So I noticed the other day that my RPM gauge is acting crazy. It will sometimes just sit at zero and do nothing, other times it jumps a thousand RPM's or more for no reason. It almost acts like the needle is sticking. Any thoughts on what could be causing this? All my fuses are fine BTW. Thanks.

 

Your alternator is going bad.
The alternator is what the rev counter gets it readings from.

If the tach is at zero the alternator is not charging the battery and your battery light should come on.

Go have your alternator tested.

 

LOL...Mine is doing the same thing at the guy at the parts store told me it was a bad crank sensor causing it. Thanks for the real answer, Spike!

 

Ditto


luck,greg

 

I fixed mine very easily! The serp belt on mine was going bad, so I replaced it this morning. Ta da! Tach works fine now. The belt must've been slipping on the alternator pulley causing the tach to sporadically work. So maybe you should have a look at your serp belt before you go pulling the alt?

 

Never listen to the $5.00 an hour parts guys. That is a pretty good example, a crank sensor failing causing the tack to not work well.

 

Thanks for the answers guys. The belt looks good. I noticed this for the first time the other day when temps here in North Texas hit high 80's low 90's so maybe the heat allowed the belt the stretch just enough to allow for slippage. The gauge is working normally as of today. What do ya'll think? I will pull the alt Sunday and have it bench tested at AutoZone. I will let ya'll know what I find.

 

No need to pull the alt out of the truck, just take the whole truck to Autozone and then can test it while in the truck.
Check all of your wires first though, a loose wire can cause this too.

With it acting up while hot means that the rectifier is going bad.
I just got back form TX and after my truck had been running for 15 hours all the heat build up caused my tach to jump around and my lights to flicker.

When I replaced my alt the alt was so hot you could not hold onto it.

 

Here is my thread.

https://landroverforums.com/forum/sh...ad.php?t=30730

 

mine did the same thing, the belt was routed wrong. I know your thinking theres no way my belt is on wrong but check it anyway, there are 2 ways it can go that seem right but it will not quite have enough tension. mine was wrong for months til it got cold and wasn't sticky enough to grab the pully.