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96 S420, 00 ML55
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78 Posts
Discussion Starter #1
At idle and slow speeds the AC in my 2000 ml55 was going warm. I discovered the fan was not turning. I bit the bullet as I need the truck running and bought a new fan. Everything is working again. In the replaement I discovered that the plug was mangled making it impossible to plug in the new fan. I had to graft a replacement plug on the leads to make the new fan work. I would like to test my old fan now to see if it still works when receiving the right signals. According to the information I can find the speed control is PWM from 10% to 90% duty cycle, but I havent found the voltage or frequency of the input signal to duplicate it with a pulse generator. Is it 12V or are the control signals stepped down? Does anyone have a reference of experience with these details?

Mike in ABQ
 

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1998 ML320
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136 Posts
Watching with interest. I have an ML500 electric fan, and I would like to figure out how to get the right signals to it to use in my 1998 ML320. I haven't really had time to dig into it yet.
 

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Dallas, Texas
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8,187 Posts
At idle and slow speeds the AC in my 2000 ml55 was going warm. I discovered the fan was not turning. I bit the bullet as I need the truck running and bought a new fan. Everything is working again. In the replaement I discovered that the plug was mangled making it impossible to plug in the new fan. I had to graft a replacement plug on the leads to make the new fan work. I would like to test my old fan now to see if it still works when receiving the right signals. According to the information I can find the speed control is PWM from 10% to 90% duty cycle, but I havent found the voltage or frequency of the input signal to duplicate it with a pulse generator. Is it 12V or are the control signals stepped down? Does anyone have a reference of experience with these details?

Mike in ABQ
Small connector has two wires. Blue from fuse F1f22 and white from engine control module. Signal is 10 Hz, voltage from 1-12.5 V. In case control signal is faulty or missing fan should go full tilt.
 

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Registered
96 S420, 00 ML55
Joined
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78 Posts
Discussion Starter #4
Thanks, Witek. That is just what I needed. I'll put some signal to it and see what happens. I'll report back with any useful information.

MikeinABQ
 
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