Heater burning smell

[bd1308]

For some reason I've been struggling to figure out what is burning in my HVAC system. I know that there might be a fan resistor inside the HVAC box that might have stuff on it (but there's also a very visible resistor setup on the passenger side firewall that I'm assuming goes to the ACC) or it could be some junk on the heater core burning. I'm not leaking coolant as far as Im aware and thus far I haven't leaked much oil at all. This smell almost smells like burning leaves, but I'm not really ready to take apart the 300D to get the HVAC box out...yet.

Any thoughts?

The fan makes no noise like bearings, just the smell sometimes drives me nuts.

[Sygma6]

It could very well be burning leaves. I am not 100% sure but I know leaves build up in my 300SD. Check to make sure that there is no buildup around the firewall.

[giff]

Check driver's side between firewalls. There's a large power resistor down in there, where I had smoke coming from burning leaves. Pretty easy to access by hand or mechanical fingers.

[vstech]

Originally Posted by bd1308

For some reason I've been struggling to figure out what is burning in my HVAC system. I know that there might be a fan resistor inside the HVAC box that might have stuff on it (but there's also a very visible resistor setup on the passenger side firewall that I'm assuming goes to the ACC) or it could be some junk on the heater core burning. I'm not leaking coolant as far as Im aware and thus far I haven't leaked much oil at all. This smell almost smells like burning leaves, but I'm not really ready to take apart the 300D to get the HVAC box out...yet.

Any thoughts?

The fan makes no noise like bearings, just the smell sometimes drives me nuts.

well, since you are discussing a 123 vehicle, not a 126, it's not the false firewall/leaves issue...

and since you have the resistor pack on your fender, it's not something like that, but it's POSSIBLE there is something in the windshield wiper motor area causing the smell.
more likely, there is an acc short from the aux pump being siezed... unplug your aux pump NOW and investigate your acc before it burns your car to the ground...

[bd1308]

Hmmm...It's an easy enough fix. I'll unplug it and see if that helps. Is there any chance a W123 could have a blocked heater core filled with dust/grime/etc?

[vstech]

Originally Posted by bd1308

Hmmm...It's an easy enough fix. I'll unplug it and see if that helps. Is there any chance a W123 could have a blocked heater core filled with dust/grime/etc?

not just a chance, it's a certainty... but it would only put out less warmth... not a burning smell...

[bd1308]

Tonight i'll unplug the Aux cooling fan and see if that makes a difference. It's been this way for over a year, so if it is the ACC board slowly frying I'm amazed it works at all.

[mkrazy1]

Originally Posted by bd1308

Tonight i'll unplug the Aux cooling fan and see if that makes a difference. It's been this way for over a year, so if it is the ACC board slowly frying I'm amazed it works at all.

As vstech stated, unplug the aux pump, not the aux fan. The pump and sieze and I believe cause the hvac board to overheat and cause a fire. There are a couple of pictures on this site of members cars burning up because of this.

[bd1308]

Yeah I meant that --- the pump. I didn't get a chance to unplug it last night, but i'm driving it tomorrow so i'll unplug it tonight.

Now my aux pump still runs, but the bearings are in the process of going bad, so I'm just going to unplug it and see what happens.

Dont know if a old pump will cause it to overheat, but it seems like that might be happening here. I had no idea it'd be enough to burn a car down -- usually it just fries the board.

I have *plenty* of air flow through the heating system (it just goes all up due to all of the vac pods being messed up (or one of them)) so it might just be the pump.