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the A/C in my car had been broke since I bought it, I replaced the evaporative coil, heater core, dryer, along with the orifice and return line... essentially I replaced everything but the compressor and the condensor.... My question is that on a hot day my A/C won't get any cooler than 75*, is this because I have a clogg somewhere in the system, or am I low on freon. The A/C compressor will cycle on and off if it is low, Right? It doesn't cycle on and off or anything and I am at my wits end... I spent almost $600 on my A/C and that was even with getting the parts 15% cheaper by going through a friend. Any ideas???
 

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MYLITTLEHO said:
is this because I have a clogg somewhere in the system, or am I low on freon. The A/C compressor will cycle on and off if it is low, Right? It doesn't cycle on and off or anything and I am at my wits end...
Talking R12, right?

Put a set of gauges on it. It can't be clogged because you mention it is not cycling. Also, it can't be low or (again) it would be cycling. You can only troubleshoot this with a set of gauges.

FWIW, my guess is that you are overcharged.
 

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I'm with Puter, overcharged will do what you've described.
If it's R134 it should still cycle occaisionally, but 134 will not cool nearly as well on a stock cooling system.
Does it do any better cruising than idling? A weak fan clutch can cause that.
 

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4play said:
Does it do any better cruising than idling? A weak fan clutch can cause that.
That's what mine does! Is there anything else that could cause this? I haven't noticed any cycling of the compressor, so I don't think it's low on refrigerant . . . but I don't have guages . . .
 

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If your A/C is blowing warmer at idle, it could be a lack of airflow across the condenser as mentioned above, and/or it could also be that when you are idling, the compressor is turning slower, which will cause your vent temperature to be warmer than when cruising, especially if you have pulleys, because the compressor will be turning even slower.

Overcharging can cause the entire system to run at a higher pressure than usual. This would cause a warmer vent temperature at all times, of course being worse at idle. The best way IS to diagnose your A/C system problems with a set of gauges. This will help you see if you are overcharged, undercharged, have a glog, have a weak compressor, etc.

The low pressure switch will turn the compressor off when pressures on the low side drop below the desired/set pressure, and back on when the pressures are acceptable. When holding the motor at 1500-2000 rpm's, it's not uncommon to have the compressor cycle on and off. This prevents the evaporator from turning into a block of ice from the pressure/temperature dropping so low and freezing the evaporator, which would block airflow through the evaporator, and thus through the vents. My A/C is about 55-60 degrees on a hot day, and 35-40 at night. It has gone as low as 20 degrees on a cool day while raining. I accomplish this by bypassing the low pressure switch to prevent the compressor from cycling on and off. I would not recommend this though, because I don't know if it could harm anything, but mine has been fine so far.

Frank
 

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aew93 said:
Check your hi/low switch......right behind the passenger side strut tower round thing with all the vacuum lines. I think that is what that piece is called not 100% though.

Tony
It's called a pressure switch. I bought an f350 and 2 days after I bought it the ac quit. All I had to do was change the pressure switch.

Does your compressor engage at all? If it does NOT, then test your pressure switch by:
1) unplugging the two wires that go to it
2) Use a jumper wire to connect the 2 wires you just unplugged.
3) Start the car and turn on the a/c (dont do this for a long period of time, just enough to see if your compressor turns on and if it will blow cold air).
4) Look to see if your compressor is now working and see if your a/c is blowing cold air.


If the compressor comes on with these 2 wires jumped together, then it is either a bad pressure switch, or your freon charge is too low. If it blows cold air with the wires jumped, then it is probably just a bad pressure switch. If the compressor comes on with the wires jumped, but does NOT blow cold air, then you probably have low freon pressure. The reason for the pressure switch is....becuase if you have low freon and the compressor comes on, it will burn up the compressor.

Hope that helps.
 
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