98GMC 1500, been having some trouble with my ABS light and my Heater Control, whenever the abs light comes on the heater control shuts down. Took it to the dealer for a scan, and both front wheel sensors are bad, and they had no idea why it would shut down the heater/AC. Anyone ever heard of a problem like this? I there something i can check for at home before letting the dealer charge me to figure it out?