Air Con suddenly goes HOT

[Aussie Q45a]

Wes, I know you have an answer for this prob. However I've searched and can't seem to locate it. Can you remember the heading you posted it under?Thanks

[96Qowner]

Here's the mix door post, if that's the problem:

zerothread?id=156041

[maxnix]

Does it ever cool?

First check charge, then clutch, belt and idlers.

[Aussie Q45a]

Yep Maxnix,So far I've replaced the compressor and belts. The display lights are out on the control unit but were working for a few weeks after I used some Stabalant 22 on the circuit board. I will be pulling it out again and trying the Stabalant 22 again. The A/C will get cold for about 15>20 minutes then blow "HOT" air. Does not matter what buttons I push the Temp stays "HOT". I can change fan speed and direction of air flow (face, foot, windscreen). After the Q sits over night the A/C will operate for 15>20 mins then start blowing "HOT" again.I can remember reading that a member had a similar situation and Wes came up with a process to fix it. Something like, turn ign. on for 10 secs., hold low temp button on for 10 secs., hold high temp in for 10 secs.,. I think the process was aimed at kind of reprogramming the microprocessor in the Amp, or tricking it into thinking it was reading the sensors somehow, diffrently.

I've pulled the glove box and cleaned the sensor beside the blower motor as well as cleaning the sensor in the dash. I was very careful and used a fine art paint brush so as not to damage the sensor.

[maxnix]

That "process" to which you are referring is to place the HVAC into diagnostic mode.

[Q451990]

It sounds like you may be low on refrigerant... it will tend to cause the system to freeze up and stop working - but it's a gradual thing, and will still cool some. Is your problem like flipping a switch (or pressing the ECON button)? Keep in mind that there are (at least) three overides that can tell the ECU to turn the compressor off.

1) The dual pressure switch (located on the drier) can open the circut due to high pressure. Same dual pressure switch can open due to low pressure.

2) Sensor on evaporator coils can tell the unit to open if the coils are freezing.

3) Sensor on compressor can open the circuit due to overheating.

When you have the problem, is the compressor engaged? If not your controller may be crapping out... Mine actually failed in an unusual way that caused the compressor to not run when the display was out. Jerry Tucker said that this was unusual.

Heath

[Aussie Q45a]

That "process" to which you are referring is to place the HVAC into diagnostic mode.

Thanks BrianGuess I'll have to try to fix the illumination display first before I can carry out the self diagostic program. A member posted a repair on the circuit (Pic). Would you happen to know if that was successful? Dumb ? I know but thought someone just might know.

Greg

[Aussie Q45a]

T

It sounds like you may be low on refrigerant... it will tend to cause the system to freeze up and stop working - but it's a gradual thing, and will still cool some. Is your problem like flipping a switch (or pressing the ECON button)? Keep in mind that there are (at least) three overides that can tell the ECU to turn the compressor off.

1) The dual pressure switch (located on the drier) can open the circut due to high pressure. Same dual pressure switch can open due to low pressure.

2) Sensor on evaporator coils can tell the unit to open if the coils are freezing.

3) Sensor on compressor can open the circuit due to overheating.

When you have the problem, is the compressor engaged? If not your controller may be crapping out... Mine actually failed in an unusual way that caused the compressor to not run when the display was out. Jerry Tucker said that this was unusual.

Heath

Thanks HeathI'll check all your suggestion out during the week. I'd hate to think it the controller stuffing up as this has extra buttons for the controller in the arm rest in the back seat and "Air Purerfier" in the parcel shelf.In the pic there are 3 buttons down the right side of the controller.

[maxnix]

That's an option we didn't get, and obvoiously requires more refrigerant and more controls.

Take it to an HVAC professional, not your local garage.

[elwesso]

I agree with Heath... however, next time it does this, turn the AC controller to ECON for 10 mins or so and then turn the AC back on.....

[Q451990]

I always wondered what those extra buttons did when I was browsing yahoo.jp auctions!

Heath

[Aussie Q45a]

It

That's an option we didn't get, and obvoiously requires more refrigerant and more controls.

Take it to an HVAC professional, not your local garage.

It's with a circuit board guru now. He's resoldering sus connections and replacing 7 caps.. He's also replacing bulbs with LED's and resistors. Hopefully after all this I'll be able to get a readout on the display screen and get a code to indicate the reason the A/C starts blowing hot air.

[maxnix]

Cool. Keep us updated.

[Aussie Q45a]

Cool. Keep us updated.

Happy to report a MAJOR win! A/C display is finally ILLUMINATED. The circuit board guru found several "Dry Joints" also 3 of the 7 Capasitors were "wavey" so he replaced them (7) all. While he had the board I got him to replace all the back lights with blue LED's. He roughed up the tops so they wouldn't concentrate light in one spot and put mini resistors on each of them to give them the equivelant of 12 V's. The other win is that it has stopprd blowing hot air, I guess somthing on the board was giving a bad signal (maybe one of the caps.) or maybe it just needed some TLC.Parts $20AUSLabour $150AUS

Piece of mine PricelessAUS

Can't figure how to get at the bulbs in the consul beside the shifter. Wes mentioned 4 bolts that I finally found way down inside the consul but there is no way of getting at them. Any other suggestions?

As always, a huge thanks for everyone's help and input.

[elwesso]

Greg, i'll post in your other thread.

EDIT: I deleted your (accidental) double post.

[Aussie Q45a]

Greg, i'll post in your other thread.

EDIT: I deleted your (accidental) double post.

Thanks Wes,Been trying to post a pic of the Caps that were replaced but I keep getting a bad post message. What am I doing wrong?

Thanks Wes you must have fixed it for me.
Modified by Aussie Q45a at 5:03 PM 5/11/2006

[Aussie Q45a]

LED's without front cover

[elwesso]

is the picture too big? Cant be more than 500k

[Aussie Q45a]

Tha

Greg, i'll post in your other thread.

EDIT: I deleted your (accidental) double post.

Thanks again Wes, I seem to have stuffed this post up. I be pleased if you could sort it out for me. There are plenty more pic' if you would like them.Cheers Greg

[Aussie Q45a]

Must h

is the picture too big? Cant be more than 500k

Must have been holding my tounge wrong!

Maybe if you replace the Capasitors on your A/C it might stop freezing you!!!!!

[Aussie Q45a]

Guess I should take photography lessons. Here is the latest pic of A/C control unit back in place and working fine.

Thanks again to all for your assistance.

CheersGreg