Mercedes-Benz Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
3 Posts
Discussion Starter #1
Help! I have a 1991 300D that keeps blowing the A/C-Heater blower motor fuse. The odd thing is that the fuse that keeps blowing is a 25amp and located in the "H" block in the fuse panel. This fuse also controls the rear windows. The fuse blows at different times, sometimes while I am driving, and now immediately when I turn on the ignition. It blows even when the ccu is in the off position. I disconnected the rear window switches and the fuse still blows. My fuse box says nothing about the "H" fuse controlling the blower motor. I can go days, months with no problem then all of a sudden it starts blowing the fuse. My blower motor makes no unusual noises. It acts like there is a dead short somewhere as the fuse pops immediately when the ignition is turned to the on position. Any help will be greatly appreciated.
 

·
Registered
W124
Joined
·
4,839 Posts
I think an easy way to isolate the regulator and blower as being the source of the short would be to remove the three pin connector that runs to the regulator from its socket on the firewall. The regulator is located directly under the blower but the three pin connector for the harness running to it is fairly easy to access just behind and above the power brake booster. If you lift this connector off its socket you will take the reg and blower out of the circuit. Should the fuse still blow you have removed the blower, regulator and related harnesses from the equation. If it doesn't blow you might want to drive a few days like this to see whether or not the short returns. This may not solve your problem but it will help narrow down your search.
 

·
Registered
Joined
·
3 Posts
Discussion Starter #4 (Edited)
Thanks for the reply and advise/direction. What is strange to me is the blower/regulator being tied in some how with the rear windows fuse. This should not be so. I downloaded the "91 wiring schematic to check the circuits. My car has the upgrade to the inline 30amp fuseable link that is supposed to bypass fuse # 12 in the fuse box. The "H" fuse is lists only the rear windows on it. I will disconnect the regulator as you suggested, isolating the dead short will certainly help me solve this problem.

I just tried it. Unplugged the regulator and fuse #12 blew as soon as ignition turned on. Also, for the 1st time, the inline fusable link started to smoke. Did not like having the regulator unplugged. Short must be in the window circuit?

Thanks again.
 
1 - 4 of 4 Posts
Top