Dash AC-Charge Ports at Front of 2004 Signature

[Lee Smith]

I recently bought my coach it does not appear that the dash AC has any charge left. I bought a set of gauges and hoses so I can check soon. The condenser fan does not turn on nor does the compressor engage.
I plan to vacuum the system and re-charge my 2004 Signature Conquest today. 
There are no hose connections in the front (generator compartment). Can hose connections be added or is it necessary? Here is a picture:

On the rear, there are two sets of hose connectors. One is at the compressor and the other set is just to the right of the compressor. Which set of connections would be best for the vacuum process? Here are pictures:

 

Also, I bought 11 ounces of the PAG 100 oil. 3 ounces is in a pressurized small can with a hose connection outlet. The 8 ounces came in a pour out bottle with no connection or pressure. Two questions:
1. After excavation is done, what is the recommended sequence to add R134 and PAG 100 oil?
2. How do I add the liquid pour bottle of PAG 100? 

I very much appreciate your help and comments.

[FLynes]

Here's a great link showing how to do it. There's an alternate way, but it involves taking the compressor off of the vehicle and filling it:

 

[Guest Ray Davis]

I'm certainly not an A/C expert but I believe most of your compressor oil is still in the system and 3 oz may be plenty to add.

Some compressors have a screw in plug sort of like an engine oil drain plug if that plug is accessable you can use a small funnel to pour oil directly into the compressor. 

Hopefully someone with more knowledge will chime in.

Also, I wouldn't attempt to add more ports, more is not necessary IMHO.

[Old Dog]

In your write up I didn't see any mention of finding and fixing the leak/s. You could be doing this again in as little as 2 weeks.

[Lee Smith]

New Question:
My system had a total R134 leak out. I suppose from years of sitting and no AC running.
I will do a total re-charge after vacuuming the system.
I cannot find any way to check existing oil in the compressor. 
Any thoughts on this are greatly appreciated.

No, I do not know about leaks.
I have currently put a vacuum on the system and am waiting an hour to see if it holds. If it does hold, then I will vacuum the system for at least 45 minutes.
 

[vito.a]

Wow, looks like you have a Detroit Series 60.  Nice find. 

I use the connections on the passenger rear side to service the A/C.  Hang your gauges on the door hinge mechanism. 

After you pump it down see if it will hold the vacuum for an hour or so.  Then add up to 4 pounds of R134a.  There are different approaches to adding oil.  Many will tell you that very little oil leaked out, so don't bother.  The purists will tell you to clean out the system and/or install a new compressor.  I would add 3 pounds of R134a and see what the temp is on your dash vent while on high.  Watch the high pressure side because it will get too high while sitting static.  Some guys will place a large box fan in front of your condenser.  The condenser on the Signature is mounted to the firewall just behind the front axle.  You can also periodically spray the condenser with a hose.  The built in fan will not keep up while you are sitting static.  

Hope this helps.

[Gary Cole]

There is no way to determine how much oil is left in the system without removing the components and draining the oil. Might be able to drain the compressor in place. Draining the condenser is not too much of a challenge. Draining the evaporator does not look like fun. Your going to be replacing the accumulator as it has a filter and dessicant so that amount is the only oil which you would add.  If  you had a very slow leak then you probably don't need to add oil to account for the other components.  Too much oil will reduce the efficiency of unit. Not a good thing because the performance is not that great as is. 

Edited July 28, 2022 by Gary Cole

[TimSpencer]

