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Old 08-07-2010, 02:59 AM   #1
osovolante
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Question How to adjust an expansion valve.

My A/C only cools at idle. Looking over everything, I think I have something wrong with the expansion valve. I searched the google machine and here and found this from Jeh:
One thing thats not been mentioned is adjusting the expansion valve. I think r12 is about 3.5 turns from stop and r134 should be about 7. It makes a world of diference.

I found an electric fan also makes a big difference. Mine is wired to come on with the a/c and I have an overide switch to keep it on 100%.

As far as loss of cooling, you will loose some My r12 system would blow 27deg at the vents the r134a will only got to about 38 deg. thats at about 95 deg ambient on the freeway.

Tint kmakes a world of difference as well the interoir holds a ton of heat
This has piqued my curiosity, as the A/C switch was loose in the dash when I bought the car and it leaks nothing.

When I see illustrations of the expansion valve, I see two capillaries, one to sense cold at the evaporator and the other goes to the switch? With a cable? How's it work? Anyone have an illustration or diagram? Help please! August in Florida is too hot to stop to cool off.
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Old 08-07-2010, 03:12 AM   #2
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Does it get warm quickly when you are not at idle and then cold again when you return to idle?
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Old 08-07-2010, 03:22 AM   #3
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Yes. And compressor runs the whole time.
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Old 08-07-2010, 03:40 AM   #4
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I pm'ed you but this may help others.

If your system has been converted to r134a and the expansion valve HAS NOT been changed I have found it helpful to do 2 things. 1. adjust the 7/32 allen on the outlet of the valve 7 turns out. r12 was usually adjusted about 3.5 turns so it best to wind it in and then wind it back out. 2. use about 80% of the recommended charge for r12. Typical is about 2.8 lbs so 2.0-2.1 r134a is good. This is very important as well as too much or too little and they just don't get cold enough. Use the sight glass as you are filling and wait for it to clear if you have no way of measuring the amount in the system.

One thing I have recently found out is some of the replacement valves are set for r134a and if you play with the adjustment the system will not get cold enough...mid 50s to 60F

Its also important to make sure the heater valve is closed so the core isn't getting to 190 or you will never get any cold air.

Unfortunately this information can only be helpful if you have some expensive equipment floating around or at a minimum a vacuum pump and some gauges (or another way to charge the system) but
Odds are at one time the system worked and as long and was set up to run properly when it was last working, so the easiest method is to refill it with the gas of choice. ie a top off and hope for a relatively sound system.

If you have to take it apart for any reason you might as well make the investment to convert it to get it run correctly and that means fixing whatever hose or fitting leaked, replacing the drier and possibly the expansion valve.

One other important thing to try first is to just jump the pressure switch and run the compressor. If it sounds like its going to come apart and has a death rattle you might as well not bother unless you are going to do the whole thing.

Hope this helps.

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Old 08-07-2010, 03:41 AM   #5
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The expansion valve is very simple. It maintains the amount of refrigerant flow to the evap. Also called a TXV, the amount of flow is dependent on the temperature of the coil. If the evap starts to get warmer then the set point it opens up and lets more liquid in to cool it down, the opposite if the evap gets to cold it slows the flow to bring it back to the set point. Some TXV's are adustable, most are not.

If you can get the temperature of the evap coil with a thermomter where the suction line comes out you will be able to tell if the temp is moving around too much. A couple of fingers can come close to helping if you do not have a thermometer.

My guess is if there is a quick change of temp from idle you have a vacuum problem and a damper is opening letting in hot air. The evap coil will take a minute or two to change temp, not quick like 20 seconds.

As far as the compressor running all the time maybe it should be or it is low on refrigerant. The A/C should cool better at higher rpm not less.
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Old 08-07-2010, 08:12 AM   #6
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It's a dealer 134 conversion, the evaporator was replaced, I'm assuming, since that's what I think they were doing in the mid-90s. Oddly, the air is coldest when turned on after the engine being off for 5 minutes.
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Old 08-07-2010, 08:19 AM   #7
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Quote:
Originally Posted by Jeh View Post
I pm'ed you but this may help others.

If your system has been converted to r134a and the expansion valve HAS NOT been changed I have found it helpful to do 2 things. 1. adjust the 7/32 allen on the outlet of the valve 7 turns out. r12 was usually adjusted about 3.5 turns so it best to wind it in and then wind it back out. 2. use about 80% of the recommended charge for r12. Typical is about 2.8 lbs so 2.0-2.1 r134a is good. This is very important as well as too much or too little and they just don't get cold enough. Use the sight glass as you are filling and wait for it to clear if you have no way of measuring the amount in the system.
So you're saying the adjustment is inside the outlet valve? I was hoping this wouldn't be invasive.

And what about the other capillary tube? Does it screw onto the compressor switch/temp switch? What makes that work?
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Old 08-07-2010, 09:20 AM   #8
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Quote:
Originally Posted by osovolante View Post
So you're saying the adjustment is inside the outlet valve? I was hoping this wouldn't be invasive.

And what about the other capillary tube? Does it screw onto the compressor switch/temp switch? What makes that work?
Yes the adjustment is inside the valve. You have to open the system to adjust it. Odds are if it was installed years ago at a dealer it was prob set right and you just need some gas.

