Help with AC on 2007 Mercury Mountaineer

[bdoogan]

Need help please- I'm working on my sons 2007 mercury mountaineer, 4.6 w rear ac, he bought the car used and ac didn't work, so I found out that the compressor was bad so
I replaced the compressor, condenser, accumulator, expansion valve, and rear txv to be safe not knowing what happened prior to him getting it. I vacuumed the system down for 1 hour, no problems and verified that it held pressure. Then I added 16oz pag oil ( which is what they said the system held) however I didn't account for the oil that came in the compressor ( realized that after the fact), then I charged it with 12 oz cans .. put in 3 cans and pressure was 45/270 in 70 degree weather, but system was supposed to hold 4.7lbs ( i'm thinking it's because i put in too much oil), during the filling process ac compressor was cycling on and off randomly and ac seemed to b cold after 2 cans pressures were about 35/170 but i was no where near 4.7 lbs yet.. so i kept adding freon, after the 3rd can the ac compressor never cycles off and the high side line was too hot to touch.. like burning hot, and now the ac is not ice cold but pretty cool. So, I have a few questions/thoughts ... 1-I have too much oil...if that's the reason... how do i get it out? 2nd seems like the high side switch should b shutting the compressor off when the pressure or line is that high/hot.. so maybe i have a bad switch... 3rd question.. would the ac compressor not cycling off and on cause the high side pressure to b higher like that? i'm thinking it needs to cycle off to allow the pressure to stabilize and then turn back on .. am i correct in this thinking? any help or advise would b greatly appreciated!!

[tbirdtbird]

" would the ac compressor not cycling off and on cause the high side pressure to b higher like that?"
No. That is not your problem.
You are overloaded with oil ("oil logged").
You will have to remove the comp and drain it, and flush the oil from everywhere else to get back to bare metal everywhere, then reinstall the correct amount, including priming the comp with oil,vac, and recharge.

WHO said 16 oz of oil was correct? Seems like a lot.....what does the underhood sticker say?

Was the replacement comp an OEM, reman (bad idea), what vendor did u get it from, (some vendors have crap, like 4 squeezins)

Tim the board owner has quality parts (ACkits.com) at very good prices...he has to, he is based in AZ

[JohnHere]

The specs that I have for your vehicle (with rear A/C) are 47 ounces net weight of R-134a (2.9 pounds), and 16 fluid ounces of PAG-46. So the amounts of both refrigerant and oil you charged into the system are, unfortunately, all wrong and 'way too much. I advise not running the system any more until you can make corrections.

How much oil did the manufacturer say the new compressor came with? Regardless, what you should have done is drain-out all the oil from the new compressor and measure it. Subtract whatever came out from 16 to get a remainder. Then you would have to oil-balance the system—for instance, put some in the new compressor, new condenser, and new accumulator.

A 2007 Mercury Mountaineer service manual would tell you how much oil remained in the two existing evaporators and lines, so you would have to subtract those amounts from 16 as well to get the total approximated oil amount to be installed in the new components mentioned above—that's presuming all of the oil needed wouldn't fit in the compressor. If all of it would fit in the compressor, you can put it all in there. Be sure to rotate the compressor's main-shaft about 12 times by hand before you run the system for the first time.

How do you get out the presumed excess of oil? That's not going to be an easy job now since there is no dipstick, but it must be done. In a nutshell, what you need to do is flush-out all the various components, drain the new compressor, and start again with a "dry" system. You'll need to install another new accumulator as well.

Looks like someone misinterpreted the refrigerant amount. That should be 47 ounces and not 4.7 pounds, the latter being 'way too much, as I mentioned.

The combination of too much oil and too much refrigerant is the source of your elevated pressures and poor cooling performance.

[bdoogan]

Thanks for all the info!!! I greatly appreciate it!! So what i'm gathering is that I need to flush each component ( unhook the lines and run the flush on each and then hook back up) , replace the accumulator, and start over. So for the compressor is there a drain plug for that or can I flush it out ( it was a nightmare to replace and really don't want to have to take it out to drain it unless there is no other alternative)?

[JohnHere]

So what i'm gathering is that I need to flush each component ( unhook the lines and run the flush on each and then hook back up) , replace the accumulator, and start over.

Right. It's a lot of work to get all the oil out and to re-fill it, but it's something you'll need to do before re-charging the refrigerant to specs. The oil specs, like the refrigerant's, need to be "right on" or at least very close for the system to operate properly and to last indefinitely.

To flush everything, I would remove as many components as I can because it's difficult to get out all of the flush chemical with, say, the condenser if left mounted in place. Unless it's easily accessible, you'll probably want to leave the evaporator alone and do your best to flush it in situ and to dry it out thoroughly. Here's what I said in another post:

"Blow it out thoroughly and repeatedly, preferably with nitrogen. Because the evaporator is designed as a low-pressure component, I use no more pressure than 100 PSI to be on the safe side. Lacking a nitrogen set-up, you'll have no choice but to use shop air—the dryer and more filtered, the better."

Speaking of flushing chemicals, check with Tim, this site's sponsor. He has the "good stuff" specifically formulated for MVAC systems. Whatever you do, don't use anything oily and/or hydrocarbon based, like paint thinner, which will be almost impossible to get out. And never flush a compressor with any type of solvent.

So for the compressor is there a drain plug for that or can I flush it out ( it was a nightmare to replace and really don't want to have to take it out to drain it unless there is no other alternative)?

I know the difficulty of what working on these systems can entail. I don't know about a drain plug on your specific compressor. I could be mistaken, but I doubt it has one.

Alternatively, take a look on the bottom near the back for something called a HPRV (High Pressure Relief Valve), which looks like a drain plug but isn't. Ordinarily, I don't recommend disturbing a HPRV. But if it's on or near the bottom, you might be able to remove it, drain out most of the oil (if not all of it), and reinstall the HPRV without its leaking. If it does leak, you'll have to replace it. Unfortunately, you won't know whether it leaks until you re-charge the system, run it, and then one day it suddenly stops cooling due to a low refrigerant charge. Hopefully, that won't happen, though.

Who said this was going to be easy?

[bdoogan]

Thanks so much for all the info!!'I really appreciate it!!