Auto Air Con only works on Lo. Help!

[Root Ginger]

Well I'm at a loss with this one.

I was driving along yesterday and suddenly noticed the cabin getting really hot. I felt the vents and they were blowing out hot air. After a bit of fiddling I got cold air to come out but, only when on Lo. I did a software reset but, this doesn't seem to reset the Auto Air Con unit, as the settings were exactly where I had them before.

Does anyone else have experience of this or any ideas? I tried a search but can't use Lo as it's too small

[miniredcooper]

No cold air apart from on low - with this tropical heatwave we're having in the uk that must be hard

Anyway - sounds like a strange one - I could understand if no cold air whatsoever - but still getting cold air on low seems strange.

If all functions as normal on low setting - might be worth checking the refrigerant pressure/quantities as if this is low it could be causing this problem - and would get progressively worse - as presumably there is a slow leak somewhere in the system. Not an easy task to do without spending some cash however - Kwik Fit recharge and lower your vent temp by 10% or money back (£44.95)- use same equipment as the dealer. Or Halfords - for the re-charge DIY gizmo with a pressure gauge - (£39.99 + FOC air con cleaner 'bomb'). This would be my first port of call.

Although you could always do a temperature test with a thermometer in the vent. Run the car, put air con on low and full fan - run for a few mins to let cool down. Stick a thermometer into one dash vent and shut the other three. Leave for a few minutes and check thermometer. If all is well with refrigerant should read somewhere between 6 and 10 degrees C. If not I would suggest leaving for a while longer and checking again if reading significantly higher than this - but still cool - suspect refrigerant levels. If reading nearer external temperature suspect more major fault.

Possibly next place to visit might be the interior temperature sensor (that is what is behind the circular grille on the climate control panel) at a guess if this is wonky then will be feeding wrong info to the climate control system with regards temperature in the cabin - so if you set to 20 and a wonky temperature sensor reads this as 14 it will heat up the air and spit it out. On low you are overiding the sensor which may explain why it works. - Hmm just convinced myself that this is more likely. Probably a trip to your dealer to get that checked out though. Good news is that I think this is a replaceable part and not part of the overall panel. Have alook on RealOEM.com Online BMW Parts Catalog (online parts catalogue).There are also a couple of temp sensors in the heater housing which may cause similar problems (again replaceable). Only way for sure is the dealer running a diagnostic check and finding the fault codes.

Just some ideas - and I'm no expert - although have just retrofitted the climate to my previously non-aircon car - so have a good idea of how the mini system goes together/operates.

Hope this helps.

Oh yeah and when you find the solution - make sure you let us all know.

[Root Ginger]

I have a feeling that the problem is being caused by the outside air temp sensor that has gone. Basically it's been gone for a while and reads -40 all the time (fail safe temperature). However I have noticed that recently with the hot weather it will read a temperature above -40. Anything from -39 to -10. Pretty much when it does this the Auto A/C starts pumping out hot air. I am getting a sensor from 1320 for £5 + VAT.

If this isn't it I'll start looking at the sensors in the Auto A/C panel itself.

[miniredcooper]

Hey root ginger,

looks like you have found the fault yourself - well done. Your original description of the problem didn't indicate a problem with the external temperature display - so presumed all was well - hence the series of alternatives.

As I'm sure you are aware - the climate system relies on information from a series of sensors to work properly - and yes the external temperature sensor is one of them and an intrinsic part of the functioning. If any one of these is providing the wrong information then you will have problems. So if this isn't functioning correctly then this could well be the problem.

Other sensors include the solar sensor (purple nipple on dash) - adjusts output dependent on sunlight intensity. The sensor in the control panel and the one on the heater box itself (monitoring internal temperatures). Although not likely to be at fault in this situation is the high pressure switch (in the pipework below the fuse box) which turns off the compressor and system when pressure in the pipework reaches a pre-determined pressure and clicks in and out during normal operation of the system - if this was faulty - they normally jam in off position there would be no cooling whatsoever - although I believe these are much more reliable in the mini/BMW than they are in Audi/Volkswagen which tend to fry these with a certain degree of frequency.

