DEF has got me sitting at home now. I broke down Thursday and had to drop the trailer and bobtail back to the shop, got the springs and air bag fixed, left again Sunday. When I left Carter Lumber in New Castle to go pick up a load in McKees Rocks Monday morning the red "low DEF" light came on in the DEF gauge-but the gauge still showed almost 3/4 full, which was right. I stuck a piece of wire in the tank to make sure it had fluid in it, which it did, and all that accomplished was losing the top off the tank. Apparently I didn't get it back on there right, so I had to cover it with duct tape. Then after a while the check engine light came on and it derated itself, but it was still going. And using the DEF, because I filled it to the top at the Pilot, which didn't help either, and I could see the gauge moving. Then I stopped at the Mack/KW dealer in Jane Lew and got a new breaker and put it in, which didn't help either. Then I stopped at the Go-Mart in Nettie and got 2 slices of pizza, a drink, and a pack of smokes-that didn't help it either. In fact, it made it worse. When I started to leave the engine with the red circle around it lit up on the dash. Couldn't get over 4mph. after that, even when I dropped the trailer again and tried to bobtail- 4mph, tops. So I spent 18 hours on the side of the road in Levaisy, West Virginia waiting for a wrecker. We don't have any spare trucks now, so I had to wait until unit 21 got in, he runs to Baltimore and back every night, and they sent me that truck to get the load back to Lynchburg.