If that makes any sense.... The fan is barely pushing air in first three positions then rages in high. No gradual increments on 1-2-3-4. Any clue? This is a new to me 99 xj and is all or nothing fan wise. Previous owner said heater core was new if that helps. Thanks for help search turned up less than the correct answer.

If you are moving down the road when checking low blower speeds, it may be just ram air coming in, and the motor isn't running at all on low speeds (??) Maybe a check of the blower resistor would worth doing, or maybe even the switch.

I just went through this, The switch connector was fried, the resistor thermal fuse was open etc. Had to replace those & the blower motor, which was drawing too much amperage. What year is your Jeep ?

It's a 1999. Mmm will check in the am. Could just be ram air. I'll rip into it and see. Just looking for direction I guess thanks!

I just bought a 99 2WD today that has this exact problem. Where you able to fix?

Not sure about a '99, but on my '94, there is a plastic cover under the dash on the passenger side, held on with 2 screws. The cover has the blower motor resistor under it ( above it actually ! ) along with a heater door actuator, (called a motor in the manual)
That resistor is what slows the blower fan motor for the lower speeds. You can buy the resistor locally ($) or buy one online like I did.
And the blower switch in the dash may need replacing also. Mine was a bit fried, as well as the connector for it.

The blower itself may need to be replaced also, if it's drawing too much current and taking out the resistor etc.

Hope this helps.....

Bill

Thanks i havent had a chance to get in there yet but id bet thats the solution steelybill. Tobtech i didnt attempt the fix yet. No days off til early dec but soon i ll get goinq! Thanks for the help steely!

I will dig into mine this week and post the results. It looks like the blower resistors are pretty cheap.