![]() The blower is not shorting, there is no relay, the b,lower is inadvertently turned on by the PCB. I think you are looking at this that it turns on/off the 12 volts.The 12 volts is always present. The blower is switched on/off by the CAN bus connector to the PCB. A 2 wire heavy connector for the 12 v and a small multi wire (I think there is 8 wires) connector. I don't think there a constant 12 volt power to the fan, so what is telling the circuit to send 12 volts power to the fan? Is there a switch or relay somewhere else that could be faulty? There is a constant 12 volts to the blower motor via the separate 2 wire connector. I am no electrician, but it seems to me that the only way the fan/resistor could short out and keep the fan running is if it had a CONSTANT 12 volt power source. I turn off the ignition, everything powers down, then 10 seconds later the fan kicks on and stays on until the battery is drained. Cleaned the lugs and the removable connectors and everything is fine. They are made from the same metal as the contacts in the tail ight sockets. The spade lugs and connectors are not conformal coated and have very small surface area for the high current connection. No hoild downs, screws, anything.just held in place. The regulator board is connected to the blower with 4 spade lugs. Then saw the issue.which might be the problem with most units. Even if were wet, there should be no impact. I saw the typical corrosion, but also noticed the board is also conformal coated. ![]() Removed the blower, area was dry and removed the 2 screws holding the cover in place for the regulator board (its not just a resistor, its a full board with many components). Thought I would change just the board since the blower was running which meant it's ok. Removed the blower motor and was searching E-Bay for a replacement. 2008 ML 550, blower runs with the key off. I thought I would pass this on for what it might be worth. ![]()
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