Air Con blowing cold air only

[juicestop]

Hi All

Drove the car (IS250, 66k miles) today and air con was blowing cold air only. I have the air con set to 23 degrees and rarely change this unless the weather is hot. I checked the coolant level and it was below the minimum mark so topped up with the recommeded coolant. However, after a 20 minute drive the air was still blowing cold. The dash board temperature meter was normal at just under halfway. I checked the coolant level again and it was still at the max mark that I previously topped up to. I did notice that the radiator fans were on. Does anyone have any idea as to what the problem may be? Any help would be greatly appreciated.

[normski2]

The best thing to do when you experience this is to turn up the temp a few degrees at a time until you reach a point where the introduced air starts to get warmer. At least this will indicate all is well.

It's worth remembering, it may be warmer in the car than you think it actually is, which will result in the system blowing colder air to reduce the interior temp back to its chosen (23) setting.

I know it may sound odd but I proved this point to my wife the other morning driving in to work. She had turned down the temp setting a few degrees and then wondered why her legs were feeling cold air. It was pretty cold outside but the car had been in early morning sun, albeit not hot sun. It was still enough to elevate the interior temp above the setting.

Hope that helps.

[juicestop]

Thanks Normski. I already tried increasing the temp as you advised, all the way up to High. Believe me, the air con was blowing out really cold air. Outside temperature was 7 degrees centigrade and it has been cloudy and raining all day. Yesterday the air con was behaving normally, today just cold air and hadn't touched any settings.

[madasahatter]

Sounds like a stuck thermastat, or i believe they have a heater control behind the dash. Some body with more knowledge may know different.

[lex28]

I had the exact same issue last month but my coolant looked low, possible leak..but after topping it up a litre it's back to being warm again. 

You could possibly have a jammed theomstat..

 

[juicestop]

Thanks for your responses guys. Checked the coolant bottle level that I topped up last night and it has gone lower a little bit. I think this is normal when the engine cools. However I'm still not getting any warm air in the cabin, the temperature guage on the dash is still at normal (just under halfway). One thing to note, when I started the car this morning after checking the coolant level I noticed the radiator fans were on. I guess this points to a faulty thermostat, I've just ordered a new one. I can live with the cold air for now, but is it safe to run the car like this or would I risk engine damage if it is a faulty thermostat? My mechanic can't look at the car until Monday.

[madasahatter]

Fans only come on when the air cons on. You could try taking cap off expansion bottle, and run car upto temp. You may have an air lock, Squeeze

the pipe at top of rad. 

 

[johnatg]

It's hard to see how this has anything to do with the thermostat - if it was stuck open the heater would still be a bit warm and the temp gauge would show low.

It is either an airlock, preventing coolant from getting to the heater matrix - check the pipes to the heater (at the back of the engine) - they should be hot to touch at all times the engine is hot - if not you have an airlock.

Or it could be the heater controls - there's an ecu which controls motors to arrange airflow to mix hot and cold air as required. Something could be wrong there.

But as this followed a low coolant situation, I'd go for the airlock. Try cautiously disconnecting hoses in the coolant system and see where coolant or air escapes.

[normski2]

Think John is on the right tack here.

You mentioned the coolant was low so there may be a stack of air fed to the heater matrix for the interior heating. I had this on my is200 years ago. I'm struggling to remember exactly what i did to bleed it. I'm thinking there was a bleed screw on the matrix itself. Trouble is I may be recalling a similar thing I had on a Nissan.

I'll get my coat!

[juicestop]

Thanks everyone for your help. It was an airlock. The solution was to top up the expansion bottle when cold, I did this 5 times over 5 days. I also squeezed the pipe at the top of the radiator and today back came the warm air. I have also checked pipes and looked under the car for obvious leaks but could not find any, but I'll be keeping an eye on this for the next few days as it's a bit of a mystery as to why the coolant level went low in the first place. I did (needlessly now) order a thermostat, but for £35 I guess its good to have a spare one just in case...

[madasahatter]

Glad your all sorted, cars can be a mistery sometimes. Not a bad price for the stat.

[juicestop]

Yes not a bad price, that's why I ordered it just in case that was the problem. Not an OEM part obviously at that price.