I'm in the process trying to fix my a/c and my aux fans werent running at their low speed so i trcked that down to the resistor now when a jump the reciever-drier switch and let the fan run at their low speed the resistor gets really hot and i have already burned up one resistor and i am kind if hesient of putting the new one on for fear of burning it up also. I'm not buring any fuses or anything and the fans are pulling about 12.5 amps each at high speed. can someone help?

Resistors get hot, whats the problem (thats why they are surrounded by ceramics). They burn up every ten years in 5% of the vehicles, whats the problem.

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

mine burned up in 15 mins thats the problem.

Your fans seem about right current wise. The resistor should be able to handle that load. Where did it burn through? Was it at a connection?

Look at some figures: V=IR. During high blow you have 25a current. Figure 12.5v and the usefull resistance of the motors is .5ohm. The resistor is usually .2 ohm so the circuit with the motors and the resistors will have .7ohm and the current should be 17.85a. Now if you go straight to ground (say because one of the screws is too long and goes to the fender) then the circuit is 12.5=.2R, R=62.5a. Which one do you have?

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician

the resistor burned at the connection it turned black abound the area where you screw the wires into it. and it also smells has if it's burned. also while it was runing the usually black bracket was turing blue because of the heat.




as far as the this: "Now if you go straight to ground (say because one of the screws is too long and goes to the fender) then the circuit is 12.5=.2R, R=62.5a. Which one do you have?"



i'm lost.
could it have been a bad resistor.

the resistor burned at the connection it turned black abound the area where you screw the wires into it. and it also smells has if it's burned. also while it was runing the usually black bracket was turing blue because of the heat.




as far as the this: "Now if you go straight to ground (say because one of the screws is too long and goes to the fender) then the circuit is 12.5=.2R, R=62.5a. Which one do you have?" i'm lost.

Since you seemed to be able to measure the current through the motors at high speed, I did the math to tell you how much current you should be drawing through the resistor if the motors are in the circuit or if the circuit goes to ground after the resistor Seventeen amps or 62 amps. So I asked which case do you have?

__________________
Steve Brotherton
Continental Imports
Gainesville FL
Bosch Master, ASE Master, L1
33 years MB technician