As to the second question I would have to look thought that sounds right.
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Old 08-07-2010, 09:45 AM   #9
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The switch maybe a thermal one where the evap temperature is sensed and it turns the compressor on and off to vary it a bit.

The problem is some where else I think if it has to do with idle and higher rpm. The stuff you are looking at does not change with rpm but pressure does.

Is it hot outside when you notice the change with rpm, as under very low fan speed and mild temps a low charge will get a colder evap. when low suction pressure occurs.

It may be overcharged too and you start to pour too much liquid refrigerant into the evap and the cooling output drops. You really need gauges to see what is going on.

What year and type is it?

You said nothing about the possible vacuum leak controlling the dampers?
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Old 08-07-2010, 12:36 PM   #10
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Quote:
Originally Posted by Jeh View Post
Yes the adjustment is inside the valve. You have to open the system to adjust it. Odds are if it was installed years ago at a dealer it was prob set right and you just need some gas.

As to the second question I would have to look thought that sounds right.
You may be right about that.

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The switch maybe a thermal one where the evap temperature is sensed and it turns the compressor on and off to vary it a bit.

The problem is some where else I think if it has to do with idle and higher rpm. The stuff you are looking at does not change with rpm but pressure does.

Is it hot outside when you notice the change with rpm, as under very low fan speed and mild temps a low charge will get a colder evap. when low suction pressure occurs.

It may be overcharged too and you start to pour too much liquid refrigerant into the evap and the cooling output drops. You really need gauges to see what is going on.

What year and type is it?

You said nothing about the possible vacuum leak controlling the dampers?
89 240, dealer retrofitted. Dampers are fine, heater valve fine.

I took it to a shop today and had the gauges put on it. Low side Schroeder valve leaks, I have tool and inserts here. When he first put the gauges on, it leaked and he walked off for two minutes (idiot), then he said it was low with the gauges on, it looked so to me anyway. It couldn't have leaked out much in that amount of time. So, I stopped at NAPA and bought some Freeze12, we'll figure it out...
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Old 08-07-2010, 07:25 PM   #11
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Just add a bit at a time, maybe two ounces then check temps. If you have a thermometer watch the suction line, the big pipe, temp right at the evap in the car. You can also watch the vent temps. Do this with the fan on high and the windows up after the inside car temp has stabilzed and started to cool. It will take 3-4 minutes between checks to get the heat out.

Get the vent temps down to 38-40 or the evap temp down to 34-36 and you are close to full. Add a bit past this but not much.
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Old 08-08-2010, 04:29 PM   #12
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Replaced low-side Schroeder valve. Put enough 134 in to check it, bought freeze12 and now figuring how to get it in there. Guess I need as adapter. I have the set up for 12, but not 134. Guess I should put in an oil charge as well...
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Old 08-09-2010, 06:06 PM   #13
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Quote:
Originally Posted by Jeh View Post
1. adjust the 7/32 allen on the outlet of the valve 7 turns out. r12 was usually adjusted about 3.5 turns so it best to wind it in and then wind it back out.
I have a brand new 240 expansion valve, NOS Volvo, that I have no reason to think was monkeyed with. I just turned the adjuster in and it went 12 turns before stopping.

I wonder how many of these were installed without being changed. What effect would this have?
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Old 08-09-2010, 06:14 PM   #14
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I thought they were factory calibrated?
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Old 08-09-2010, 06:42 PM   #15
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Looking at the valve closer I can see "134A" stamped into it. The manufacturer is Eaton.
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Old 08-11-2010, 11:02 AM   #16
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Quote:
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I have a brand new 240 expansion valve, NOS Volvo, that I have no reason to think was monkeyed with. I just turned the adjuster in and it went 12 turns before stopping.
Sorry. Didn't mean to stop the discussion dead. No clues?
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Old 08-11-2010, 01:50 PM   #17
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Waiting till Saturday to do anything else. No time during the week. But the air is cold - at idle. LOL I think maybe I was just undercharged.
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Old 08-22-2010, 04:33 PM   #18
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After much tinkering and adding of refrigerants, I have discovered that the inlet to the dryer is HOT and the outlet is merely warm. Also the compressor is making some noise. So I am assuming that my dryer is clogged and the compressor is on the way out? And the compressor cuts off going down the road because the high side pressure switch is cutting it off?

So in a normal situation, the dryer wouldn't be hotter on the inlet than the outlet? Ideas?
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Old 08-24-2010, 10:42 AM   #19
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Bump
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Old 08-24-2010, 10:45 AM   #20
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not enough oil
and so the compresser heats up and stops.
so ur better off relacing the vaLVE and the dryer, and charg the hole system
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Old 08-24-2010, 10:48 AM   #21
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and sometimes its not enough of oil or r134a. if u did not fully clean out the sytem of the old r12 it will heat up ur lines as well.. my advice full clean it out, new lines and dryer and oring. and get it chargered at a pepbys or so...
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Old 08-31-2010, 04:28 PM   #22
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Long story short - the receiver/dryer was clogged, replaced it, recharged system, WIN. Thanks for the help.
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