fan is good am happy with it because am living at gulf area very hot area, and its hard to find a good electriciton, now my plan to connect two relay may that reduce the pressure of the relay. i hope that
The JK uses a single wound fan, but wanted two speeds; so...
They added a voltage divider(fan resistor) to step the voltage down to about 8V for a low speed operation, this is important.
A true dual wound fan or variable speed fan would have been a better, but more costly, solution.
First the voltage divider can handle only so much current, the stock fan runs at about 20 amps current draw. The problem is with start up, to turn on the fan from off to low will introduce a inductive kick of about 40-50 amps. To go from off directly to high can bring that kick to near 100 amps damaging the circuit and relays. There are two relays, low speed is in the TIPM and high speed is behind driver headlight.
So if you are running only one speed we can assume it is high. On top of that you say the fan motor has been changed out to a more powerful one? So you are going from off to high running more current through the circuit than it is rated or designed for.
The solution is to stage the fan from OFF - LOW - HIGH to protect the circuit and components.
If you have a high current fan please ditch the voltage divider and install a HD 50 amp relay directly off the battery. Get a dual wound fan so you can power it up on low speed then shift into high which will keep the electronics happy.
Actually we are going to offer a similar set up for JK's that require extra cooling. The fan we are using is near 5,000 cfm and will melt the stock electronics.
Just adding a larger fan and not upgrading the electronics will cause problems. We will offer a HD relays that are properly stagged, heavy gauge wires and a true dual wound fan motor that will have a failsafe mode if one winding fails.
As a side note we took a hard look at the Pentstar fan to upgrade earlier JK's, it is powerful. Besides costing near $400 for the fan module we found the circuit driving the fan is not a true PWM, it is an odd step modulation that is difficult to control. When we discovered Chrysler is having issues with fan control we decided to keep it simple and stay with what works. We have been using high CFM variable speed and dual speed Lincoln fans for years in our swaps with no issues, they can pull nearly double that of a stock JK single wound fan, and with the proper wiring and relays will last a long time. The set up will be triggered by the stock JK electronics so the fan will remain computer controlled for engine temp and condenser pressure.