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Unread 05-25-2015, 11:00 AM   #1
alfaitalia
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HVAC issue....NOT blend doors!

Strange one this. My blend doors are working fine...I replaced them already but I took a look to be sure and the both move fine. The issue is that the passenger side will suddenly turn from nice and cold to toasty hot....so I turn it down a degree or two on that side and it gets cold again. A few minutes later it will be hot again...so I turn it down again and it gets cold....for while. You can do this until it gets to "LO" on that side but after a while it goes hot again. It does not do this every drive, in fact it can go for days acting fine then do a week of playing up every day.

So far I have checked the fault codes on the HVAC display....just my usual recirc issue but I've always had that on and off.
I've also reset the HVAC as per the instructions on wjjeeps.com which is basically removing the IOD fuse for a few seconds and then letting the HVAC recalibrate with the ignition on for a few a minute or so. No change. Any ideas folks?
I would particularly like to hear from anyone who may have had the exact same fault and how they cured it. I'm suspicious it might be the infra red sensor that monitors that side of the car but am not sure and nor do I know how to test it. The FSM is not much help, pretty much just saying that if its broken replace it!

As always I look forward to your replies. Cheers.

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Unread 05-25-2015, 11:11 AM   #2
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I have the same problem but with heat not the A/C. I try to Ignore It.
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Unread 05-25-2015, 11:50 AM   #3
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Doing a bit of research whilst I'm waiting for all your answers(!). Looks like others folks with the same problem on the mighty google have cured the issue by having these refrigerant recharged. Apparently when the refrigerant gets low the control cuts cold air supply to the passenger side first (at least when in AUTO. I can find nothing in the FSM to back this up but it seems to cure the issue in some cases. I used to get my AC changed every two years but its not been done for three now so might be the way forward.
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Unread 05-25-2015, 12:52 PM   #4
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Mine does that with heat In the winter. I believe the blendoors randomly open and close by themselves, just a computer glitch I'm guessing.
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Unread 05-25-2015, 09:25 PM   #5
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Originally Posted by alfaitalia View Post
Doing a bit of research whilst I'm waiting for all your answers(!). Looks like others folks with the same problem on the mighty google have cured the issue by having these refrigerant recharged. Apparently when the refrigerant gets low the control cuts cold air supply to the passenger side first (at least when in AUTO. I can find nothing in the FSM to back this up but it seems to cure the issue in some cases. I used to get my AC changed every two years but its not been done for three now so might be the way forward.
I was gonna suggest that the IR sensor is faulty or dirty.I never heard of a system cutting cooling to one side of a vehicle when the refrigerant is low.If the refrigerant is low its not gonna cool either side correctly so cutting one side off isnt gonna boost the other side.If the system is lets say half full of R134A,the air coming out of the vents is say 50 degrees.Shutting off the passenger side isnt gonna raise the temps on the driver side,because the system is still half full and can only make 50 degrees.Its an interesting theory but if the temp on the driver side is cold,and the air is cold on the passenger side when working,my money says the refrigerant is fine.Why do you change the ferfrigerant every 2 yrs?
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Unread 05-25-2015, 09:28 PM   #6
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I was gonna suggest that the IR sensor is faulty or dirty.I never heard of a system cutting cooling to one side of a vehicle when the refrigerant is low.If the refrigerant is low its not gonna cool either side correctly so cutting one side off isnt gonna boost the other side.If the system is lets say half full of R134A,the air coming out of the vents is say 50 degrees.Shutting off the passenger side isnt gonna raise the temps on the driver side,because the system is still half full and can only make 50 degrees.Its an interesting theory but if the temp on the driver side is cold,and the air is cold on the passenger side when working,my money says the refrigerant is fine.Why do you change the ferfrigerant every 2 yrs?
I agree on all points. Esp having to recharge/replace refrigerant every few years. Sealed system with virtually no maintenance needed. If its loosing refrigerant you have a leak.
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Unread 05-26-2015, 12:30 AM   #7
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I've argued this point before and very few people agreed so won't push the point but I've always changed my refrigerant every two to three years in all my car's. The fluid slowly loses its efficiency over time and the sysyem becomes less cold. I back this up two ways. Firstly the place I go to get it changed guarantees it to be 10% colder if you have not had it changed on the last 24 months and it always is (or more). And secondly several cars I've had have had a 24 month refridgerant change in the handbook as part of the service schedule and they must do it for a reason. Also this means the system is pressure and vacuum checked for leaks and I know the correct amount of oil is in the system. My Jeep is nearly 12 years old and 125,000miles.....the AC has never failed and every part is original and never leaked......how many of you can say the same? You would not leave the oil that lubes your crank bearings for over two years so why lube your compressor bearings and seals with old oil that's been heated and cooled hundreds (thousand?) of times.....just my view of course. It's cheap to do and only takes an hour so why not. Before you say, I'm not losing fluid as I get a printout of how much they extract and how much was needed to refill and it's always within fractions of an ounce of each other. Will get it done soon to see. As said I doubt it will fix the issue I started this thread about as I've never had this issue before but it seems to have for others so who knows!

