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Troubleshooting & Technical Questions & ModificationsHave technical or modification questions about the Crossfire?
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Fan would not go on for Heat/Air, so I purchased a Blower resistor off of eBay in anticipation of needing a new one. Replaced resistor and no change. I ran a test on the 3 prong connector and power to the connector, and progressively higher volts from center white as I turned the fan speed control up. With the new resistor, there were 12.4 V going to the motor at all fan speed levels. Hooked up old resistor and volts were progressively higher as fan speed was turned up. I then took out the blower motor and bench tested. Rust on both ends of the shaft. Nothing at first, but after WD 40 got minimum amount of fan turning. Reinstalled with new resistor and nothing. Put old resistor back on and it worked, but even at high fan did not move much air. It looks like the new resistor is defective and I will return it, and I need a new fan motor. What does the braintrust on the Forum think?
Ebay has a new one for $99. HVAC Blower Motor 4 Seasons 75897 | eBay
Is this a Mercedes part and what is the Mercedes part number?
Thanks,
Pete Jones
Manassas, Virginia
2007 Roadster with 76,300 miles. 6 speed manual
Fan would not go on for Heat/Air, so I purchased a Blower resistor off of eBay in anticipation of needing a new one. Replaced resistor and no change. I ran a test on the 3 prong connector and power to the connector, and progressively higher volts from center white as I turned the fan speed control up. With the new resistor, there were 12.4 V going to the motor at all fan speed levels. Hooked up old resistor and volts were progressively higher as fan speed was turned up. I then took out the blower motor and bench tested. Rust on both ends of the shaft. Nothing at first, but after WD 40 got minimum amount of fan turning. Reinstalled with new resistor and nothing. Put old resistor back on and it worked, but even at high fan did not move much air. It looks like the new resistor is defective and I will return it, and I need a new fan motor. What does the braintrust on the Forum think?
Ebay has a new one for $99. HVAC Blower Motor 4 Seasons 75897 | eBay
Is this a Mercedes part and what is the Mercedes part number?
Thanks,
Pete Jones
Manassas, Virginia
2007 Roadster with 76,300 miles. 6 speed manual
That part is made in China, it says so on the label in the last pic.
I think this is the correct part - 202 820 93 42. CLICK for sample picture, price and option to buy just the motor. The motor you have should have the Mercedes part number on it.
My AC is staying on even with the car shut off. I found the fuse and pulled it. Could this be a symptom of a bad blower motor resistor?
Most likely it's the resistor. I had the same thing happen when water got in the vent when the drain holes in the windshield cowl got clogged and filled with water.
Most likely it's the resistor. I had the same thing happen when water got in the vent when the drain holes in the windshield cowl got clogged and filled with water.
Well back story: last week I did have water drain out the bottom of my dash into the passenger floor. And I still cant figure out where its coming from. How do I unclog the drain holes?
Well back story: last week I did have water drain out the bottom of my dash into the passenger floor. And I still cant figure out where its coming from. How do I unclog the drain holes?
Raise the hood
remove (if they are there) the caps on the arms of the wiper blades
remove the nuts holding the wiper blades on
remove the wipers
using a (T20 I think) Torx driver, remove the 6 or so screws holding that cover on that runs the width of the car under the wipers
vaccum out the leaves and crud you find in there (it will be obvious)
using a (T20 I think) Torx driver, remove the 6 or so screws holding that cover on that runs the width of the car under the wipers
You will also have to unclip the O2 sensor harness wires, and cut a tie wrap or two.
Also, when you start to lift up the cover, reach underneath and unplug the heated nozzle connector.
You can leave the nozzle hoses connected, just pivot the cover out of the way.
On removing the wiper arms : I have had luck just raising the wiper arms, then gently rock them up and down while pulling up at the same time. Some have had to use tiny pullers, I never have.
My AC is staying on even with the car shut off. I found the fuse and pulled it. Could this be a symptom of a bad blower motor resistor?
The fan will come on with the ignition OFF, it is used with the operation of the REST heating function. That means that the switch will get power from some constant power source, the REST button is on the dash, maybe that is a good place to starypt looking. The engine coolant pump will also run, can you hear it under the hood?
The REST button is in the heating/AC control panel on the dash so as that part has caused many problems in the past it is a good place to start.
