Power Issue??????????

Whenever I put my wipers on with my defrosters on full blast, my wipers get very boggy. What is causing this?

We need a better more complete discription!
Could be a voltage problem if it's a older XJ or simply a dry windshield with no water to allow the wipers to move. Most likely the former. If the AC is hogging all the battery/alternator's power or causing the belt to slip then the voltage dropps and the wipers slow down. (the ac runs when you turn the defroster on if it's above a certain temperature)

JoBo

By mentioning 'defroster' I assume you mean the rear defroster??? At any rate, it may be that the system is just loaded down, defrosters have always been a high amp draw on the system, and so is the fan. By running the rear defroster, having the fan on mid to high speed, and the wipers going, you are putting a nice load on the system. You may cure this malady by purchasing and installing an alternator with a higher amp rating.