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Unread 05-26-2015, 12:34 AM   #8
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I was gonna suggest that the IR sensor is faulty or dirty.I never heard of a system cutting cooling to one side of a vehicle when the refrigerant is low.If the refrigerant is low its not gonna cool either side correctly so cutting one side off isnt gonna boost the other side.If the system is lets say half full of R134A,the air coming out of the vents is say 50 degrees.Shutting off the passenger side isnt gonna raise the temps on the driver side,because the system is still half full and can only make 50 degrees.Its an interesting theory but if the temp on the driver side is cold,and the air is cold on the passenger side when working,my money says the refrigerant is fine.Why do you change the ferfrigerant every 2 yrs?
How do you test the IR sensor? It does not/cannot cut cooling to one side, as it's all one circuit. What people are saying is that the computer moves the passenger flap to stop /reduce cold air on the passenger side. Unlikely as far as I can tell but lots of folk on the net have had the same issue cured by a recharge so what have I got to lose by trying?

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Unread 05-26-2015, 07:16 AM   #9
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Originally Posted by alfaitalia View Post
I've argued this point before and very few people agreed so won't push the point but I've always changed my refrigerant every two to three years in all my car's. The fluid slowly loses its efficiency over time and the sysyem becomes less cold. I back this up two ways. Firstly the place I go to get it changed guarantees it to be 10% colder if you have not had it changed on the last 24 months and it always is (or more). And secondly several cars I've had have had a 24 month refridgerant change in the handbook as part of the service schedule and they must do it for a reason. Also this means the system is pressure and vacuum checked for leaks and I know the correct amount of oil is in the system. My Jeep is nearly 12 years old and 125,000miles.....the AC has never failed and every part is original and never leaked......how many of you can say the same? You would not leave the oil that lubes your crank bearings for over two years so why lube your compressor bearings and seals with old oil that's been heated and cooled hundreds (thousand?) of times.....just my view of course. It's cheap to do and only takes an hour so why not. Before you say, I'm not losing fluid as I get a printout of how much they extract and how much was needed to refill and it's always within fractions of an ounce of each other. Will get it done soon to see. As said I doubt it will fix the issue I started this thread about as I've never had this issue before but it seems to have for others so who knows!

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Well I can say the 89 Chevy truck my grandfather bought new had over 500,000 miles with an untouched a/c system. Would still blow 38* from the center vents. And refrigerant is a gas, not a fluid. In fact, the refrigerant recovery machine reuses the refrigerant and puts it back in the a/c. And the oil doesn't get contaminated as it would in the engine as again, its a sealed system. And think about this, do you ever change the refrigerant in your fridge or freezer? Is it as cold as it was 10 years ago?

But whatever works for you.

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Unread 05-26-2015, 11:51 AM   #10
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This is why I did not want to get into this (off topic) debate. A fridge? Hardly comparable. Do you bounce your fridge all over the road and off road?...do you not use it for weeks at a time them expect it to work fine? Do you use your fridge in extremes of hot and cold? Thought not! Different type of compressor too. Older (pre ozone friendlier...probably like the car you mention) ac systems used to stay colder for longer....it's the newer stuff that's recommended to have a 24 month change. Each to there own.

Now BOT! I think my problem could be a control panel issue rather that IR sensor. I ALWAYS leave it on Auto on the right hand knob. But I've noticed today that if I put it in one of the other positions the passenger side stays cold. I don't know of that helps anyone with a suggestion of a fix.

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Unread 05-26-2015, 12:42 PM   #11
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Had this happen to me two summers ago in hot as hell Texas, passenger side went full hot, i pulled over and put the key on/off at least ten times to try and get it to reset the system. It did it 3 different times and it always eventually corrected itself. As to why it happened, I can only conclude a fault in the AZC head unit. It has not happened in over a year so next time it happens I am going to consider spending the 400 for the new unit.
BTW replaced blend doors/recirc with heater treater all metal doors five years ago. Along with passenger and recirc door actuators.
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Unread Yesterday, 12:01 AM   #12
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Quote:
Originally Posted by alfaitalia View Post
How do you test the IR sensor? It does not/cannot cut cooling to one side, as it's all one circuit. What people are saying is that the computer moves the passenger flap to stop /reduce cold air on the passenger side. Unlikely as far as I can tell but lots of folk on the net have had the same issue cured by a recharge so what have I got to lose by trying?

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If you do the AZC self diagnostic mode system test,(it will show input faults,ie:IR thermistor circuit open,IR thermister circuit shorted,etc.That might help being its related to your issue.
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Unread Yesterday, 01:48 AM   #13
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No faults except recirc door...which I've always had. Very strange.

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Unread Yesterday, 12:44 PM   #14
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Forget what I said about it not getting warm on passenger side in anything other than AUTO.....it was in manual all today and was getting hot on the passenger side by the end of the day. Darn it...thought I was onto something there. Back to the drawing board.

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Unread Today, 05:19 PM   #15
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Right....after much experimentation I'm 99 percent certain I've narrowed the poblem down to the IR sensor in the control panel. If I put my finger over it the passenger side becomes as cold as the drivers side almost instantly. When I remove it, it becomes warm on the passenger side....not always straight away but sooner or later. This is a bit of a bugger as the sensor is not available separately...it's part of the control panel (according to wjjeeps at least and judging by the tons of other "facts" that are wrong on that site I'd better check that is correct!). That site also warns that dash cleaners, vinyl dressing etc can damage the sensor and I can't say I've never used those cleaning products ! Think my first step well be to clean the lens with something.....I was thinking of the sort of liquid used to clean the laser lens on CD players. Worth a go ands I've nothing to lose...and I happen to have some. Will report back if it offers any improvement...just in case any of you ever get the same issue. Anyway it's quarter past midnight here....off to bed!

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