93 240 fuse 12 blowing (windows,ac relay,seat belt light) Topic is solved

[CoreyT]

I just purchased a used 240 Sedan for my son knowing that the power windows did not work. Everytime we replace fuse #12 and turn on the ignition the fuse blows. Its winter now, but he won't have Air or be able to open the windows when it gets hot. Any suggestions? I have read in some other models that a short is possible, but where do we look 1st. Any help would be greatly appreciated

[LaRy]

This is not easy! You must get some simple meter to check the resistance. Connect it to the outgoing side of the holder for the blown fuse and ground. Outgoing side is easy to check, when ignition is on and fuse is out you do not have any voltage at that side. Now (without ignition on) you will get some resistance to ground, any value less than 0.8 ohm will blow the fuse!

The principle in finding a short circuit is to disconnect components and see when the resistance value is getting high(er). Straight on the fuse you have minimum two bl-y wires. One wire is feeding the windows and the other is feeding the revrese gear switch for the light and the AC relay.
Disconnect first bl-y wire then try the other one and check when the resistance value increase. Now you are closer! Keep that wire off.
Now something will not work (and the fuse will not blow) and you are closer to the problem. If it helps to take out the AC wire, take out the AC relay and see if it help, if not continue to look for the reverse gear switch. My personal guess is that it is something with the switch assembled on the gear box. The enviroment is not to good under the car. Follow that wire and look for damage. Eventually just cut it to test if the problem will disapear.

[CoreyT]

My son found the short under the center console. The console had some damage to the plastic and he found a bare wire touching metal underneath. Everthing works now. Thanks again for your help.