First I would search for the leak. Connect your new set of gauges to the connections near the compressor. Try to determine low pressure connection and high pressure connection(blue and red hoses respectively) high pressure hose will go to condenser and low pressure hose to the evaporator(front of coach). Pressurize the system with dry Nitrogen not Air from a compressor, not CO2, and absolutely not O2. First two will add moisture to your system(bad) last one will cause a large explosion.  With 100-150# of pressure from your nitrogen. You can use a dish soap and water in a spray bottle to look for leaks. Spray every connection and if it leaks you will see bubbles. Release nitrogen and fix leaks retest if necessary. Once leaks are fixed connect vacuum pump to yellow (center hose).  Open all valves (including valve on vacuum pump) and start pump. Watch gauges and both should start to go into a vacuum in the gauges. Get it to the lowest point on the gauges (29.9”WC) may take a few hours. Once you are at or near the pin. Close all valves on gauges and have cold one. Pressure should hold. After an hour or two if it’s good you can start to add oil and or refrigerant. Oil can be “sucked” into the low side fitting of compressor. Yellow hose in oil container or if using pressurized can connect to yellow hose and only open blue side valve and oil end up in suction portion of compressor which is open to the oil sump. Be careful not to suck “air” into the system. Then you can start to add refrigerant. I would close all valves and add refrigerant to the high side, red hose. If you are sure of charge amount try to add all of it at this time. Close all the valves again and start the engine be sure you have max air flow across the evaporator(dash) coil and condenser coil(usually near radiator) fan for condenser maybe needed. Turn system to full cooling and monitor gauges and operation of the clutch on the compressor. Now that you have pressure on the system it should lock the clutch and turn the compressor. Monitor the pressures and temp of the air out the dash. Convert pressure to temp(numbers in multiple colors on gauges). For this type application you want 40*F on the blue(cold) and 100*F on the red(high) side. R134a roughly 35#,125#. 
only other suggestion would be to replace the “filter/drier” if the system has been open (leak) for an extended time.  It may clog up once it’s been running for a while if there are to many contaminates in the system.  I would also be sure you have a separate and specific fan for the condenser coil as this seems to be a common issue with these systems. 

[TimSpencer]

Take your time and you will be able to get the system running it’s best. Seems daunting but each step is not very difficult. Air conditioning/refrigeration has been my trade for 30+ years now. Post back with any questions or observations. 

[Lee Smith]

Okay so this is going well thanks to all of the very good information and advice I have received.
Based on advice from Vito, I was able to obtain my coach data card and easily identify my OEM compressor. Enormous help!
I found a new OEM Sanden compressor for $319. 
I did the vacuum hold leak test and the system held the pressure fine.
I am thinking that now is the time to replace the compressor which sounds like very good preventive maintenance and also the way to get the replacement oil correct using the old compressor measurement method. 
I was able to download the Sanden service manual which is very detailed on all steps.
Any advice on removing and re-installing the compressor on the Detroit Series 60 engine will be greatly appreciated.
Please share your thoughts and advice.
Thank you.
 

[trailmug]

PAG oil holds onto moisture.. if you have an inkling to replace the compressor, do that (and get an O ring kit) and definitely swap the receiver/dryer. That should mean you're good on oil unless you flush lines, then I'd add a few ounces for the long lineset

If you replace the receiver/dryer, I'd cut it open. Check out what mine looked like (and what led to a flush). 

[georgecederholm]

8 hours ago, Lee Smith said:

Any advice on removing and re-installing the compressor on the Detroit Series 60 engine will be greatly appreciated.

Our 2005 Exec is likely similar, although there are often lots of variables. I had difficulty removing the large hose connections on the compressor itself and had to use an open-end wrench and then hammer the end of the wrench to loosen. Couldn’t get enough leverage otherwise. You might need a step stool to get high enough for better access. Other than that, pretty straightforward. Take pictures of the serpentine belt routing to make sure you can get it back in place properly. Could be time to change the belt if old. You might have to cut and splice the wire for the clutch if the connector is different. I think the torque spec for the compressor bolts is 30 foot-pounds.

Edited July 29, 2022 by georgecederholm

[Gary Cole]

Thanks for that picture Rob. I have been using the term accumulator and receiver/dryer as if they were the same. I imagined that smaller systems typically combined the 3 functions.  I don't see a dessicant pack or a filter in your picture? If there is any filtration going on then it is solely by gravity and the perforated screen. 

[TimSpencer]

This is a very common automotive/truck filter/drier receiver. Usually has a treated pumice stone as the filter/drier. 

