I have 2000 Yukon XL front heater would only work on high and now now no speed?

SOURCE: 2005 Yukon XL Denali: Heater

Does it work on any speeds? If it still works on high then the blower resistor is bad. On the passenger side under the glovebox is the blower motor and resistor.If possible try wiggling the pigtail plugs that attach to these two components.It is not uncommon to have problems with these pigtails.Also try tapping the bottom of the blower motor to see if it will start working again.If it does The connections are poor and need repaired. If the blower will not work at all check for power at the blower motor pigtail with a test light or dvm. Will be glad to assist further if more assistance is needed.

SOURCE: The Heater fan in my 2003 GMC Yukon XL will not turn off

I don't know if you already fixed it, but I had the same problem on my 03 yukon, TysonRicky is right. In my case it was the blower control module. You can find it right under the glovebox. It cost me close to $100 for a new one, but very easy to replace. Can't even imagine how much it would've cost me if I had a mechanic do it.

SOURCE: 2002 Yukon XL with Delco Stereo only has front

sound like the head unit's out put mosfet is going bad, but i have also ran in to this problem when it was a speaker wires shorting out. so first check the connection on your rear speakers.

SOURCE: 02 GMC Denali front heated seats won't work

test to see if you have any power going through all the connectors for the seat heater, there may be a spot where there is a connector that has gone bad, or potentially it could be the whole element that is bad