Climate control issue: no cabin air fan
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Climate control issue: no cabin air fan
I haven't been able to discern any pattern, so I'll just relate what happens.
In general: When first starting he car, all is well. Make a short trip, and park for a few minutes. When I come back there is no cabin air blower. I've tried manually changing fan speeds, turning climate control off and back on, and shutting the car off and restarting it. I even tried switching to heat and defrost. Nothing seems to work. I think it may be just the fan because you can feel a little "coldness" if you hold your hand over the vent while driving. If you drive long enough and fuss with it enough, eventually it comes back on. I have yet to have it come back on if just left alone (leaving it alone is tough to do in 90 degree weather...). Once it hadn't come back by the time I got home. Every time it has sat for at least an hour or so it works normally.
All panel indications are "normal". When you manually set the speed it shows the expected speed even though the fan is not running.
I have yet to have it quit while it was working, although I think there was one case where fussing with it got it working, and further fussing caused it to quit again, in a matter of seconds.
There were two times when it didn't quit after the first stop, but did after the second. Some first trips are "long": more than 10 minutes, others are short: under a mile.
Not sure where to start; any suggestions appreciated.
In general: When first starting he car, all is well. Make a short trip, and park for a few minutes. When I come back there is no cabin air blower. I've tried manually changing fan speeds, turning climate control off and back on, and shutting the car off and restarting it. I even tried switching to heat and defrost. Nothing seems to work. I think it may be just the fan because you can feel a little "coldness" if you hold your hand over the vent while driving. If you drive long enough and fuss with it enough, eventually it comes back on. I have yet to have it come back on if just left alone (leaving it alone is tough to do in 90 degree weather...). Once it hadn't come back by the time I got home. Every time it has sat for at least an hour or so it works normally.
All panel indications are "normal". When you manually set the speed it shows the expected speed even though the fan is not running.
I have yet to have it quit while it was working, although I think there was one case where fussing with it got it working, and further fussing caused it to quit again, in a matter of seconds.
There were two times when it didn't quit after the first stop, but did after the second. Some first trips are "long": more than 10 minutes, others are short: under a mile.
Not sure where to start; any suggestions appreciated.
Last edited by John CC; Jul 24, 2023 at 03:52 PM.
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
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2011 GLK 350 4Matic
Good chance that'll work. The brushes get worn down to the point they're very intermittent, and often that whack with a semi-solid object will jar them back into position enough to get the motor working again (for a very short time, of course).
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
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2011 GLK 350 4Matic
That applies to the rest of the vehicle as well - I'd suggest that most 84,000 mile GLKs in NYC (or similar) are looking and acting "well-used" barring extraordinary maintenance, while those like mine (garage queens from the desert southwest) will look and drive like nearly new cars.
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Just a quick update.
Since the heat wave has ended, it hasn't occurred once, so, I'm thinking it has to do with something getting heat soaked. I am a total klutz with WIS, and can't figure out how to get a schematic of the blower circuit. (I found something, and it seems to show I have two blowers, which I don't think is correct.) Regardless, it shows a solid state controller. Wonder where that is?
The cabin temperature was lower after the brief stop than it was on the initial start, so I'm wondering if it isn't a component in the engine compartment that is failing, or a component that generates heat while the system is running. Any guesses?
Since the heat wave has ended, it hasn't occurred once, so, I'm thinking it has to do with something getting heat soaked. I am a total klutz with WIS, and can't figure out how to get a schematic of the blower circuit. (I found something, and it seems to show I have two blowers, which I don't think is correct.) Regardless, it shows a solid state controller. Wonder where that is?
The cabin temperature was lower after the brief stop than it was on the initial start, so I'm wondering if it isn't a component in the engine compartment that is failing, or a component that generates heat while the system is running. Any guesses?
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2021 GLB250 FWD, 2023 GLA250 FWD, 2013 C250, 2015 GLK350, 2005 ML350SE, 2003 E320
The blower motor controller sits right to the left of the motor when looking forward. The red and yellow wires (on a GLK350, at least) from the motor plug into it.
