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  #1  
Old 04-29-2012, 04:07 PM
scooterspal scooterspal is offline
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AC Compressor clutch cycles on & off?

My E350's AC was not working (clutch not engaging) so I added two cans (22 oz.) of r134a. Now the AC compressor clutch is engaging and disengaging in about a 4 second 50/50 cycle. Is this normal? Seems to be working. Air is cold.
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Old 04-29-2012, 09:22 PM
lsrx101 lsrx101 is offline
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Cycling of the compressor clutch is normal. However, the cycling rate sounds fast. What was the ambient temp when you checked the cycle time? What were the High and Low side pressures?

Keep in mind that the old refrigerant went somewhere. You have a leak and will be adding more refrigerant as time goes on. If the system was empty you now also have air in the system, which is not a good thing.
If the system wheezes out again you will need to address the leak, replace the accumulator and pull a hard vacuum on the system before charging it again.
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Old 04-30-2012, 09:49 AM
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Quote:
Originally Posted by lsrx101 View Post
Cycling of the compressor clutch is normal. However, the cycling rate sounds fast. What was the ambient temp when you checked the cycle time?
It was around 58 degrees out.

Quote:
What were the High and Low side pressures?
I checked the low side (fill side) and it was about mid way into the "correct" pressure according to the markings and it was going up and down with the cycling. I think that topped out at 25psi (?).

I did not check the high side. What should that read?

Quote:
If the system was empty you now also have air in the system, which is not a good thing.
Would the air cause this cycling?

Quote:
If the system wheezes out again you will need to address the leak, replace the accumulator and pull a hard vacuum on the system before charging it again.
Should I use that UV dye they sell to locate the leak? Why must I replace the accumulator?

Thanks for the help on this : )
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Old 04-30-2012, 10:48 AM
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It was around 58 degrees out.

That's too cold to try and service the AC or evaluate the pressures. Thats part of the reason for the short cycling.


I checked the low side (fill side) and it was about mid way into the "correct" pressure according to the markings and it was going up and down with the cycling. I think that topped out at 25psi (?).

I did not check the high side. What should that read?

You're using the cheapie gauge on the can of refrigerant. Those are actually little more than worthless. You need to source a manifold gauge set and check both pressures on a 70+ degree day. Many Auto Zone stores in my area will rent a gauge set and vacuum pump for a refundable deposit.

Would the air cause this cycling?
Not necessarily. Air causes the high side pressure to run too high and can damage the compressor. It also reduces the cooling since it's a non condensable gas, basically a contaminant in the system.


Should I use that UV dye they sell to locate the leak?

You can, but if the truck is newer than 1993 it came with UV dye from the factory. Go over everything with a UV light and see if anything glows.
Look at all of the line connections, hose crimps and the compressor clutch area. If you see oil or oily dirt, that's a sure sign of a leak. Spring Lock fittings are notorious for leaking and leaks are common at the compressor shaft seal.

Why must I replace the accumulator?

It's a wear item, much like your engine oil filter. If the system has been empty for any amount of time, the desiccant will be saturated with moisture. It should also be replaced if it's more than 7-10 years old. The desiccant bag can weaken from age and rupture. The desiccant is like sand and will wreak havoc on the compressor and the rest of the system.

Thanks for the help on this : )

That's why this forum is here.
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Old 05-02-2012, 04:38 PM
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Some more questions...

This AC gauge set that I rent from AutoZone. I see that it has two sides... for high and low, I assume. Is it just a matter of connecting it up and what, exactly, am I looking for? That is, what should a properly functioning system read out as for each side?

The accumulator... Do I need to go Motorcraft or is there another brand you can recommend that will do the same for less $$.

This is a purchased used 1999 van so not wanting to plow tons of money into it for the few years I may own it.

Still need to buy a UV lamp and check for the leak...

Thanks, again.
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Old 05-02-2012, 05:08 PM
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You don't need a Motorcraft accumulator. I've used ones from parts stores and they worked fine.
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Old 05-02-2012, 11:50 PM
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Some more questions...

This AC gauge set that I rent from AutoZone. I see that it has two sides... for high and low, I assume. Is it just a matter of connecting it up and what, exactly, am I looking for? That is, what should a properly functioning system read out as for each side?

Yes, High and Low. The hoses are quick connects, much like air hose connections. The basic rule of thumb for the gauge readings is:
-High Side- approx 2.5 x the ambient temp in front of the condenser.
-Low Side- Ideally, about 26-28psi.
There are lots of variables that effect the actual readings. Ambient temp, humidity, sun load, cabin temperature, engine speed, just to name a few.

The accumulator... Do I need to go Motorcraft or is there another brand you can recommend that will do the same for less $$.

Like Mark said, aftermarket accumulators are just fine.

This is a purchased used 1999 van so not wanting to plow tons of money into it for the few years I may own it.

You won't know how much the repair is going to cost until you find the leak. BTW, does the van have Rear AC?

