Air conditioning problems

[Concrete cowboy]

2013 cxu 613 .

Need some help ..a.c. blows good and cold at idle..62 degrees  . As soon as you start driving down the rd ..its starts warming up..82 degrees .i cleaned evaporator install new cabin filter ..checked freon and that was good ..recirculation door works properly..cleaned bugs out from condenser from fan side forward ...cleaned and checked everything that i can think of .checked low side by touch and its cold and dripping water like it should...and its cold going up to metering device ...inside blower motor is doing its job like it should ..any help 

Thank you for your time 

[Geoff Weeks]

9 minutes ago, Concrete cowboy said:

2013 cxu 613 .

Need some help ..a.c. blows good and cold at idle..62 degrees  . As soon as you start driving down the rd ..its starts warming up..82 degrees .i cleaned evaporator install new cabin filter ..checked freon and that was good ..recirculation door works properly..cleaned bugs out from condenser from fan side forward ...cleaned and checked everything that i can think of .checked low side by touch and its cold and dripping water like it should...and its cold going up to metering device ...inside blower motor is doing its job like it should ..any help 

Thank you for your time

1st 62 deg is not good at idle unless it is 125 deg or hotter outside.

 Unless you removed the refrigerant, weighed it and put it back in, you can't have checked the amount in the system. Pressures in the system tell you the temp of the refrigerant, and therefore how well it is moving heat, but not how much is in the system.

 Until the amount in the system is known to be correct by weight, it can be impossible to diagnose further problems.

Poor condenser performance is often a problem on older systems, the condenser is low an out front, and subject to all the debris and chemicals the road can throw at it. 

 1st order is to leak check the system, as it still has enough in it to operate. Go over the whole system with a good sniffer. pay special attention to the compressor shaft seal.

Have someone raise the engine speed to around 1500 or so while you watch the compressor clutch,  may be put a white mark on the face of the clutch and pulley and watch to see they are turning at the same speed (clutch not slipping).

 If you can't find a leak, the clutch is not slipping, then recharge with the measured amount the system calls for, and start looking at the heat loss across the condenser.

gas should enter hot (almost burn you but exit warm, just above ambient. You should be able to run you hand along the tubes from top to bottom and feel a steady drop in tube temp, no cold spot and no sudden change in temp.

 Most system see a condensing temp (pressure) of about 30-40 deg over ambient temp, on the hottest days, the closer the temp of the refrigerant leaving the condenser the better it will cool. My truck would see temps between 15-20 deg above ambient temp on the exit of the condenser, but I over sized the condenser from stock and was running R 134a in an R 12 system, still it would get the evaporator cold enough to trigger the frost switch (32 deg) with outside temp of 95 deg while running down the road.

I suspect your system is low, but without pressure and temp readings I can't tell you if that is even a possibility. Low refrigerant has a tell tail pressure readings, so it can say it is low, but not that it is filled to the correct amount, that can only be done by weight to any accuracy.

[Concrete cowboy]

The system called for 3.3 lbsand thats exactly whats in the system as for the clutch slipping ...idk for sure that it is or isnt ..but will do what you said about putting a white mark on clutch and watch what it does .....thank you for all advise and will get back to you on what i find out 

[Joey Mack]

Isnt the clutch on that model internal?  If its the Sanden that i have seen before, you wont see the clutch engage. G.W. makes some good points though..  was the expansion valve replaced recently.

[Geoff Weeks]

3 minutes ago, Joey Mack said:

Isnt the clutch on that model internal?  If its the Sanden that i have seen before, you wont see the clutch engage. G.W. makes some good points though..  was the expansion valve replaced recently.

I wasn't aware of any trucks that were "clutchless" compressors (variable displacement) that turn the shaft all the time like some cars, but stand to be corrected on that. Those types have a control valve in the compressor that move the swash-plate to 0 instead of a clutch. Big pain in the rear. All others have a clutch on the front that can be observed.

 Sanden's I'm aware of all have clutches, with it turned off the center bolt will not spin with the pulley. 

If it is clutchless than there have been a lot of problems with the control valves in the compressor not moving it to high displacement. You'll see low high pressure and high low pressure.

 The the charge is known to be correct by weight, then we can move on to pressures and temp readings. It is possible the Tx (if used) is stuck in its lowest flow position, but my experience is that is unlikely, not impossible, but not the 1st place I jump to. Does this truck have a bunk unit also? 

 

[Joey Mack]

Actually, there is a clutch, it just isn exposed. It is behind the pulley..  i dont care for them.  Im with you G W.

[Geoff Weeks]

2 hours ago, Joey Mack said:

Actually, there is a clutch, it just isn exposed. It is behind the pulley..  i dont care for them.  Im with you G W.

I've never seen what you are saying it has, do you have a picture? How is the pulley retained if the clutch is behind? How is the air gap adjusted? Where is the electo-magnet  and how does it pull? It can't push the internal plate out so must pull something.

 In automotive there are some totally clutchless compressors the have a movable swash plate  and a shear point on the shaft in case it locks up. Supposed to 0 out if it is low on refrigerant, and supposed to shear if the compressor locks.

 Lots has changed since I got out of commercial work, so am open to learning new stuff I haven't (yet) seen.

[Joey Mack]

here is a sample. it is controlled by the EECM. 

[Joey Mack]

I am not able to answer most of your tech. questions, GW..  but what I do know, is it makes trouble shooting A/C issues harder, especially on a road call, and you dont have a laptop with the correct programming.  Even with A-Pads on the truck I have struggled with them.  I dont like to just throw a compressor on as a guess, I want to know why, before I spend the customers money..

[Geoff Weeks]

Ahh, I see I suspect that front cover that is screwed on is a dust cover keeping water and dirt out, and is a conventional clutch below that.  Kind of like the old chafe shield on the Harrison A-6.

 I think I can see a clutch coil behind the pulley.

 If he has one of those, I would pull the cover so I could see what the clutch is doing.

 I haven't run up against one of those yet.

The clutchless are a worse almost throw-a-way compressor.

 I was pondering how it could push instead of pull, now I don't think it has too.

Thank you for the picture.

 I never thought much of the APADS, make it more complicated than it needed to be.

 I had mine set up with Hi and Lo cutoffs, and the low would lock-off until re-set. It would shut the system if 25% of the refrigerant (or there abouts) had leaked, and there was a secondary low pressure that would prevent clutch pull in below about 45 psi on the high side.

 One pound loss on a 4 lb system and you might not even notice it in the cooling unless very hot.

 It would throw some for a loop, but was like the old thermal limiter fuse GM used to use, it could shut down before all pressure is lost, keeping some oil in the compressor.

[Joey Mack]

typically 50 PSI of freon is enough to start the compressor, one of my issues was not being able to jump start or test the compressor with the engine off.  it is a 3 wire harness, unlike the 2 wire harness we know..  wont hurt my feelings if I never learn how to fix this disposable compressor. 

[Geoff Weeks]

Perhaps this will clear it up a bit.