charged a/c, low pressure jumped equal to high pressure

[chief455]

so, after changing some hoses and vacuuming the system, recharged my a/c, high side was ~140, low side around 35, clutch cycling, cool interior, all good.
After doing other work, restarted car - high/low pressures were equal at around 100 and a/c just ran, did not cycle the clutch.
thinking something went bad, started searching the web. Then we started the car again, the a/c is cycling, and high side is 120 and low is 30 = working again!
what happened that caused high/low to be equal for that moment?
What would be bad to cause high/low pressures to equalize?
It will happen again, is my concern.
thanks.

[fastblackmerc]

so, after changing some hoses and vacuuming the system, recharged my a/c, high side was ~140, low side around 35, clutch cycling, cool interior, all good.
After doing other work, restarted car - high/low pressures were equal at around 100 and a/c just ran, did not cycle the clutch.
thinking something went bad, started searching the web. Then we started the car again, the a/c is cycling, and high side is 120 and low is 30 = working again!
what happened that caused high/low to be equal for that moment?
What would be bad to cause high/low pressures to equalize?
It will happen again, is my concern.
thanks.

Did you change the orifice tube?

[chief455]

Did you change the orifice tube?

I don't know
I have a mechanic, not my hands.
which is it, and why do you ask?
thanks!

[fastblackmerc]

I don't know
I have a mechanic, not my hands.
which is it, and why do you ask?
thanks!

The old one could be causing your problem.

[chief455]

The old one could be causing your problem.

http://www.carid.com/2004-mercury-ma...orifice-tubes/

have not found diagram showing where this goes?....

[fastblackmerc]

Once again, Google is your friend..........

http://www.buyautoparts.com/howto/AC...tem-Layout.htm

http://www.freeasestudyguides.com/ac...fice-tube.html

If you don't do your own work, ask your mechanic.....

[chief455]

Once again, Google is your friend..........

http://www.buyautoparts.com/howto/AC...tem-Layout.htm

http://www.freeasestudyguides.com/ac...fice-tube.html

If you don't do your own work, ask your mechanic.....

great search results, thanks!

[jparrie]

so, after changing some hoses and vacuuming the system, recharged my a/c, high side was ~140, low side around 35, clutch cycling, cool interior, all good.
After doing other work, restarted car - high/low pressures were equal at around 100 and a/c just ran, did not cycle the clutch.
thinking something went bad, started searching the web. Then we started the car again, the a/c is cycling, and high side is 120 and low is 30 = working again!
what happened that caused high/low to be equal for that moment?
What would be bad to cause high/low pressures to equalize?
It will happen again, is my concern.
thanks.

Any time the compressor is not running, the high/low pressures will begin to equalize. You need to determine what was causing the compressor clutch to not engage.

I had my system do something similar not too long ago, turned out to be a module that is mounted on the firewall under the hood. There is a how to on this site that shows how to repair it. Seems to be pretty common, bad solder joint on the board. A few minutes with a soldering iron and all was good.

As I recall, it was a bit of a pain to get it off the car and on the bench.

[chief455]

Did you change the orifice tube?

found it in the hose, pretty full of crap.
It seems my compressor is likely coming apart, causing random issues.
Time to replace some parts. Thanks for the quick tip!

[fastblackmerc]

Any time the compressor is not running, the high/low pressures will begin to equalize. You need to determine what was causing the compressor clutch to not engage.

I had my system do something similar not too long ago, turned out to be a module that is mounted on the firewall under the hood. There is a how to on this site that shows how to repair it. Seems to be pretty common, bad solder joint on the board. A few minutes with a soldering iron and all was good.

As I recall, it was a bit of a pain to get it off the car and on the bench.

I believe your referring to the Blower Control Module, aka BCM. The BCM controls the fan speed. It has nothing to do with the compressor.

[RF Overlord]

It seems my compressor is likely coming apart,

Check very carefully...what you're seeing may be desiccant from the receiver/drier (accumulator). It's fairly common for those to disintegrate and clog the orifice tube.

...and a whole lot less expensive to replace than the compressor.

[fastblackmerc]

Check very carefully...what you're seeing may be desiccant from the receiver/drier (accumulator). It's fairly common for those to disintegrate and clog the orifice tube.

...and a whole lot less expensive to replace than the compressor.

Agreed!

In the picture looks like desiccant. If it was the compressor you'd see metal bits and pieces.

[fastblackmerc]

Agreed!

In the picture looks like desiccant. If it was the compressor you'd see metal bits and pieces.

Either way you'll need to flush the system and should probably replace parts.

[chief455]

Check very carefully...what you're seeing may be desiccant from the receiver/drier (accumulator). It's fairly common for those to disintegrate and clog the orifice tube.

...and a whole lot less expensive to replace than the compressor.

Great advice, thanks!

Agreed!

In the picture looks like desiccant. If it was the compressor you'd see metal bits and pieces.

We thought the same thing - but much of it sticks to a magnet.

Either way you'll need to flush the system and should probably replace parts.

exactly. I hated to spend the money, but just freon refill costs $64, so I went for a new compressor, accumulator and orifice tube. Do it all once.

[fastblackmerc]

Great advice, thanks!

We thought the same thing - but much of it sticks to a magnet.

exactly. I hated to spend the money, but just freon refill costs $64, so I went for a new compressor, accumulator and orifice tube. Do it all once.

Magnet? Most of the A/C system hard parts are aluminum.