bad, wouldn't it not blow cold at all? I mean, when it's not super hot out and the car is moving fairly well, it blows cold.

It's a variable displacement compressor. That's not an unheard of failure mode for this compressor. I assume that they saw that the low side pressure was okay, but the high side was too low. It's possible, but less likely, that the expansion valve has failed in the open position. I'd bet on the compressor instead. It's much less expensive to replace, and more likely to have this failure.

 

[alabamals]

Also, what does "bad" mean? I could possibly understand an issue with the clutch engagement or something.

 

[joegr]

Also, what does "bad" mean? I could possibly understand an issue with the clutch engagement or something.

Bad in this case means that it is not pumping as much refrigerant as it should. It's pumping capacity is well below spec. I've seen the issue, and old-timers don't want to believe that it can fail in this way. I applaud your shop for correctly diagnosing it.