Thread: Aircon help needed

Switches on then switches off...... sounds like normal cycling to me however if the fan is losing power then it's likely a bad earth or poor power connection in the fuses, fan switch or relay. At a guess check your fan relay, power to it and fan itself, as most A/C systems are wired so that they only work when the fan is on. So if the fan fails, the a/c system switches off.

Won't be TX valve and won't be compressor. Running compressor by applying direct power won't achieve anything, won't hurt for a few seconds if it is however the problem lies where I sugguest above.

Thinking about it a little more, I wonder if someone wired the cabin fan to the same wiring of the condensor fans ??? 8O

Hellspawn.
I may have 2 seperate problems.
1.When I press the A/c button on, it lights
2. By sliding the fan speed on the blower works.
3. The cooling fans on the radiator start and the clutch engages.
I realize that A/C has a normal cycle to turn on and off automatically to allow temp flow.
The cut out of all power to to the Fan and A/c switch could be a seperate fault. It only occurs very occassionally and all I do is flick the fan speed switch off and on again and it works.

When I loose the cold air, Cabin fan is still blowing, but I get no cold air. Also the Clutch is disengaged.
( When I connected power direct to the compressor cold air was again coming into the cabin)
So I must have by passed something in the electrical system. Ie the dual pressure switch.

I will pull the fan relay and try another relay and see how it goes.

Still reckon it's a crook connection for the "drop out" problem.

Second problem if the A/C button is still illuminated when there is no cold air then the temp sender is suspect, wires to it etc. as that's the next point of control. If the A/C light is out then it's back to the fuse box of further if there's no power there either on the fuse. If you have self resetting fuses you might find a wire earthing out causing the fuse to go open circuit. You sure the drain hole for the condensor is clear ? Maybe it is the "ice up" sensor because the thing is full of water...

I can't help anymore than to say this, it's a simple system of 12V on or off switches. Start at a known point (like the fuse box) and keep working down the wires using your meter until the power stops. Then bridge over that component, like I say it's on or off so bridging makes it on and see if that makes the symptoms worse or better testing EVERYTIME you change something.

You're going to need patience to nut it out but at least you'll know for next time...... unless it gets too much and you take it to someone.

Originally posted by Rovernaut

1.When I press the A/c button on, it lights

On my disco i can press the air con button, and as hellspawn says it doesnt actually work until the fan is turned on. As a result as soon as i turn the fan on the light in the air con button comes on.
I had the same thought as hellspawn suggested, possibly an earth or a short somewhere. Are you blowing fuses at all? Mind you my knowledge of auto electrics is limited, i do understand the very basics. Matt

Thanks Ace and Hellspawn for you input.
this is the latest
I removed the drivers side kick panel and located the A/C logic relay and the Compressor Clutch relay. ( I have a Rave CD , so it show pictures of each component location, other wise it is hit and miss.)

I pulled both those relays and replaced them with working ones I had as spare. I turned the A/c on and it gave a blast of cold air. I thought good, then I went for a half hour drive and the A/c seemed to work fine with only the normal on /off operation of the compreesor as a working A/c unit does. I got very cold air and durng this time hadn't experienced the fault lkie I had before. ( normally I would have had warm air circulating by then).
So fingers crossed it was infact a relay loosing it's contact only.
I will not know until I drive a bit more and over a longer period.

Just for interest, this is how the Rave manual describes the A/C circuit operation.

CIRCUIT OPERATION
Compressor Control (MFI–V8)
With the Ignition Switch (X134) in position II, battery
voltage is applied to the Ignition Load Relay (K127).
The relay is energised, applying battery voltage to
the Compressor Clutch Relay (K108) and the A/C
Logic Relay (K170). When the Front Fan Speed
Switch (X247) is turned to positions I, II, III, or IV
and the Front A/C Switch (X225) is turned on,
ground is provided to terminal 86 of the A/C Logic
Relay (K170) through the closed contacts of the A/C
Dual Pressure Switch (X102) and the Front A/C
Evaporator Temperature Switch (X101).
The relay is energised, applying battery voltage to
the Engine Control Module (ECM) (Z132), which
signals the ECM that compressor operation has
been requested. The ECM then provides ground to
the coil of the Compressor Clutch Relay (K108). The
relay is energised, applying battery voltage to the
Compressor Clutch (K107). Compressor Clutch
operation is now controlled by the status of the A/C
Dual Pressure Switch (X102) and the Front A/C
Evaporator Temperature Switch (X101).
The Front A/C Evaporator Temperature Switch
(X101) is fitted in the airflow out of the front
evaporator to sense the temperaure of the exterior
fins. Should ice begin to form due to low
temperature, the switch will open. The A/C Dual
Pressure Switch (X102) monitors refrigerant
pressure in the high pressure line. Should pressure
become too high or too low, the switch will open.
When one or both of these switches open, the
ground supply to terminal 86 of the A/C Logic Relay
(K170) will be interrupted. The relay de–energises,
removing battery voltage from the Engine Control
Module (ECM) (Z132), which signals the ECM that
compressor operation should be turned off. The
ECM removes the ground supply to the coil of the
Compressor Clutch Relay (K108). The relay then
de–energises, removing battery voltage from the
Compressor Clutch (K107), thereby disengaging the
Compressor.

I'm glad its sorted (touch wood), let us know how it goes. Matt

Drove around most of the day with A/con switched on. It worked!!!!!!.
Now the wife is happy as the heat was getting to her on prevoius trips making it uncomfortable.

It was the relay.

It only took me 2 years to find it!!!!.

I was not keen in giving my baby to a mechanic to part my wallet with big $$$$$. [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img] [img]style_emoticons/<#EMO_DIR#>/biggrin.gif[/img]

g'day Rovernaut

its all part of being on this site
these guy's around will do all they can to help out
thats what makes this site great [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img] [img]style_emoticons/<#EMO_DIR#>/laugh.gif[/img]