[trailmug]

As I understand it, receiver is on the high side after the condenser, accumulator is on the suction side before the compressor. Both are used to store desiccant (pretty sure it's in a bag below the screen) and provide rudimentary filtering. I've heard a dedicated inline filter is better but if you have chunks floating around, I guess you've probably already lost 😁

Also you can't see it in that photo, but the screen with the big holes sandwiches a smaller screen, maybe the coarseness of a window screen or a bit finer.

Edited July 30, 2022 by trailmug

[trailmug]

I would put money on finding a leak at a hose crimp (Monaco field assembled the hoses with a manual crimper.. my own odds with a manual crimper are about half of them failed.) Gates brand fittings were much more reliable in my experience when using a MasterCool crimper. The only hose+fittings you can find these days that are engineered as a system are reduced barrier hoses, so you're kind of on your own to try it and see what holds. I had ParkerStore make me a compressor discharge hose with Tube-O and MIO fittings (for an arm and a leg) to reduce the number of crimps I had to make. Would absolutely do that again. Figuring out all the industry terms for the various fittings was a treat, especially since it's not the same across brands.

[TimSpencer]

10 hours ago, trailmug said:

As I understand it, receiver is on the high side after the condenser, accumulator is on the suction side before the compressor. Both are used to store desiccant (pretty sure it's in a bag below the screen) and provide rudimentary filtering. I've heard a dedicated inline filter is better but if you have chunks floating around, I guess you've probably already lost 😁

Receiver in on the liquid line and will be high side pressure. It stores “excess” liquid refrigerant.  As the load on the evaporator goes up and down the metering device will back up the liquid into the receiver. The filter/drier also works better on liquid refrigerant so the automotive industry incorporated all of these into one device for packaging issues. The accumulator will be on the suction line, low side pressure. It’s a tank designed primarily to protect the compressor from any liquid refrigerant or oil slugging the compressor and ruining the suction valves of the compressor. This item is not always used. It’s very common on Heat pumps but straight cooling systems it’s not universal. Automotive units use desiccant in the accumulator but not always. The desiccant is a solid formed “brick” or pressed collection of treated pea gravel looking material.  Device usually has a fine screen on the leaving side to collect large particles. 

Edited July 30, 2022 by TimSpencer

[trailmug]

One last suggestion if you are going to swap the compressor, there are holes in the mounting bosses for penetrating oil. Use them, I snapped a bolt and had to take the thing off with a chisel and saw.

[Lee Smith]

I have decided to replace the belt tensioner, the dryer and the a/c compressor. Detroit Diesel Series 60 14.0L.

The belt tensioner is DD #23527565 with a cross reference to Gates 38501.
The original belt tensioner came off okay and the new Gates fits correctly. Now I need the know the bolt torque for the new tensioner.
I appreciate any help here.

In the meantime, I am working on the compressor replacement. I bought a Sanden OEM replacement and found a real good Sanden manual to cover the new installation including detailed instructions on how much oil to use.
 

[trailmug]

Might be able to use standard bolt torque for the fastener size/grade. I've always gone with "snug" for stuff not involving a gasket.

Are you planning to leak check before the repair? Maybe put a 134a vapor charge on it and go around with a sniffer? Sometimes stuff will leak under pressure but not under vacuum.

[TimSpencer]

Refrigerant is terribly expensive to use as a test gas and the cost for a “sniffer” leak detector might be excessive for a one time use. Easier to pressurize with nitrogen (you will need to buy a regulator) and use soap bubbles to find leaks. Nitrogen can be found at welding supply stores or places like AirGas that sell all sorts of compressed gases. Deposit for a tank, return tank for deposit and contents are very cheap. Regulator can be found online for a good price too. Pressurize with nitrogen, spray hoses and connectors with soap bubbles and look for signs of leaks, fix leaks, check repairs. Much simpler and straight Forward. 

