tjnky

...when going up a hill my fan stops until I top the hill and it comes back on full force. Does it with ac on or just on vent. I am cornfuzzled. Ideas? Thoughts? Synde remarks?

freegdr

you mean the blower motor,buy a vacuum check valve and install it on the vacuum supply line to the vacuum ball

peep

You can always count me in for a snyde remark!
XJ fans are connected to a mercury switch positioned for sensitivity to front end elevation. As the XJ is so adept to be the consumate climber; the combined effect of also running the fan has found many an early XJ aloft some 20' or more at the summit of a simple climb. With Cherokees having both the mechanical and electric fan systems they behave as a juiced up heli propeller. As a safety precaution the fans are now auto-switch controlled for Cherokee uphill jaunts, just to keep the wheels in some favourable relationship with the ground.
Lifts and larger tires (they act like large balloons) also aggrevate the problem.
You could forgo these safety precautions and check out the clutch mechanism on your rad fan and the motor brushes may be failing on your blower motor and excessive rotor shaft endplay is disengaging the armature contact. Could be you are loosing vac signal to the dash fan controls and you fan is running althouh the air is being redirected (say to the feet)?
Just remember to buckle up for safety and stow all extra luggage in the overhead container prior to XJ uplifts.

tjnky

Yeah I am talking blower motor. The check valve, why would it need it? Not doubting you a bit, just wanna know the why it needs it.

tjnky

Just find it odd that it drops out on an incline only. Im not tracking with what's going on.

freegdr

you engine only creates vacuum at idle when riding it draws air in thru the throttle body ,thats why there is a vacuum storage ball to hold the vacum actuators open for ac when going up hill the vacuum is being sucked back thru the ball allowing the vents to shift to defrost theres a check valve in the ball to keep this from happening it gone bad no 6 in this diag

tjnky

Thank you kind sir. Another trip to the parts house. Its like Cheers...you know, where everybody knows your name. 11ty trips a week to Napa

freegdr

it will look similar to this