RPM Gauge eratic

[mia248vista]

2003 Volvo Penta 5.0 Gxi-B DPs

Gauge does not fall down to 0 when engine is off, sticks around 600 or so RPMs. When I start or increase the RPMs on the engine the gauge shows an increase as well but it is still off.

Mechanic without looking at it states it is the gauge but I get the feeling he just wants to sell me one?

What do you experts think/suggest?

Thanks!

 

[Don S]

Re: RPM Gauge eratic

Loosen the mounting bolts and see if it frees up. If not cycle the adjustment screw that sets 4,6,and 8 cylinders back and forth and see if it clears up. Make sure the connections are good, on engine and tach. If all is ok, you need a tach.

 

[mia248vista]

Re: RPM Gauge eratic

Thank you Don. On the engine side where does the connection terminate?

 

[Don S]

Re: RPM Gauge eratic

Gray wire on one of the coil connections.

 

[Jeepster04]

Re: RPM Gauge eratic

Is it normal for the RPM gauges to stick like that when the engines are off don?

Both of our gauges stay around 1k when the engines are off but work fine other wise.

 

[a70eliminator]

Re: RPM Gauge eratic

Most if not all the tachs I've messed with have a zero adjustment either a tiny little screw or small slide lever on the rear of the tach housing,though calling it a zero adjustment mignt not be the right term because it's more important to adjust the needle to read correct RPM's via a good shop tach, who cares where it zeros when the engine is not running, if it's way off then more than likely it's been jared and vibrated to the end of it's lifespan.

 

[slasmith1]

Re: RPM Gauge eratic

Is it normal for the RPM gauges to stick like that when the engines are off don?

Both of our gauges stay around 1k when the engines are off but work fine other wise.

Mine both "stick" on the last rpm of the motor when the key was turned off. If I turn on the keys without starting the motors they drop back to zero.

 

[sschefer]

Re: RPM Gauge eratic

There is nothing wrong with a Tach that shows 600 rpms with the ignition off. There is something wrong if you turn on the key and it doesn't go to zero.
The later would indicate either a faulty Tach or as was mentioned before, the mounting bracket has been overtightend and the needle is being pulled back against the face. I had a fuel gauge do that to me once.

Most marine tachs never zero because they lack a true ground.

 

[mia248vista]

Re: RPM Gauge eratic

Thanks for all the replies....

Turns out a faulty tach. I replaced it and working as it should.

Thanks!