2017 cat 420 backhoe with 1700 hrs.my air conditioner doesnt want to cool in the higher rpms but is ice cold below 1600 rpm.new filters,clean condenser and our mechanic says the pressures are where they need to be.also brand new belt and its tight .I am not an A-C man so any suggestions/experience with this kind of problem?
- Thread starter rrman61
- Start date
Geo-TH,In
Well-known Member
Air conditioners work on a pressure difference between the high side and the low side.
What are your pressures at 1600 and max rpms?
You will have to figure out how to make the pressure you measured at 1600 the same at higher rpms. You may have too much freon. Only a guess without knowing the pressures.
I have no clue if you have a fixed orifice or expansion valve.
Good luck.
Is your condenser clean?
What are your pressures at 1600 and max rpms?
You will have to figure out how to make the pressure you measured at 1600 the same at higher rpms. You may have too much freon. Only a guess without knowing the pressures.
I have no clue if you have a fixed orifice or expansion valve.
Good luck.
Is your condenser clean?
jimg.allentown
Well-known Member
Possibilities:
1) Clutch slipping. Maybe not holding at higher RPMs?
2) Heater not being closed off at higher RPMs? Is it vacuum operated? Is there a valve in the heater hose that is supposed to shut off coolant flow through the heater core?
3) Low vacuum at higher RPM causing blend door to move to the heat side at higher RPMS?
4) Overcharged system. Possibly too much refrigerant in the system. At higher RPMs, high side pressure could be hitting the high pressure cutout switch.
Those are my ideas of what I would check first.
It would be a big help to see gauge readings at around 1800 to 2000 RPM.
1) Clutch slipping. Maybe not holding at higher RPMs?
2) Heater not being closed off at higher RPMs? Is it vacuum operated? Is there a valve in the heater hose that is supposed to shut off coolant flow through the heater core?
3) Low vacuum at higher RPM causing blend door to move to the heat side at higher RPMS?
4) Overcharged system. Possibly too much refrigerant in the system. At higher RPMs, high side pressure could be hitting the high pressure cutout switch.
Those are my ideas of what I would check first.
It would be a big help to see gauge readings at around 1800 to 2000 RPM.
MARK ROBKE
Well-known Member
I am thinking low suction pressure at high rpm-maybe due to low charge (was it weighed in the correct amount?)-restriction at expansion valve/orifice tube-or evaporator covered with dirt causing poor air flow across it (would cause high suction pressure, I think). Pressures can look good at idle and low rpm but in reality they should be checked at operating rpm. Mark.
caterpillar guy
Well-known Member
When did he look at it and what time of yeear or temperature outside. IF cool to cold it probably has to much refrigerant in it. The best day to charge one is the hottest day of the year.
RogerinIowa
Member
You cleaned condensor. How about evaporater? Drain lines open?
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