speedometer & a/c not working

[paigehb]

I have a 2004 GMC Sierra 1500 pickup and was driving home from work the other day and noticed the speedometer was way off. I was probably going about 30 mph in town and it was showing almost 90. The speedometer would not go back down to 0 when I turned off the ignition. So, we tried unhooking the battery for awhile and rehooking it up later. It did get the speedometer back down to 0. Worked a while the next day, but now is messed up again. Then today, I tried turning on the A/C and noticed a hot smell. Also, blowers on left hand driver's side would not blow out at all, and on right-hand side they were blowing out really cold air. When I was driving home today, started smelling a hot smell, so turned A/C completely off and smell went away. Still felt like some warm air was coming out down at the bottom. Any suggestions? I am assuming the two are related. No problems of any kind until now. Of course- after warranty is up. Thanks!

[kerrazy]

paigehb -

I have/had very similar issues to yours. I had to have my HVAC blower replaced because all at once my AC quit working. Cost me $140 to get it replaced. My controls quit working but it was still under factory warranty, I think they replaced a relay switch. Now my Speedometer stopped working, same scenario as yours: was working then on highway was reading 0 mph while driving at least 70. Would work for a bit then slowly drop off, shoot up to 120, now its just stuck at 10 mph and has not moved since.

[PK55Z85]

sounds like your gonna need a new cluster(speedometer) unit, you may have a problem with hvac control head assembly(part on dash with the buttons)
we been seeing quite a few of speedo-cluster problems.