AC low side switch replaced, still no AC...

[levdeb]

Hey all!

Found the AC in our 1999 5.4 EB Expedition was not blowing cold. Grabbed some freon (with the gauge built in) and went to fill it up. Noticed the clutch was not clicking on (only the pulley was spinning), so added freon till it got to 35 as I read on this forum that if its less than 20-25 it won't kick on.

Still didn't turn the clutch. So I found a trick on here to use a paperclip and jump the lowside switch. Sure enough, the clutch kicked on. Woo Hoo! Found the problem!

Ordered a new switch and installed it today. Turned on the truck, and nothing. Still not turning the clutch on the compressor. Tried the paperclip thing again, and it turned on.

Soooo, with that said, what else could it be? Gauge reads "35-40" when I attach it to the low end port.

Thanks for any advice guys. Really appreciate it!

 

[05expedeb]

When you replaced the switch you hand to open the system that would allow freon to escape. You would have heard that. If you didn't have any pressure in that line then you had no freon in the line.

 

[levdeb]

There is a valve under the switch so nothing comes out. At least thats what I've read on this forum...?

 

[05expedeb]

Send a PM to stamp11127 as he is about the best to help you .

 

[levdeb]

Thanks! Will do!

 

[stamp11127]

I re-read your initial post...when you were adding the 134, did you have the compressor running? If not the entire low side needs to be above @29 psi before the low side switch closes.

 

[05expedeb]

According to the wiring diagram the switch closes at 43.5 psi and opens at 23 psi

 

[05expedeb]

Hopefully stamp11127 will confirm those figures

 

[stamp11127]

Those seem to be off from the chart I use:

http://www.mastercool.com/media/89660-INST_web.pdf

According to the chart the switch should still be closed at 25psi. So I'm guessing it should open somewhere in the low 20's.

 

[05expedeb]

from the 99 service manual

 

[stamp11127]

What is in the book and what I have observed are two different things. I've had systems that required jumping the low side switch while others didn't. Go figure.

The pressure at which his new switch closes really doesn't matter at this point. If he had a good set of gauges he could fill the system to spec then see if the switch has closed.

 

[levdeb]

Thanks for the info guys! I went out today and fired up the truck. And noticed the clutch is now cycling on and off when I put "Max AC" on. I hooked up the gauge (from the can) and it goes from ~40 when the clutch is off, and then down to under 15 when it kicks in. And the cycle continues...

I've uploaded a video to my personal acting website. Will post now.

 

[levdeb]

Here is the video.

ford

Thanks!

 

[stamp11127]

You need to see what the high side pressure is before proceeding. With a low side reading of 15 that usually means the refrigerant is low but could also be a partially clogged accumulator. The high side reading will let you know which one it is.

 

[levdeb]

Got it. I will rent the gauges tomorrow and see what I have. Thanks again!!

 

[levdeb]

So hooked up the gauges (both valves closed) and without the engine running I have:
Low- 50psi and High- 40psi.

Turned on the truck and the AC, and low side bounces between 20 and 40 while the high side bounces between 60 and 80...

The clutch is clicking on and off every 2-3 seconds. And warm air out of the vents.

Not sure whats next as I don't think I am supposed to add more R134 than I have in there now...

Thanks again!!

 

[stamp11127]

Sent you a few pm's.