Gen3 02 Silverado Fan Conversion Issue

[cwkreska]

Hi everybody!!
I have a 2002 Silverado, 5.3T, 4L60E 4wd. I just upgraded to a 130amp alternator and added electric fans. Flashed the new settings to the ECM and couldn't figure why it wasn't responding properly, with the fans running as they should. I just manually turned on the fans and realized they are pushing instead of pulling. Does anybody know if there is a way to reverse them or are they generally one direction only? Dual fans for a 2006 Sierra, 34" radiator, aftermarket wire harness using triple relays, dual fuses, white to C1-42, Green to C2-33(removed existing recirc wire).

[SiriusC1024]

Reverse polarity of the fan wires.

[cwkreska]

Thanks. I read one post that said don't because it makes the fans last a shorter time and another that said they are supposed to be reversed as the harness is wired for 12v+ but on the truck they use 12-(make a ground connection to turn on). Working great now!!

[blindsquirrel]

Polarity of the control side of the relays has nothing to do with polarity/direction at the output side to the fan motors. If you had a module that supplied a positive trigger to turn the relay on, you'd give the other pin of the pull-in windings a constant ground. The load side/output of the relay just works like a switch, but one that's remote controlled with an electrical signal instead of a lever you have to pull.

A brushed DC motor's direction reverses if you reverse the polarity. Totally separate thing from the type of signal used to trigger the relay.

[SiriusC1024]

Right, so giving it power or giving it ground is going to be handled relay-side. If fan life is reduced one vs the other it's because of voltage drop. The fan motors will draw the same amount of power either way. When voltage drops, current increases, resulting in more ohmic losses (heat).

Basically, as long as you're matching the factory wiring diagram then rotation is handled with fan wire polarity.

[SiriusC1024]

And since squirrel mentioned brushes that made me remember. This is another factor where polarity matters. A couple other examples is the difference in penetration DCEN vs DCEP if you're familiar with welding. Or, the wear of the contact pads of a starter solenoid if you've had one apart. It all has to do with the magnetic field of the plasma arc, but that's irrelevant. Point is get the polarity right.

But again, if the factory wiring diagram is used, then correct fan rotation automatically means correct polarity at the brushes.

[blindsquirrel]

Some brushed motors have an... not an offset exactly, but brushes that are not perpendicular to the armature. Those prefer one direction over the other but still go either direction depending on polarity. Sometimes you can run into longevity issues if you have one that's designed to be a puller, but you ignore the instructions and use it as a pusher and swap polarity to make it move air the right direction. If it's a factory fan motor with the correct factory blade mounted in the factory location and it spins the wrong way, you wired it backwards (at the fan connector, not at the relay).

[SiriusC1024]

Damn this is one of those times I'm really impressed. Who would even know that the brushes are offset? Most people just change the motors out and throw them in the trash. I feel like you've carefully dissected every piece of every GM platform made since like '91 lol.

I can see how that offset would wear the brushes through friction if the rotation was backwards.

[blindsquirrel]

Nah, aftermarket fans are like that too. Some are advertized specifically as 'reversible', and that's only partly down to the blade design, it's different in the motor too (straight brushes so it doesn't favor one direction over the other). A non-reversible motor lasts (somewhat) longer as long as it's turning the right direction.

[cwkreska]

I will end it with this....Now that the fans are pulling instead of pushing, they are much quieter and work more efficiently. Watching the volts gauge, I would definitely recommend you upgrade to either the 130 amp or 145 amp alternator. I programmed just as several have posted and my a/c fan runs when the a/c is on, only goes on high when the water temp reaches the set value. Engine fan comes on at 190 and off at 180(may reduce those). Thanks again for the training and help!