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hot smelly air when in recirc mode

Posted by nomis3613 
November 11, 2010 04:52AM
Hi,
I've noticed that when I put the ventilation into recirculation mode its quite warm (and definitely warmer than the cabin temperature), also it has that "old aircon" smell (even when the aircon is off).

Any idea what the cause is?

I'll be replacing the stereo soon, I'm thinking it'll be good to get this sorted while I'm poking around the centre console anyway.

Thanks,
Simon
rkj
November 11, 2010 11:34AM
Quote
nomis3613
Hi,
I've noticed that when I put the ventilation into recirculation mode its quite warm (and definitely warmer than the cabin temperature), also it has that "old aircon" smell (even when the aircon is off).

Any idea what the cause is?

I'll be replacing the stereo soon, I'm thinking it'll be good to get this sorted while I'm poking around the centre console anyway.

Thanks,
Simon

Unfortunately, our cars do not have cabin filters and the heater plenum can be entered by mouse' and then they take a pee (if that's what you're smelling) and can get trapped. Ask me how I know, but that's another story! It sounds like you just a musty old smell coming from the heater/ac system. You could try spraying some Lysol, or some such product, in the intake while the fan is running. That might clean things up a touch, I've had pretty good luck with fabreeze too.

My 323 baur I had to replace the top heating/ac plenum cause we just couldn't get the stink out and the pee had etched in to the plastic- yuk
rkj
November 11, 2010 11:38AM
Quote
rkj
Quote
nomis3613
Hi,
I've noticed that when I put the ventilation into recirculation mode its quite warm (and definitely warmer than the cabin temperature), also it has that "old aircon" smell (even when the aircon is off).

Any idea what the cause is?

I'll be replacing the stereo soon, I'm thinking it'll be good to get this sorted while I'm poking around the centre console anyway.

Thanks,
Simon

Unfortunately, our cars do not have cabin filters and the heater plenum can be entered by mouse' and then they take a pee (if that's what you're smelling) and can get trapped. Ask me how I know, but that's another story! It sounds like you just a musty old smell coming from the heater/ac system. You could try spraying some Lysol, or some such product, in the intake while the fan is running. That might clean things up a touch, I've had pretty good luck with fabreeze too.

My 323 baur I had to replace the top heating/ac plenum cause we just couldn't get the stink out and the pee had etched in to the plastic- yuk

I forgot to add; I think the fact your warmer temp air is natural on recirc if the ac isn't on, it's just taking the same cabin air and rerouting it through the system, warming it as it goes through, and sending it back out to you..... I think. Lets see what the other guys have to say.
November 11, 2010 01:09PM
Quote
rkj
I forgot to add; I think the fact your warmer temp air is natural on recirc if the ac isn't on, it's just taking the same cabin air and rerouting it through the system, warming it as it goes through, and sending it back out to you..... I think. Lets see what the other guys have to say.
I agree. With fresh air, the heater is warming up (usually) cooler outside air. On recirc, the air is coming from inside, where it has a higher starting temperature, so it gets warmed up more. (It's also likely to fog up the windows, which is why I never use it except when the A/C is on.)

__________
Dave
'91 325iX
November 11, 2010 04:15PM
Thanks for the help. Just to clarify even without the heater on (it's summer over here now...finally...) the recirc air is warmer than fresh air mode.

Which intake should I spray the Lysol etc into? If I also have some decomposing wildlife in the heating plenum how do I get to it?
rkj
November 11, 2010 05:47PM
Quote
nomis3613
Thanks for the help. Just to clarify even without the heater on (it's summer over here now...finally...) the recirc air is warmer than fresh air mode.

Which intake should I spray the Lysol etc into? If I also have some decomposing wildlife in the heating plenum how do I get to it?

The recirc is just a closed loop that shuts off outside intake air and takes the inside air (from the cabin) and runs it through the system (cold or hot or neutral, heat, ac or just outside/inside temperature) and then out to the cabin. That's why the factory sez don't run it longer than 30 minutes at a time; the air just turns foul after a certain time.

Under the center of the cowl after you open the hood the heater/ac system core intake sits, it's under the heater motor (I think, it's been awhile since I've been in there). If you have the heater going (with all the levers pushed to the right a touch) the system should suck whatever you're spraying if you aim it under the center covering metal plate (not the one on the firewall (vertical) for the wiper motor that's screwed down), but the welded in one by the lower windshield molding rubber seal, on the horizontal.

If the air you're smelling is just a musty stale one, That should be easy to clean up. If an animal has died in there it's another story. You'll have to get to the inside of the core; The other side!

If the later is true it will stink badly when you turn on the upper vents on the dash; it's an unmistakable stink that's awful and it will probably never go away no matter what you do. Like my 323, you'll have to replace the upper phlegm assembly.
November 11, 2010 11:15PM
I am having just the opposite issue, but I think I know what it is, bad seals for the HVAC recirculate flaps. This pic might help you see what it all looks like:



My thoughts, in your situation, are that you need to remove the dash and do a thorough cleaning. Yeah it will suck, but don't feel alone as I'm going to be pulling mine (again) to put new foam in for the evaporator, run some wiring, and convert to a parallel flow condenser for better AC performance. I think also that the warmer air you are getting in the cab with the recirc on is just what has been described; the higher ambient temp in the cab being reflected.
November 11, 2010 11:20PM
Thanks for the diagram. I was struggling to picture how it all works, so it's really helpful thanks.
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