I have a 1999 XJ sport an the ac blower stopped on day with out warning. It will not work at any speed. I tapped on the blower motor from under the hood and it did run on low with the control on High for a little while. Now nothing. Any body have any ideas on what it could be. Thanks

 

There are a few components that could be causing your issue. There is a relay, and a resistor behind/under your glove box (you'll need to remove the glove box and some trim to get to them). I have also seen some posts about the wiring for the climate control being bad and melting.

I fought mine a few years back, and it ended up being the blower motor that was bad. My issue was at times the blower motor would not work. Then it would suddenly start working again, and would sometimes work for days before acting up again. Made troubleshooting difficult.

 

Well I did bump the blower motor and it started running on low then it stopped the next time I started the car.

 

That could be any of the reasons jpz gave. I'd say it's most likely the blower motor, but some troubleshooting is in order before you go buying parts. It's probably not the relay, but those are easy to check or replace. so start there. Then the switch.

 

Remove the blower motor and bench test. As they get older they pull more amps creating heat. Also, check wiring for burned connections.

 

This is what I ultimately ended up doing. I really struggled troubleshooting mine, because it was so intermittent. My problem would go away for days, or sometimes weeks making me think I was onto a solution. I ended up pulling the motor, and comparing resistance readings on the new motor vs old motor. Old motor has much higher resistance readings, and was actually harder to turn by hand. After I replaced the motor all my issues went away.

The only issue is the motor is not the easiest thing to replace, so I wouldn't start there. I would pull your relay, and resistor and see if there is anything obvious there. Pull the control panel, and look for any obvious problems there too.

 

Exactly. Even though the blower motor is probably the culprit, it's a very large job to remove it. So, start with the easy stuff and rule that out first.