pete 384 windshield washer motor

I have a 12 peterbilt 384 that the windshield washer motor doesn't work. The plug for the motor has good 12 volts when motor is unplugged. However it loses voltage under load when hooked back up to the motor. Washer fluid motor runs fine when tested with a battery on bench. I have checked ground multiple ways and determined it to be fine. I have replaced both relays that have to do with wipers behind the dash, however can't find a wiring diagram to determine if these have anything to do with the actual windshield washer motor. Fuses are all fine, I feel like their must be a relay somewhere that I am losing amperage through under load that goes to the washer motor. Any help would be appreciated thanks.

 

Yes it is mounted on the radiator.

 

1XP-VDP9X-9-CD141261 is vin, email toppingben@gmail.com
I appreciate the help.