Driving around 70mph on a 25 mile motorway run I engaged the air con - odourless smoke/steam came from the air vents.
Switched off the air con and re-engaged a minute or so later with same results - very visible to all occupants.
When I got it home I tried air con again and no smoke + it was chilling as normal
Would anyone know what was happening?
(Historically, I have owned the bus (92 Hiace Supercustom)5 months - had it re-charged and a minor pipe seal renewed -
A month back I nipped up an external joint which was dribbling. I have occasionally heard an odd buzzy noise through the vents for a short while when using it.
Usually only operate it for short bursts on short journeys.
Last time I looked the electric cooling fans for the air con rad were working OK - though I wonder how much of a 70mph wind blowing over them can be sucked downwards by the fans?)
Any pointers gratefully recieved
Chris
- (#9478) chris turner, 8 Jul 03 16:49
Hi Chris
What’s happening here is sort of normal. Cold dry air from your air conditioning is meeting hot humid air in the cabin. The result is that the moisture in the hot air is condensing when its cooled by the cold air. This is similar to the “steam” produced by breathing out on a cold and frosty morning. My guess is that when you saw the steam, you probably had a number of passengers. When you checked it at home, all the passengers had opened the doors and left, then the moist air in the cabin would have escaped out of the doors.
The air conditioning fans draw air up through the condensing radiators, not down. This actually helps the cooling, as it fools the viscous coupling into thinking that the engine is hot. The result is that the engine fan engages sooner, and for longer, which in turn helps the air conditioning fans to draw the air through, and adds to the engine cooling under increased load.
Hope that helps
dave Bright
- (#9479) dave Bright, 9 Jul 03 1:49
Thanks Dave
The windows were shut - though only occupants were wife and 3 yr old + myself. The major concern was that all the vents are set to cool the child so seeing plumes of 'smoke/gas/steam' engulfing him was a bit worrying.
The engine actually runs hotter (couple of degrees) with air con on. Atribute this to the extra load on engine which is very noticable especially when cruising 30-40mph.
Was under the impression that the extra rad only housed the air con gas/fluid and contained no engine coolant. Am I wrong here?
Thanks for pointing out which way the fans blow -
At the time I wondered if the higher engine temp/speed had meant the air con fluid had got so hot it had blown a joint with the pressure
Thanks again Dave - I am less worried now and will keep an eye on it
Chris
- (#9480) chris turner, 9 Jul 03 6:52
Hi Chris.
No your not wrong, I have got into trouble before for assuming that we are talking Townace’s twin radiator cooling system rather than Hiace’s cooling system, but the extra rad is air conditioning, not engine cooling.
When the air conditioning is on, the heat from the condensers, (extra radiator) is drawn into the void that feeds the air flow to the engine cooling radiator and viscous coupling. This extra heat is what fools the viscous coupling into thinking the radiator is hotter that it actually is.
At low engine revs the engine fan will not be turning very fast, so an increase in temp would be normal due to the extra load on the engine. At higher revs the fan is turning quicker, thus is cooling more, and should result in normal or slightly reduced temperature readings, despite the extra engine load.
By the way, was the air flow set to re-circulate within the car? If you are still worried, and I see your point about the three year old, it might be worth finding a local air conditioning specialist. They will be sure to know what it is.
Dave Bright.
- (#9481) dave Bright, 9 Jul 03 8:19
Re-circulate was off - a hot humid day though - I'll try and duplicate the conditions (minus the child) to see if it happens again
How it could affect the viscous is interesting as it is'nt spinning with the roar it did despite higher temps recently - I'm just about to remove the new toyota 88c stat tomorrow and try another as don't like the operating temp - (saw 107c recently though in real terms it could have been 103-4 due to accuracy of multimeter) - hot days on the motorway see 100c easy - whereas the old stat never went over 95c and only hit that when pushed hard - (glad I havent got an alloy head version)
Thanks Dave - I'll get on the case and phone up the local aircon firm
- (#9482) chris turner, 9 Jul 03 19:15
When I run my air conditioning I have it set on re-circulate.
This is because the air conditioning can only reduce air temperature by a few degrees, so using air that has already been cooled results in lower air temperatures. The drawback here is that some of the moisture in the air is lost during the cooling process, so the air becomes progressively drier the longer its on.
If the airflow is set to outside, it wont dry out to much, but you will only get the benefit from one cooling pass. Also, the air conditioning will have to be on for longer periods, and if its a humid day, then you are likely so see this “steam” effect. I saw this my self in a taxi in Tokyo some years back. It was over 100°C and about 80%relative humidity, so the taxi driver had taped a couple of pipes to the dash board in front of the air vents, with the other end resting on the back of the front seats. Now obviously this was to allow his passengers the direct benefit of the air conditioning, but to us it looked like it was an attempt to gas them.
dave Bright
- (#9483) dave Bright, 10 Jul 03 2:08
Thanks for the tip of having the re-circulate on - tried it today - got really chilly!
Got the steam effect again - only happens at or above 65mph a few seconds after switching it on - changed the stat (seperate post) - temps now much better - the toyota one was sticking and very sluggish
- (#9598) chris turner, 10 Jul 03 16:27