Just be aware that the problem could have originated in the fan speed controls above the console. I had to replace mine at some point. There are plenty of good used ones available on eBay. It displayed what looked like the right settings, but it just didn’t have correct outputs. The fan ran on high and driver side temp was high heat regardless of settings.
Just be aware that the problem could have originated in the fan speed controls above the console. I had to replace mine at some point. There are plenty of good used ones available on eBay. It displayed what looked like the right settings, but it just didn’t have correct outputs. The fan ran on high and driver side temp was high heat regardless of settings.
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2011 GLK 350 4Matic
Just a quick update.
Since the heat wave has ended, it hasn't occurred once, so, I'm thinking it has to do with something getting heat soaked. I am a total klutz with WIS, and can't figure out how to get a schematic of the blower circuit. (I found something, and it seems to show I have two blowers, which I don't think is correct.) Regardless, it shows a solid state controller. Wonder where that is?
The cabin temperature was lower after the brief stop than it was on the initial start, so I'm wondering if it isn't a component in the engine compartment that is failing, or a component that generates heat while the system is running. Any guesses?
Since the heat wave has ended, it hasn't occurred once, so, I'm thinking it has to do with something getting heat soaked. I am a total klutz with WIS, and can't figure out how to get a schematic of the blower circuit. (I found something, and it seems to show I have two blowers, which I don't think is correct.) Regardless, it shows a solid state controller. Wonder where that is?
The cabin temperature was lower after the brief stop than it was on the initial start, so I'm wondering if it isn't a component in the engine compartment that is failing, or a component that generates heat while the system is running. Any guesses?
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
I think maybe I'll run a pair of wires off the motor to an led somewhere visible as a monitor.
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From: Ottawa, Ontario
2013 GLK350 Canada
I had same issue last year
I took my fan assembly out and flushed it in rubbing alcohol last year (some will remember I wrote about this). I let it dry in the sun for an hour (don't want any fires, do we!) and it worked great after that. Brushes had loads of wear left after 225000 km. It has just started acting up again. Seems to start up after turning off for a few minutes and jostling it over a few bumps.
I think it is the motor bushings that are worn and not providing contact for current flow through the motor (had this exact issue in a GM starter years ago). You can determine this by removing the under dash cover and give it a little bump (haven't had the chance to do that yet). Checking for voltage is a good start, however. If voltage is present and a bump starts it, a cleaning might help for a while. It's amazing how much carbon brush crap gets stuck on the motor assembly in there! Not sure if the bushings are replaceable.
I think it is the motor bushings that are worn and not providing contact for current flow through the motor (had this exact issue in a GM starter years ago). You can determine this by removing the under dash cover and give it a little bump (haven't had the chance to do that yet). Checking for voltage is a good start, however. If voltage is present and a bump starts it, a cleaning might help for a while. It's amazing how much carbon brush crap gets stuck on the motor assembly in there! Not sure if the bushings are replaceable.
Last edited by KanataSteve; Aug 5, 2023 at 06:27 PM.
Thread Starter
MBWorld Fanatic!
Joined: Jun 2021
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From: New Hampsha
'17 GLS450, '14 GLK250, Grandpa's Roadster
Just a quick update:
I have done nothing since it started working again. The last 4-5 days we've been back into the 90's again, and it has continued to work as expected. I'm not complaining, but it doesn't give me that warm (no pun) and fuzzy feeling...
I'm planning to hook some test wires up to the fan motor when I replace the cabin air filter, but it's too hot right now...
I have done nothing since it started working again. The last 4-5 days we've been back into the 90's again, and it has continued to work as expected. I'm not complaining, but it doesn't give me that warm (no pun) and fuzzy feeling...
I'm planning to hook some test wires up to the fan motor when I replace the cabin air filter, but it's too hot right now...
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From: South Texas
2014 GLK350 base model (active) ; 2001 E320 base (retired); 2001 Wrangler soft-top
