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eddo
Advanced Member
USA
311 Posts |
 Posted - 03/28/2016 : 3:57:48 PM
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Hello all,
I've got a stumper here.
I'm working on a stock International DT466E, in a 1998 4700 Chassis, with a York Style compressor. The a/c unit in the cab is a Red Dot unit.
Last summer, I had an a/c compressor give out. I replaced the compressor with new, flushed the system, put on a new clutch/coil, and replaced the receiver drier. Charged it back up, and all looked good.
I went on vacation, and it gave out while i was gone. It was taken to a WWWilliams shop, and they said a drier o-ring was bad, and replaced it. It didn't work the next day.
I got back from vacation, and replaced the expansion valve. (both gauges were reading low.)
It worked great for a couple of weeks, then no more cooling. Again, gauges were both reading low, so I replaced the expansion valve.
Then the odd stuff started.
It worked great for a few weeks, then one day it started blowing warm. I pulled the truck the next day, and found the pressure readings to be within specs. I sent it on a short route, and that crew loved how cool the a/c was. I put the truck back on the long route, and it worked great for a couple weeks. Then it started this mess all over.
Since then, I have not been able to make it fail with the gauges hooked up. The crew complains about it, and when I check it the next day- it all checks good. I have replaced all the moving parts twice since last summer- trying to fix this issue without being able to replicate it. I have checked and chased wires. I have blown out the condenser, and evaporator. I have replaced the thermostat. I added a secondary heater control valve to stop hot water from getting to the unit. I have disconnected and bypassed all pressure switches.
Last week, it stopped blowing cool on Monday. I waited for them to come in, and saw and felt for myself that it was not blowing cool.
The a/c clutch was engaged, no bubbles in the sight glass, heater valves were all closed.
I checked the a/c unit thermostat- it worked.
I checked the power switch. It worked. The coil had good power.
The a/c belt was tight.
It all looked good, but was not cooling. The driver shut the engine off, unloaded his cargo, and drove it 50 feet to my shop and where my gauges are.
By this time it was blowing ice cold and pressures looked great...
The next day I replaced about everything: Compressor, clutch/coil, drier, exp valve, flushed the entire system twice, a/c idler pulley assembly, and re-blew out the condenser. Sent it on route for 3 days and all was great.
Til Saturday, it worked for an hour, then no more cooling.
Today, with me doing nothing- it's working great.
Any advice?????? I'm going more bald than ever on this one... |
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ed587
New Member
2 Posts |
Posted - 03/29/2016 : 03:49:36 AM
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| condenser fans. just a thought |
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eddo
Advanced Member
USA
311 Posts |
Posted - 03/29/2016 : 08:49:17 AM
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condenser fan is working properly. :/
#StumpedInAZ
:) |
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slippert
Top Member
USA
630 Posts |
Posted - 03/29/2016 : 09:02:31 AM
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| I had A/C on semis that would do kind of the same if over charged.... Freeze up...work for awhile, then not cool, then start working again... of course always seem to be working good in shop when setting still.... I always left some bubbles in system, if I charged them in early spring when temps here were lower... because if they were fully charged in colder temps, when it got hot summer they would freeze and seem to be to full with freon expansion....Not sure how much ambient temp variation you get in AZ from morning to mid day to evening or even day to day this time of year? anyway sounds like system is freezing or not able to flow to me... looks like you covered most everything else! good luck |
Edited by - slippert on 03/29/2016 09:16:05 AM |
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eddo
Advanced Member
USA
311 Posts |
Posted - 03/29/2016 : 09:46:06 AM
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That was one of my thoughts as well. I have had evaporators freeze up, but that usually results in low air flow.
I, too, leave just a few bubbles in the system this time of year. Then it should be absolutely perfect when the outside temps are over 100.
could something else be freezing up? blocking flow internally?
One of my earlier thoughts was just bad expansion valves. I have had those stick, then work ok, then stick again (either open or closed.) to combat this idea, I changed expansion valve manufacturers... But still occasional issues. |
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slippert
Top Member
USA
630 Posts |
Posted - 03/30/2016 : 04:39:10 AM
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With the way things are manufactured these days and the majority of them coming from overseas, I wouldn't be surprised to have a bad/new part... I know when I worked for the trucking company as the trucks aged, and a/c gave us more issues we basically refurbished system new hard parts and all hoses.... After that system would normally run trouble free for a few years..Sounds like you have pretty much done that already, and sounds like system has been flushed out a few times so shouldn't be an issue of too much oil either...
Not sure what you had done hose wise on that unit, but wonder if it could have a flap in one of the rubber lines that is blocking flow part time? Seems like if it was a hose, a frosty area would be visible some where? Seems like we use to have more issues with the aluminum compressors, vs the cast ones... can't remember if the yorks were aluminum and the tecumsehs were cast or could get both either way? Sounds like you have already replaced comp at some point, but might be worth trying different one maybe a suction/ discharge valve issue inside comp?
I take it this truck is just a single system? and has no sleeper/rear unit after the one in the cab? been awile but the Kenworths I use to work on had both and seems like it flowed through front A/C then had to flow through a second unit in rear |
Edited by - slippert on 03/30/2016 06:06:06 AM |
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eddo
Advanced Member
USA
311 Posts |
Posted - 05/24/2016 : 3:46:42 PM
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UPDATE:
After replacing just about everything again- expansion valve, drier, thermostat, and adding the evaporator to the list of things replaced (thought perhaps something was stuck inside of it- causing a blockage and thus low side low pressure,) I buckled down and replaced the condenser too.
This did nothing to help.
the only thing left to replace was the hoses, which I had blown through with compressed air, and by mouth, and had all seemed good.
So I replaced the hoses too.
3 weeks later and it is still working perfect. Something had to be in one of the hoses going to or from the evaporator- that was only an issue sometimes (my guess is it was the hose heading to the evaporator after the drier.) I've never seen anything like that before.
I'm calling this one fixed. :) |
Edited by - eddo on 05/24/2016 3:47:49 PM |
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RonF
Top Member
867 Posts |
Posted - 05/25/2016 : 03:51:08 AM
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| It is possible that one of the hoses were collapsing inside. |
US Army retired CMBT |
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eddo
Advanced Member
USA
311 Posts |
Posted - 05/31/2016 : 10:49:02 AM
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| that's my guess, RonF. |
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jeeptjken
Senior Member
147 Posts |
Posted - 05/31/2016 : 11:08:45 AM
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did you change the inline filter ?
it will be inside one of the hard lines under a conector |
How did you get the gosinta in the whatchamacallit |
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eddo
Advanced Member
USA
311 Posts |
Posted - 05/31/2016 : 1:37:07 PM
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| the only filter my system has in the receiver/drier, and it got changed a few times, lol |
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jeeptjken
Senior Member
147 Posts |
Posted - 06/01/2016 : 03:47:15 AM
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| there should also be a small filter inside one of the ridged tubes you can only remove it by disconnecting the fittings and pulling it out with needle nose pliers |
How did you get the gosinta in the whatchamacallit |
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slippert
Top Member
USA
630 Posts |
Posted - 06/01/2016 : 06:55:35 AM
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quote:
Originally posted by jeeptjken
there should also be a small filter inside one of the ridged tubes you can only remove it by disconnecting the fittings and pulling it out with needle nose pliers
What your describing sounds like an oriface tube setup...? if system has an expansion valve ...shouldn't have an oriface tube as far as I know... one or the other was the normal back a few years when I worked on them daily... GM always ued oriface tubes in their systems, don't remember an other filter than the reciever/dryer myself... |
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A/C issues- 1998 IC 4700