Last edited by onehundred80; Sep 10, 2016 at 12:05 AM.
The fan will come on with the ignition OFF, it is used with the operation of the REST heating function. That means that the switch will get power from some constant power source, the REST button is on the dash, maybe that is a good place to start looking. The engine coolant pump will also run, can you hear it under the hood?
The REST button is in the heating/AC control panel on the dash so as that part has caused many problems in the past it is a good place to start.
Good catch, didn't think of that since almost no one ever uses it ( at least around here ).
BTW, I have a spare one of those pumps, it is not an "engine coolant pump", it is only for circulation through the heater cores while you are RESTing.
Good catch, didn't think of that since almost no one ever uses it ( at least around here ).
BTW, I have a spare one of those pumps, it is not an "engine coolant pump", it is only for circulation through the heater cores while you are RESTing.
It is an engine coolant pump because that is what it does, that is my description of it not its official name which I find is Recirculating Pump in the parts list or just plain Water Pump in the Service Manual.
The REST function is the only reason that I can see why the AC fan motor would get any power with the ignition OFF. There are two lights on the REST switch and I have not looked at what the top left one does for sure, the bottom right is on with the iggy OFF and the light goes OFF when the car starts if it was ON before.
OK, semantics. I was thinking "engine coolant pump" = pump that cools the engine, not in the broader term that it is a pump that circulates engine coolant.
The other light is the "recirculate" light, I think.
And I didn't know that "recirculation" was automatic :
Air Recirculation/REST
This mode can be selected to temporarily reduce
the entry of annoying odors or dust into
the vehicle’s interior. Outside air does not flow
into the vehicle’s interior. To select, press the
recirculation button. To cancel, press the recirculation
button again.
The system will automatically switch from recirculated
air to fresh air after approximately five minutes at
outside temperatures below approximately 40°F (5°C);
after approximately 30 minutes, at outside temperatures
above approximately 40°F (5°C); after approximately five
minutes, if the A/C button is pressed.
At high outside temperatures, the system automatically
engages the recirculated air mode for approximately 30
minutes, thereby increasing the cooling capacity performance.
Press the recirculation button again to extend the
recirculated air mode.
OK, semantics. I was thinking "engine coolant pump" = pump that cools the engine, not in the broader term that it is a pump that circulates engine coolant.
The other light is the "recirculate" light, I think.
And I didn't know that "recirculation" was automatic :
It should also turn off if the battery starts to get weakened too much, these cars are too smart for their own good.
How difficult is it to change the AC control unit ??
Any pics or advice on how this is done
Gary
Sorry I came to this thread late. I recall a post that explained how to repair this problem in the control unit without having to replace it. It had to do with a connection on the board. I will check around. Mine does the same thing if you turn the **** to fast.
That's the thread.
Post #35 above shows how to get to the unit itself. It is from a thread showing the Navigation radio install.
Here is the repair thread as a PDF. CLICK
Here is a How To PDF on removal of dash panel to get at the control. CLICK
Last edited by onehundred80; Sep 10, 2016 at 04:32 PM.
I'm having similar issues with odd/wrong or no blower speeds, but I'm curious if this can be related to my battery dying when the car sits for a few days. I'm asking if the resistor or some other blower related part(s) can drain the battery. Thanks y'all!
Yes, the "resistor" (It is really a PWM regulator) is powered by battery supply and has it's own ground. A defective 'resistor' (Damn, I hate called it that) can sink a bit of current and can even run the fan motor without being commanded to.
If you have doubts about it, just change it. They are cheap ($30 or so with shipping) and are a known failure item in these cars and numerous Mercedes products.
Search "Mercedes SLK320 Blower Motor Resistor" (prices range from $23 to over $400 for the same damn part). They plug in and I believe you need a #1 or 2 phillips and an 8mm socket to get to them.
It helps if you are in really good shape, cause they are accessed from under the dash.
Last edited by pizzaguy; Oct 24, 2018 at 06:42 PM.
Awesome pizzaguy. I appreciate the fast reply. Yeah, I struggled just changing the cabin air filter, but I'll power through this one, too. Thanks again! And no judgement for your poor choice of words!! LOL
Re: Blower motor resistor
