Please help: Troubleshooting Aux Fan Short R129

[R1990]

Hello everyone/ I've got a 1990 300SL-24 with a short circuit problem in the auxilliary fan circuitry. Basically, everytime the aux fans would come on, either by A/C or water temp, the aux fan fuse will blow immediately. I checked the wiring on both fans and nothing seems to be out of place or grounding anywhere. All insulation seems fine. Im a bit challenged when it come to electrical issues so I would appreciate if someone could help me out. Does anyone have a wiring diagram for this application? I was thinking as a last resort, just to re-wire the aux fan system but I would need a wiring schematic to do so. Where would be the most likely place that a short would take place? I think that a 1990 -up 300CE or 300E would be similar since we share the same engine? If anyone has any advice or suggestion, please post. Thanks in advance

[Arthur Dalton]

First suspect will be dropping resistor terminals ...

also, hand spin the fans for binding..

[R1990]

Originally Posted by Arthur Dalton

First suspect will be dropping resistor terminals ...

also, hand spin the fans for binding..

Hello Arthur and thanks for the quick reply. The fans turn freely when spun by hand. As far as your first suspect, forgive me but what is meant by "dropping resistor terminals"? Do you mean that terminals are literally hitting something metallic? Would you mind guiding me as to where these are located? I used to have a 300CE and it had a ballast resistor (ceramic) which had two terminals. Are you referring to this? I was thinking about that yesterday but could not find any ballast resistors in the engine bay. Thanks again.

[Arthur Dalton]

Yes
Behind driver headlamp area ..check for poor connections at terminals
http://catalog.eautopartscatalog.com/mercedesshop/sophio/wizard.jsp?partner=mercedesshop&clientid=catalog.mercedesshop&baseurl=http://catalog.peachparts.com/&cookieid=1D00YU6RY1JL0RQTFV&year=1990&make=MB&model=300-SL-001&category=G&part=Aux.+Fan+Resistor

archieves -fan resistor

[hudsmore]

It should be just one resistor. Easiest access is to yank the driver's headlight out. There may be a gum wrapper in there as the terminals are exposed. Before I'd play there, hook the fan direct to a decent battery and see what kind of current draw there is with a decent ammeter. I'd suspect the fans are full-o-crud and need a good clean and lube. Check the brushes while your there and give a good spray with contact cleaner.

You might also look at the aux fan relay. It is in the relay box behind the fuse box. There are two long ones in a row, it is the back one.

[R1990]

Ok guys, time for an update. I took the headlight off and inspected the resistor. Nothing out of the ordinary, no frayed wires, no gum wrapper, nothing. Next, I unplugged the fans and jumped the two wires by the dryer as suggested. Checked the fan connector for current and there is current but the fuse isn't blowing. So by process of elimination, I have isolated the problem with the fans, or maybe just one fan. I spun the fans by hand and they turn freely. Assuming that there isnt any short with the fans, why would a free turning fan or fans cause the fuse to blow? Sorry if this is a stupid question but I am new to auto electrical issues. Thanks again.