Adding a manual fan switch??

[snailexpress]

(02-15-2017 )JMBT Wrote:  I did a little more digging about doing this mod on a Volvo with a cummins motor. Here is what I found in the VECU and BBM manual on Volvo's website, in reference to connecting a 12V+, switched lead to the PA19 terminal.

"When used for a Volvo engine, the manual fan input must be connected as shown above. When used with a Cummins engine, there are two choices:

• Wire to the VECU as outlined above. However, the multiplexing setup in the ECM must be such that the “fan accessory switch” is enabled. The general “fan fea- tures” setup should be disabled.

• Wire to the ECM. In this case the manual fan must be enabled in the general “fan features” setup, and the wiring to the ECM must use a Normally Closed (N.C.) switch to ground instead of the N.O. switch to +V shown above for the VECU connector."

I can change the multiplexing setup of my ECM with Insite, to enable a fan switch through J1939, but when I do this I have to pick an address "source" that the command will come from, from a drop down menu. There are about 200 choices, none say VECU. So I am trying to figure that out next....
My other options are wire into pin #25 on the OEM, ECM harness, or add the second soleniod like Rawze mentioned above...

Don't worry about multiplexing. Switch is analog input, VECU will form the J1939 message to ECM with it address same as it does for fan on for engine break.
All settings you need.