what causes cooling fan relay failure

[bkozlow]

Generally, it is three words written on the relay "MADE IN CHINA" and if it is Bosch then your amp rating is to low. I would go to a German car dealer in your area and have the parts department find you a HD unit for one of their top model cars, more than likely they will be Bosch no matter what type car. Or you can contact Texas Industrial Supply at texasindustrialelectric.com/relays and look over their inventory. Look at 0332-002-168, if it were to fail then you have other problems in your system.

Bill K

[ERA 626]

Originally Posted by bkozlow

Generally, it is three words written on the relay "MADE IN CHINA" and if it is Bosch then your amp rating is to low. I would go to a German car dealer in your area and have the parts department find you a HD unit for one of their top model cars, more than likely they will be Bosch no matter what type car. Or you can contact Texas Industrial Supply at texasindustrialelectric.com/relays and look over their inventory. Look at 0332-002-168, if it were to fail then you have other problems in your system.

Bill K

he beat me to it... "made in CHINA" all joking aside you cant simply throw a higher current relay at the problem. If that is the case than you will need to confirm that the size wire/fuse is of the correct size to handle the load of the fan as well or bad things may happen. Better safe than sorry. Sorry I am an electrician by trade.

[RallySnake]

There is another alternative. Simply wire a second 40 amp relay in parallel with the first. They share the load and last much longer. Also a big capacitor helps smooth out the voltage fluctuation.

RS

[patrickt]

Originally Posted by RallySnake

There is another alternative. Simply wire a second 40 amp relay in parallel with the first. They share the load and last much longer. Also a big capacitor helps smooth out the voltage fluctuation.

RS

Not only will they share load, they will shift load as well. As one relay heats up, and resistance increases, current will automatically flow down the alternate path. For a fun bar room bet, have two parallel paths serving the same 30 amp load. If all things are equal, fifteen amps will flow down both paths. But if you put a five amp fuse on one leg, the fuse will not blow because the increased resistance of the heated up fuse will send the current down the other leg. The same holds true for a one amp fuse. All magically done with no user intervention.

[cycleguy55]

Originally Posted by patrickt

Not only will they share load, they will shift load as well. As one relay heats up, and resistance increases, current will automatically flow down the alternate path. For a fun bar room bet, have two parallel paths serving the same 30 amp load. If all things are equal, fifteen amps will flow down both paths. But if you put a five amp fuse on one leg, the fuse will not blow because the increased resistance of the heated up fuse will send the current down the other leg. The same holds true for a one amp fuse. All magically done with no user intervention.

I wasn't aware of that, but I'm sure my dual relay setup is operating as you indicate. When the original relay failed a few years I doubled up, installing them in parallel, and I've had zero issues since.

[patrickt]

Originally Posted by cycleguy55

I wasn't aware of that, but I'm sure my dual relay setup is operating as you indicate. When the original relay failed a few years I doubled up, installing them in parallel, and I've had zero issues since.

OK, it's not the classic method of designing a fail-over circuit, but wtf. Anything that is reliable for a few years on these cars deserves a chance to stay.

[cycleguy55]

Originally Posted by bkozlow

Generally, it is three words written on the relay "MADE IN CHINA" and if it is Bosch then your amp rating is to low. I would go to a German car dealer in your area and have the parts department find you a HD unit for one of their top model cars, more than likely they will be Bosch no matter what type car. Or you can contact Texas Industrial Supply at texasindustrialelectric.com/relays and look over their inventory. Look at 0332-002-168, if it were to fail then you have other problems in your system.

Bill K

Another option is pulling OEM relays from vehicles in a wrecking yard, er, auto recycling. This would be especially so if they have some German imports you can cannibalize for the necessary items.

I pulled 3 or 4 from a local U-pick and they didn't even charge me for them. With hundreds of cars in the yard and multiple relays per vehicle they don't even bother - especially when most people just pilfer them and don't ask. I guess they focus on things too big to pocket.