[Lee Smith]

I replaced the dryer. Very little oil (maybe a thimble full), but what is there looks clean. Cut the bottom off: 
Here is a picture:

Next, I removed the existing compressor. 
1. Coach data card said to use the Sanden U4756. I bought the interchange cross reference Sanden U4475. 12V. Compressor Family SD7H15. 300cc factory oil charge. Displacement 155.0. Problem is that the ac compressor clutch grooves do not match the existing and replacement belts. Cannot use.
2. Existing compressor removed:  Turned out to be a U4420. Too bad it was impossible to read the label until the compressor was removed. 12V. Compressor Family SD7H15. 200cc factory oil charge. Displacement 155.0. Micro amount of clean oil came out. Not enough to measure. Apparently, this is the correct compressor as the groves in the clutch pully exactly match the existing belt and the replacement belt I bought. Also, same belt grooves as the alternator.

Both compressors are from the same compressor family with same displacement and the same voltage. But the belt grooves are a deal breaker.

I am very perplexed by no apparent leaks in the existing system and no oil in the existing compressor. The existing compressor turns clockwise manually with no problems. No sign of debris at all. 

I bought the coach from Canada, and it does not appear the dash ac was used at all. No refrigerant at all in system. As previously noted, my vacuum leak test held for one hour. I did notice a bad connection at the dryer consisting of exterior rust where contact was made with the O-ring. I cleaned it up, coated the new O-rings with oil and reconnected the lines.

I am thinking of putting the existing compressor back in with a full 200cc oil charge, adding enough oil per the Sanden manual, vacuuming the system for one to two hours and then adding refrigerant.

Opinions will be very much appreciated.
Thank you,
Lee

[TimSpencer]

The oil is in the system unless it leaks out. Same as refrigerant. The oil is likely in the evaporator and condenser coils. These systems have a small amount of refrigerant and if there is a small leak it leaks 24/7 so over a long period of time it will be gone. Vacuum check for small leaks is not very accurate unfortunately. I would reuse the compressor and a new charge of oil, replace the receiver drier, and accumulator if equipped. I would pressure test with nitrogen ( nitrogen also helps dry the system) leak check then evacuate with a proper vacuum pump. I would try to get to the lowest reading on my gauges ( unless you have a micron gauge). Charge system when vacuum is at lowest. Run the unit and check temps and pressures. Hoses and orings are likely suspects for leaks. 

Edited August 6, 2022 by TimSpencer

[trailmug]

Non-use can lead to drying/leaking of the compressor shaft seal.. explains the missing refrigerant but not the dry crankcase. I ended up needing 400cc oil in a flushed 45' system (new condenser, compressor, receiver) to get the right amount of oil in the compressor per dipstick method (I didn't use the RPM/drain method because getting to my compressor is a bear. If you do the RPM and drain method, do the math on the pulley sizes because the spec is for compressor RPM, not engine RPM). Wouldn't surprise me if it was low on oil from the beginning. FYI, took me 2 hrs of vacuuming after flushing to get a steady vacuum per micron gauge.

I'd be tempted to start with 200cc in the crankcase. I believe the Sanden manual has suggested oil make-up amounts for various replaced components. In my experience, the long suction line (and what I presume is oil pooling in it) tends to make the low side pressure at the rear service ports lower than what the evaporator saturation pressure would give you (15 PSI lower for me). Opening the compressor clutch circuit would cause the gauge to immediately rise to the expected sat pressure.

At the risk of being too verbose, I was able to feed the entire 4lb charge as liquid into the high side of the evacuated system (evap fan running). Super fast and easy that way. If you don't have a bulk tank, you can get your 609 certification online at Mainstream Engineering (I did) 🙂

Edited August 6, 2022 by trailmug

[Lee Smith]

I just ordered the U4420 ac compressor which matches what I removed. I now know to check the belt grooves when ordering a compressor,
My engine belt requires 8 grooves. The one listed in my Monaco data card only had 6 grooves. Mayb it was for the stock Cummins engine. I have the Detroit 60 14.0 L.

I tend to agree on the "low oil from the beginning as to why no oil was in the compressor. Good thing the coach spent a lot of time in Canada.