Still need to buy a UV lamp and check for the leak...

You might be able to rent that, too. Don't forget the yellow glasses. They really make the dye stand out.

Just a note:
-Along with the gauge set, you will need a vacuum pump to remove the air from the system after fixing the leak.
-You will also need a can tap. You can't use the cans of refrigerant with the charging hose attached(They all contain sealers and other snake oil that you don't want in your system anyway). The correct cans of (virgin) refrigerant are usually on the bottom shelf and have a screw connection on the top. The tap screws onto the can and the center hose of the gauge set attaches to the tap.
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Old 05-10-2012, 10:50 AM
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Purchased a UV light and yellow glasses. Looked all over and the spot where I saw a greenish glow was around the back of the pulley on the compressor. I assume this is a leak in the front seal (?).

Is this repairable or do I need a new compressor?

One of the fill-up cans said it contained "leak sealant". Will this do anything for this leak?

To answer your question, yes it appears to have a rear blower. Air exits out the ceiling and can be controlled separately.

Is there a second chiller back/up there or how does that part work?
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Old 05-10-2012, 11:53 AM
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Purchased a UV light and yellow glasses. Looked all over and the spot where I saw a greenish glow was around the back of the pulley on the compressor. I assume this is a leak in the front seal (?).
Is this repairable or do I need a new compressor?
You need a compressor. The seal "can" be replaced, but the success rate is only about 50% (or less in my own experience). Wear in the front housing causes too much deflection in the compressor shaft, which causes the seal to fail.

One of the fill-up cans said it contained "leak sealant". Will this do anything for this leak?
The only thing AC leak sealer will do is contaminate the system and lighten your wallet. It's garbage.

To answer your question, yes it appears to have a rear blower. Air exits out the ceiling and can be controlled separately.
Is there a second chiller back/up there or how does that part work?
There is a second evaporator, metering device and air handler in the rear. The front and rear systems share the compressor and condenser.

The problem you are faced with now is that you have no idea how much oil is in the system. (originally 15oz, I believe). Some leaked out with the refrigerant, some will be lost in the old accumulator, some will be lost in the old compressor and some will remain in the system after you replace the necessary parts. There's really no good way to estimate how much oil to add back.
The "correct" way to proceed would be to flush the system dry (a major project on your dual system), then add the specified amount of oil back during reassembly.
If you replace the compressor and accumulator, 8 ounces will probably get you in the ballpark.
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Old 05-10-2012, 04:16 PM
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Quote:
The "correct" way to proceed would be to flush the system dry (a major project on your dual system), then add the specified amount of oil back during reassembly. If you replace the compressor and accumulator, 8 ounces will probably get you in the ballpark.
What exactly do you mean? Is this the vacuum pump or something else and why does the dual system make this more complicated?

Thanks!
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Old 05-10-2012, 04:22 PM
lsrx101 lsrx101 is offline
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Normally, you would remove the orifice tube then solvent flush the lines, condenser and evaporator to remove the old oil then blow them dry with compressed air.
It's much more complicated on a dual system because of the expansion valve on the rear unit. It would have to be removed to flush the rear lines and evaporator. Major disassembly of the interior is involved.
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Old 05-10-2012, 04:40 PM
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Being a 1999 vehicle and my personal need for AC not that critical do you suppose can I get away with:

1) using the vehicle as is and refilling the system with a couple of 11 oz. cans each season?

or

2) vacuum the system, replace the compressor, accumulator, add 8oz of oil, refill and hope for the best?

BTW: what is the expansion device and do I need to replace that... around $5.00
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Old 05-10-2012, 04:56 PM
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Your van will use an orifice tube in the front and a thermal expansion valve in the rear. It would be a good idea to replace the orifice tube. It is located in the evaporator inlet tube (smaller tube). Be sure to replace the orings in any fitting that you disconnect.

2) vacuum the system, replace the compressor, accumulator, add 8oz of oil, refill and hope for the best?
That's what I was suggesting earlier.
Just to be clear, you pull a vacuum on the system for 30 minutes before adding the refrigerant. You don't want to have any air in the system.
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Old 05-10-2012, 05:06 PM
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This oil... this is not the oil in the compressor correct? Was watching a video just now and the guy was removing and adding clear oil to the back of a car's compressor he had on the bench.

This is oil flowing with the refrigerant? How do I add that and where do I purchase it?
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Old 05-10-2012, 06:01 PM
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Yes, it's the compressor oil. The oil in your AC system circulates with the refrigerant. There needs to be some oil in the new compressor so that it does not run dry when it is first started.
Some compressors have an oil sump, much like a small engine. The FS-10 in your van does not.

I usually pour about 4 ounces down in the suction line after installing the compressor, then turn the compressor by hand about 20 times. That's the big line that comes off of the accumulator. This prevents having the oil spill back out while installing the compressor.

Many new compressors have oil in them from the manufacturer. I usually drain it out and start fresh.
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Old 05-10-2012, 06:01 PM
 
 
 
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