Sounds like a cheap and easy fix at a fiver and a great place to start.

Let us know how it goes - and fingers crossed.

[Root Ginger]

Yeah I'll let you know. I will be pulling the sensor out so it doesn't receive any spurious readings until the replacement arrives. It's really odd that it works fine when at the fail-safe temp. It must just ignore the sensor until it receives what it thinks is a relevant temp.

[miniredcooper]

You're right - seems weird - but maybe on low setting it disregards all temperature sensors and just keeps shooting out the coolest air it can produce as it is not working to any particular temperature. What do you reckon?

[Root Ginger]

Quote: Originally Posted by miniredcooper (original)

You're right - seems weird - but maybe on low setting it disregards all temperature sensors and just keeps shooting out the coolest air it can produce as it is not working to any particular temperature. What do you reckon?

No I mean it works fine completely. Set it to 20 and it keeps the car at 20 but as soon as it goes up to -39.5 it starts blowing hot air out and the only option is to switch to lo then, which as you say overrides all sensors and goes on full cooling. I remember I tried this once in the Summer, to see just how cold the car got, but gave up after I got a massive headache from the cold air.

[miniredcooper]

Wow - an 'ice cream' headache from your air-con - that's pretty cool.

Now it definitely sounds like you're right and the external temp sensor is the one causing the probs.

Good luck

[Root Ginger]

Quote: Originally Posted by miniredcooper (original)

Wow - an 'ice cream' headache from your air-con - that's pretty cool.

Now it definitely sounds like you're right and the external temp sensor is the one causing the probs.

Good luck

Yep, a full on brain freeze

[miniredcooper]

How did you get on?
Had a chance to get the temp sensor sorted yet.

[Root Ginger]

Ordered a new temperature sensor, tried to get the old one out without removing the bumper but there wasn't enough slack on the wire. So I put it back to try another time and now it's working perfectly!

The end result is that it was definitely the temperature sensor at fault. If it stops working again I'll swap it out.

In between all this though someone rear ended me. Not much damage but I have a BMW 116 to drive at the mo and my car is waiting to be picked up.

[miniredcooper]

Awww No. Hope the car isn't too bad - and sorry to hear you're slumming it in a 1 series.

On a more positive note - glad you got the air con sorted - one to remember I think.

[Root Ginger]

Quote: Originally Posted by miniredcooper (original)

Awww No. Hope the car isn't too bad - and sorry to hear you're slumming it in a 1 series.

On a more positive note - glad you got the air con sorted - one to remember I think.

Had a call from my accident management today and the bill for the repair is a minimum £1600. That's a lot considering it's a rear bumper, exhaust and a touch up of the bootlid.

[miniredcooper]

Ouch - that's a fair whack - but I bet most of it is in labour from swapping parts over (glass, wiper assembly, trims etc from one bootlid to the other and the ever expensive paintshop to paint the bumper and the bootlid.

If insurance are paying - then great. I reckon you could do that yourself for approx £300, using 2nd hand panels - might take you a while to get the right colour etc though.

[Root Ginger]

Quote: Originally Posted by miniredcooper (original)

Ouch - that's a fair whack - but I bet most of it is in labour from swapping parts over (glass, wiper assembly, trims etc from one bootlid to the other and the ever expensive paintshop to paint the bumper and the bootlid.

If insurance are paying - then great. I reckon you could do that yourself for approx £300, using 2nd hand panels - might take you a while to get the right colour etc though.

The bootlid isn't being replaced. Just a lick of paint. No damage to the metal at all just the paint. Bumper is being replaced, as is exhaust (non standard). Bumper is also Aero Kit and it has the arches body coloured too. Although not sure if the bodyshop noticed that???

I'm just using an accident management company, saves me paying the excess to my insurance in this open and shut case and will reduce the amount my premium goes up because of it. Accident, but no claim, pleases them immensely