Terrible Heater and AC Smell

C

clintman17

Member
 Alexandria, VA
I'm having a terrible smell come out of my vents when I have the heater or AC on. It seems to go away after a while with the AC, but the heater never seems to stop. It smells like burning plastic.

Any suggestions on what to check? I already changed the cabin filter, but the symptoms still persist. :thumbsdown:

Thanks for your help.
 
I had a similar problem with the wife's Rover 45 a couple of years ago.
It was the heater module on top of the fan under the glove compartment.
Resistors fail and it over heats - smell was awful. Burnt plastic/dead fish
In this case there was also smoke coming out for a while
As a safety measure the fan usually speeds up (or you lose the slower fan speeds).
£300 for new one or £0.75 for 2 resistors of Maplin and 20 mins work
 
I'd be looking at a fault in the final stage resistor. Sometimes called the 'hedgehog' as this is a burnig smell, therefore something getting very hot.

Most other issues of odour relate to putrid washer water, soggy or clogged pollen filters, etc. but are very different smells.
 
by cj10jeeper » Wed Nov 06, 2013 11:20 am

I'd be looking at a fault in the final stage resistor. Sometimes called the 'hedgehog' as this is a burnig smell, therefore something getting very hot.
Click to expand...

That was the thing - looked liked a series of aluminium pens stood in rows. the heating elements were inside and turned on in accordance with the heat setting you choose.
I can smell it now :(
When mine failed the blower came on full in an effort to cool it down
 
clintman17 said:
I'm having a terrible smell ..... the heater never seems to stop. It smells like burning plastic....
Click to expand...
I have the exact same thing. Cannot figure it out but its only on the passengers side.
 
Yes - on the Z4 it's on the passenger side.
Other symptoms include fans switching on randomly or as happened with mine starting up when the car was locked and just draining the battery.
 
So, do I reach this resistor from the interior of the car? From the description it sounds like it could be right around where the cabin filter is located?
 
This should help, it's the "N2" part
GREO_E85_64_0009.png
 
Thanks bcworkz, and everyone else, I'll investigate further. Is there a way for me to look at it and know if this is the problem?
 
If you don't have aircon then it doesn't happen but if you do then mould/fungus can grow in your air con system. I had it with a five series BMW, solution is you can buy an air con cleaner in a can, you stick the can in the middle of the car, engine & aircon running, all windows shut tight with the heater set on recirculate. Set the can off & shut the door quick, it emits some sort of poison/bug killer into the air which is sucked through the aircon system killing all the bugs & getting rid of the smell. no new parts needed!
 
Chuffer said:
If you don't have aircon then it doesn't happen but if you do then mould/fungus can grow in your air con system. I had it with a five series BMW, solution is you can buy an air con cleaner in a can, you stick the can in the middle of the car, engine & aircon running, all windows shut tight with the heater set on recirculate. Set the can off & shut the door quick, it emits some sort of poison/bug killer into the air which is sucked through the aircon system killing all the bugs & getting rid of the smell. no new parts needed!
Click to expand...

That's fine for mould and related smells from filters and aircon, but this is a burning smell so would seem unrelated.
 
Honestly, I don't think it's the blower speed control. This is not the classic "hedgehog" resistor pack many of us older members know well. It is an electronic speed control that is not subject to the kind of currents going through traditional resistor packs. In addition, if the odour is actually coming through the vents, you can see this part is not in the airflow path.

Do give it a look for heat damage, easy enough to do, but don't be surprised to find it quite normal looking. Unfortunately, I don't have a better suggestion. I can't think of anything electrical that would get into the air ducting itself. Perhaps the blower motor? Maybe the bearings are going bad, increasing the load, causing the the windings to cook off a bit? Just a crazy guess. Good luck with this, sounds like quite the puzzle.
 
BCW - Agree with you. Burning that doesn't stop is an odd one. Usually find things die quickly in a puff of smoke or a bang of a fuse. If be using some old fashioned nose investigation under the dash, under bonnet, etc. to find a source.
 
Yeah, kind of sucks. I think I'll just have to have someone look at it. The smell definitely comes through the vents and, no matter how long I have it on, it still smells.
 
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