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Wayne
Wayne, Journeyman
Category: Heavy Equipment
Satisfied Customers: 9633
Experience:  34 years experiance as engine rebuild and problems.Thermo-King repair and trouble shooting.
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Working on a 1996 379 peterbilt w/3406e cat A/C..vent..gauges..coils

Customer Question

Working on a 1996 379 peterbilt w/3406E cat A/C in cab @ vent blows 60 In sleeper it blows 50, gauges read 35 and 250. Have cleaned coils in cab and sleeper, what else can be checked?
Submitted: 7 years ago.
Category: Heavy Equipment
Expert:  Wayne replied 7 years ago.
Chat Conversation Started
wayne :

HI I'm Wayne,

wayne :

I will try to help you with this,

wayne :

seen your question earlier,but did not respond, thinking about it

wayne :

what I have to say is vent in cab, with thermometer is 60, and sleeper is 50, the coil for sleeper is closer, and the vent for cab is getting engine heat , plus a minor coolant temp, all this being said, your pressure of 35 lbs, low side (suction) , is a little low, should be around 45 to 60 lbs, depending on ambient Temp. head pressure is good, so I would say you are a low a bit freon ,I would add about 1/2 to 3/4 of a lb.

Customer:

Ok, we had already tried that, now we went ahead and replaced compressor, dryer, orfice and flushed complete system, still not getting but 60 in cab and sleeper. Out side temp is 98.

wayne :

Hi pkdwbprs,

wayne :

Is your compressor shutting off, when this is happening ??

wayne :

Did you clean and wash the condenser, you said coils in cab, what about the condenser

wayne :

Let me know

Customer:

No compressor does not shut off, yes cleaned condenser

wayne :

Well this getting a little weird, what about the expansion valve. and your sure the compressor is not short cycling, on-off.

wayne :

the feeler bulb of expansion valve has good contact

Customer:

has orfice tube @ cab and expansion valve @ sleeper, changed both! will double check but it doesn't seem to be cycling on -off.

Customer:

If we were not getting a good vacuum before recharging it would show on gauges correct? after changing everything high is still 250-260 low is 40

wayne :

when recharge, as I tell all my customers, evacuate to 28" for 2-3 hours , you will see smoke from , pump, but that's good, that is moisture boiling out coming out of system, If you can not pull a 28" vacuum, you have a leak