Tachometer not working please help.

I have a 2004 trailblazer v6 with 40k,  I just noticed that the tachometer is not working.  The car does seem to hesitate at times happens about 2 to 3 times per day.   I'm thinking its a sensor of some sort, checked it with my obd tester and I am not getting any codes.  Wondering if anyone has any idea as to what this could be.  Thanks alot. 

Check out the post I left about the speedometer on this forum for trailblazers, they said they were seeing tachometer and speedometer problems on these vehicles. Hope this helps.

I had the same problem with mine, at first the needle kept sticking so it looked like I was taching at 8000. Then it stopped moving all together.  Lucky enough, mine was still under warr. when it happend.  They had to replace the cluster asy.

Just like everyone else has stated your going to need a new cluster. Most gm dealers can get you a exchange cluster for half the price of a new one. They will have to install it due to the fact it needs to be programed.

I had the same problem, but it was coupled with the check engine light coming on. I took it in to the repair shop and they told me the light was due to the fan clutch being close to "going out". I replaced the fan clutch myself for about 1300 dollars less than the $1600 they quoted me. The fan clutch cost about $200.

Anyway, the rpm (tach) gauge was sticking too. It would eventually work its way back to zero and work fine for a few days all the while jerking its way up and down the gauge until it would freeze on the gauge somewhere between 5 and the letters RPM.

After I replaced the fan clutch the light was still on. So I took it to the nearest Autozone and they ran a code check (read) and said the cooling fan module was out. I replaced that at around $50 and the light went off.

I was told the instrument panel would have to be replaced to fix the RPM problem, but it's been 4 weeks since I fixed/replaced the cooling fan clutch and the RPM is working fine. Before it would only work a few days at a time. Just a thought. Hope it helps.

by the way....all the other gauges worked fine, just the RPM was acting up.