a/c blows warm at idle

rispoli_23 · Jul 28, 2011

hi guys, ok on my last thread i was having an issue with my car surging while the a/c was on even if i was driving it would jerk and suge while going down the road but it blew cold at idle and while driving anyway yesterday i recharged it with a small can of r134a and was excited because the surging and jerking stopped while driving and it blows cold but then today i noticed that now it blows cold while driving and warm at idle ughhh any suggestions

thanks in advance

wmburns · Jul 28, 2011

Is the radiator and AC coil clean on the inside and out?

Are all of the air dams and fan shrouds in place?

Does the cooling fan run (on BOTH speeds for the GT)?

Is the AC short cycling?

Inspect the AC clutch. Look for oil contamination or evidence that the clutch is slipping or over heating. Check for excessive play on the AC clutch pressure plate.

How did you MEASURE the Freon charge? Problem is this could be low on Freon or over charged. Would be handy to know the high and low pressure readings at idle, 1k, and 2k.

Review the following threads:

engine trouble with AC on - Ford Mustang Forums

1999 mustang ac questions?? please help - Ford Mustang Forums

rispoli_23 · Jul 28, 2011

the fan is on while the a/c is on and there is nothing blocking anything, its weird because before i added freon it worked fine at idle except is was cycleing on and of more then i think but the car was surging bad while driveing so a tech at my work said to add a lil freon thats its prob to low, i did not hook a gauge up to it, yes i know stupid, so now it works fine while driving and no surging but the clutch is not engaging at idle

wmburns · Jul 28, 2011

Confirm there are no DTC codes. Some DTC codes will disable the AC.

Confirm there is +12 volts to the low pressure swich VT wire. Next test for +12 volts from the low pressure switch DB/YE wire.

If voltage this means there is a "issue" somewhere down stream. Perhaps in the high pressure switch. Additional testing will be needed.

If no voltage, confirm that jumping the low pressure swich causes the AC compressor to engage.

If the AC clutch engages when the low pressure switch is jumped and since your AC works at road speeds, to me this means the system is low on Freon.

Note, I'm doubtful about the symptoms as they have been reported. My doubt centers around the report that the clutch is not engaging at all at idle. That just doesn't make sense. If true, it shouldn't work at all.

rispoli_23 · Jul 28, 2011

thats exactly what i thought but it is true it was ice cold on the highway on the way to work this morning and when i exited off and came to a stop it got warm then cold when i drove again so when i got to work i shut it off and popped the hood turned it back on turned the ac on high and watched the compressor it never once came on so i shut it off to see if i can turn the clutch by hand and i did so its not locked up i guess .. turned the car back on with ac on max still nothing, i guess ill see what happens when i drive home

thank you so much for taking the time to help me

rispoli_23 · Jul 28, 2011

how do u jump the switch

wmburns · Jul 28, 2011

Usually one applies a temporary jumper to a switch with a scrap piece of wire placed across the switch terminals.

rispoli_23 · Jul 28, 2011

on the switch itself or the harness that plugs into it .. sorry

wmburns · Jul 28, 2011

The jumper is to provide a path for the electricity to flow around the switch. Is there any electricty in a switch with no wires attached?

It makes no difference to the electricity if the jumper is installed by back feeding the wires at the connector or by removing the connector and jumping from the connector face. The decision has to made by you based upon which method you think is easiest.

OK.....prob easiest to disconnect the electrical connector and jump the contacts from the connector face.

Note, that if testing for voltage coming out of a switch, the switch has to be "in the circuit" for the test to have meaning.

This is the tech section. If you have to have pictures to jump a switch or test for the presense of +12 volts on certain wires, then perhaps you should consider the services of a professional. Working on AC systems can be hazardous. Some tasks if done incorrectly could result in personal injury.

rispoli_23 · Jul 29, 2011

thank you i am going to try and work on it tonight

Jinx · Jul 18, 2016

Back from the dead, but this is happening with mine now. Was there ever a solution???

a/c blows warm at idle

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