A/C system questions.

[bobwhiles]

Hi,
I am adding a seperate post to my previous one re: AC Cycling as I have other general questions - hoping that some one may be able to help me understand the AC on the Ford aerostar

My quesitons are at the end of this post. I give the background of the service first.

As in my previous post I decided to rebuild the AC on my 97 Ford Aerostar 4.0l w/ AUX Rear AC

The high pressure side had a hole in the hose. I am going to do my 96 which failed do to black death. I may have already replaced the compressor on the 97 a few years back but I don't remember. I did not find signs of BD on this system.

Parts: New A/C compressor (four seasons), Rebuilt low and high hose assembly that attaches to the manifold on the commpressor, new condenser, new accumulator, PAG 46 OIL "ICE", 54 oz of 134a, severe duty orifice tubes (four seasons), new fan and new clutch. (fan was craked out and fan cluth was old). ((bought everything on sale))

Service: Cleaned fins on both evap cores, repalced all the parts above, flushed system (front and rear) and blew out with dry air. Pulled vac down to 30" for 2.5 hours. Put @13oz of oil in - 5 in the compressor, 4 in the accumulator and the other in the hoses. Set compressor on face for about 1 hour to lube the seal. Turned clutch 10+ turns by hand after hoses were installed. Ran clutch in and out after it first in enganged about 10 times.

Installed full 54oz of 134a - not sure if I needed to. The system was blowing ice cold air at 24ozs. System tag said 4.25lbs. MAX guide says 54oz and the shop manual has it at 34 or 36oz - so I went with MAX per Four Seasons recommendation - shoudl I have?

RESULTS: the clutch engaged on about 6oz of 134a and air blew cold right away. After idling for a while the high side must of gotten too high and the pressure blew off for about 3 secs and I shut the engine off. I checked the pressure on the high side and found it raising into the 300s which I thought was high (ambient temp in the high 80's).

I also noticed that I missed the locking on one of the hoses on the accumulator and could not get it back in and locked so I had to evac system, refit the hose, pulled down the vac, recharged.

RESULTS: noted the high side was rising after engine idle. Sprayed water on condenser and high side dropped. Replaced the fan clutch which was about 4 years old and the fan as the plastic was cracking. High pressure side is staying down but the clutch never cycles off.

I make a few calls to tech support (vendors) and friends and can not determine if the cluth is really suppose to cycle on and off - therefore I askt he quesiton in another post.

GUAGES: about 70 solid on the low and the high is showig about 150 to start and then goes up -

WHAT HAPPENED: I was out in Palm Desert yesterday and the front seal blew out of the compressor (I think per my son who was driving it) I can see compressor oil on the engine block to the left of the ac pump. I am assuming that the pressure side may have dumped too??


QUESTIONS:
1) what is the valve/switch that located near the muffler in the a/c hose coming off the ac pump? I noted that if you disconnect it the ac clutch will not engage. I can find no part reference to this switch or reference in my shop manual. It is a mystery to me?

2) where is the high pressure dump on the compressor?

3) is there a high pressure switch on this system? I read a post that says no. If so is it the one in q1 above or ??? Where can I get one as the only switch I can find is the cycle switch.

4) does the cycle swtih control the high pressure or just respond to the low pressure to engage the clutch only if there is enough charge - or does it work to keep system from icing over.

5) should I have stayed with a lower charge of maybe 36oz per the shop manual for this system? It was blowing cold air . . . It was suggested that the system was fully charged when it the in /out of the evap was within 10% temp of each other.

As always any feedback or help would be appreciated.
Thanks in advance, Bob

 

[BrooklynBay]

1. Are you referring to the A/C low pressure cut out switch?
2. It should be near the compressor.
3. There is no high pressure switch.
4. The low pressure cycling switch disengages the compressor clutch to prevent the system from running with an insufficient charge of freon.
5. The system will only take as much as necessary. I suspect that you either have a kinked hose or a clogged orifice valve. I know that the orifice valve was previously changed, so it might be defective or clogged.

 

[bobwhiles]

1. Are you referring to the A/C low pressure cut out switch?
2. It should be near the compressor.
3. There is no high pressure switch.
4. The low pressure cycling switch disengages the compressor clutch to prevent the system from running with an insufficient charge of freon.
5. The system will only take as much as necessary. I suspect that you either have a kinked hose or a clogged orifice valve. I know that the orifice valve was previously changed, so it might be defective or clogged.

Thanks for the help. This got me thinking about a couple more things - one of which - listd below was I could drop by the FORD dealer to check with parts.


1) No not the low pressure cycle swith on the accumulator (correct?) This switch is located just above the ac pump on the High? pressure hose. I would have to go look to be sure and can post a pic. It was suggested that this could be connected with the cutout circuit - but I don't know if that would be right. It is effected by pressure as it attaches to a shradder valve. It has to be connected for the pump to engage. Still can find no reference to the valve. Maybe a stop at Ford today might answer the question, not that they would have it as it appears that all the aerostar stuff is disappearing.

2) OK then the dump "valve" would be on the hose assembly manifold that attaches to the back of the pump.

3) OK

4) & 5) - Thanks - I am leaning more towards being overcharged now. -- If it was a restriction then I don't think air flow (cooling the air or increasing the air flow over the condenser) would lower the head pressure as much (100+ lbs). MAX recommends 54oz of 134a and the sticker states 4.25 pounds but the shop manual states about 36ozs for a system with aux rear air. I talked with a buddy yesterday and told him that at 24ozs I had cold air and now think it might be better to load maybe 30ozs and then tweak it if needed

Again Thanks

 

[bobwhiles]

OK - I think I am good. I made the trip to the Ford dealership yesterday and got the answers I needed.

The valve located off the a/c muffler is a high pressure cut off swtich. The part number for a 97' and 96' (maybe others but I only own these two years) is a 6L2Z-19D594-AA. With discount only about 22.00 + tax.

The package says vacumn switch but the parts department has it listed as a pressure cut out switch. Online I found the reference to it as a pressure switch. There is also the dump valve on the same hose assembly to release pressure if it does raise too high. This is what has happened to me on both vehicles.

I also read again the shop manual - this time taking a little more time to read for content AND DID FIND the reference to the high pressure switch. So I am now corrected.


In my post above I was guessing at the pressures for the cycling switch. There are "two" settings - One that will trigger or engage the clutch once that pressure is reached and the the other (a lower one) that if it drops down to this pressure that will cut the clutch out.

My concern in all of this was trying to figure out if there was a high pressure switch as it seemed to me that a component in the "system" was missing. It didn't make sense to allow a system's high pressure to continue to rise to a point of just dumping it off.

So the cycling switch's name is a little mis-leading - It does control a portion of the cycling - basically as to when it will engage and if the low pressure side drops enough then it wil disengage - specs in the shop manual

The high pressure cut off switcht then should cut out the clutch if the HP side rises too high. NOW I don't intend to try and test this. BUT it will be nice to have it as a safety feature instead of losing the refridgerant.

In the end, I do have the high rise in pressure issue still to deal with BUT I think that is more on the side that I overcharge the system which was pushing the pressure up with heat. I am going to go with the numbers in the shop manual this time instead of the MAX guide and the sticker on the system.

I also plan to research a little about orifice tubes. I did repalce the OEM with a high performance replacement from Four Seasons that is suppose to improve the cooling of the ac in high ambient temperatures. I am curious how it works.

Thanks Bob

 

[BrooklynBay]

Did you ask the dealer if the dual pressure switch configuration is only for vans equipped with dual A/C? They could give you a diagram of the A/C system.