Re: heater only works on high
if youve actually been losing speed settings I'd suspect a faulty blower motor resistor assy over a relay. as far as where your relays are located you could possibly find out by checking the cover on the fuse/relay center under the hood and/or under the dash. also, a component locator manual, alot of aftermarket repair shops have these manuals for locating various components in vehicle systems and may help you out. ( you can find the blower resistor assy in these manuals as well) I hope this helps!