mark

Does anyone know the possible causes for my a/c compressor cutting
off? It runs about 50% of the time and is new. What gives signals to
the a/c relay to open? There is no pattern as to speed, or how long
it's been running. It also has a new relay, evaporator coil and dryer.
Please help.

E. Meyer

On 7/10/04 5:02 PM, in article
c390c9fd.0407101402.14048003@posting.google.com, "mark"
<mjim@volcanomail.com> wrote:

> Does anyone know the possible causes for my a/c compressor cutting
> off? It runs about 50% of the time and is new. What gives signals to
> the a/c relay to open? There is no pattern as to speed, or how long
> it's been running. It also has a new relay, evaporator coil and dryer.
> Please help.

If you have the temperature bar all the way cold and the fan on max and it
cycles, it means the Freon charge is either too little or too much - it will
cycle in either case.

Randolph

mark wrote:
>
> Does anyone know the possible causes for my a/c compressor cutting
> off? It runs about 50% of the time and is new. What gives signals to
> the a/c relay to open? There is no pattern as to speed, or how long
> it's been running. It also has a new relay, evaporator coil and dryer.
> Please help.

When the outside temperature is only moderately hot, it is normal for
the A/C to cycle on and off. Does the system keep the car cool?

There are two relays in the A/C system. One switches battery voltage to
the A/C compressor clutch, the other switches batter voltage to the A/C
condenser fan.

The relay coil for A/C condenser fan gets battery voltage from the
ignition switch and gets ground through the series connection of the
thermostat mounted on the evaporator, the A/C on/off switch and finally
the cam on the ventilation fan that is on whenever the ventilation fan
is on (any speed but off).

The relay coil for the A/C compressor clutch gets battery voltage from
the ignition switch and is grounded by the ECU. The ECU gets the A/C
request through a series connection of the A/C high pressure switch, the
thermostat mounted on the evaporator, the A/C on/off switch and finally
the cam on the ventilation fan that is on whenever the ventilation fan
is on (any speed but off).

When the ECU gets an A/C request, it will bump up the idle speed a bit,
enrich the idle mixture a tad and then turn on the compressor. For
trouble shooting purposes, the trip through the ECU is only a small
delay.

Check under the hood if the condenser fan and A/C compressor both cycle
on and off at the same time. If the fan keeps running after the
compressor has stopped, it usually means that the over-pressure switch
has been tripped (e.g. due to too much refrigerant in the system).

If the fan and clutch cycle at the same time, it is either the normal
cycling of the system, or it could be that the system is low on
refrigerant.