I have an electric fan on my car it draws about 18 amps. When I first put it in I decided I did not want this circuit to fail so I used a 75 AMP heavy duty relay. Like this one.
Amazon.com: TE tyco BOSCH 75 Amp High Current 12 Volt Automotive Relay SPST: Automotive
After driving the car for about 6 month the relay exploded. We are talking shrapnel and the EMI effected the computers and shut down 6 cylinders. I had to limp it home 30 miles on 6 cylinders (This is a V12) and no fan. That is why I didn't want it to fail. Since that didn't work I replaced the relay with a standard 30 amp relay that you buy from pep boys for about $6.00. Its been working flawlessly ever since until now. Today I found the fuse blown. And I don't mean just blow as in pull out the fuse and replace it. I mean shrapnel and nothing in the pile of melted goo that remotely resembles a fuse. I think these events are related. Arcing across relay contact or arcing across a blown fuse. In both cases the possibility of fire was very evident.
In any case I did a little research and found that this is a problem in a lot of places. I found wire diagrams of circuits used to suppress arcing, consisting of a capacitor and resistor or zener diodes.
What I haven't found is the table that says for 12V at 20 amps use size X capacitor and size Y resistor and place between pins? and ??
Should such a device do on the relay contractors or across the motor.
It has only happened twice in about 8 years but it is a safety concern.
Does anyone have any suggestions.
Amazon.com: TE tyco BOSCH 75 Amp High Current 12 Volt Automotive Relay SPST: Automotive
After driving the car for about 6 month the relay exploded. We are talking shrapnel and the EMI effected the computers and shut down 6 cylinders. I had to limp it home 30 miles on 6 cylinders (This is a V12) and no fan. That is why I didn't want it to fail. Since that didn't work I replaced the relay with a standard 30 amp relay that you buy from pep boys for about $6.00. Its been working flawlessly ever since until now. Today I found the fuse blown. And I don't mean just blow as in pull out the fuse and replace it. I mean shrapnel and nothing in the pile of melted goo that remotely resembles a fuse. I think these events are related. Arcing across relay contact or arcing across a blown fuse. In both cases the possibility of fire was very evident.
In any case I did a little research and found that this is a problem in a lot of places. I found wire diagrams of circuits used to suppress arcing, consisting of a capacitor and resistor or zener diodes.
What I haven't found is the table that says for 12V at 20 amps use size X capacitor and size Y resistor and place between pins? and ??
Should such a device do on the relay contractors or across the motor.
It has only happened twice in about 8 years but it is a safety concern.
Does anyone have any suggestions.