Gauges are incorrect and come on and off.

[stomis]

So I picked up an 86 Olds 442 yesterday. The speedo is dead on and the gas gauge works well. The temp sensor is jittery and comes on and off when I hit bumps. That I know has a bad connector or a rusted lead on the sensor, something simple.

The two things that really got me stumped are the tach and the volt gauge. The volt gauge reads something like 11-12v when running but the car stays charged fine. I havent actually looked at anything yet but I can tell its wrong.

The tach seems like its way off. It says I'm cruising at 3300rpms at 70mph with stock size tires. I know it should be right around 2200 rpms and the motor definitely doesnt sound like its spinning that much. Any suggestions on where I should start diagnosing this? I'm definitely thinking theres a bad ground someone.

 

[86Olds442]

So I picked up an 86 Olds 442 yesterday. The speedo is dead on and the gas gauge works well. The temp sensor is jittery and comes on and off when I hit bumps. That I know has a bad connector or a rusted lead on the sensor, something simple.

The two things that really got me stumped are the tach and the volt gauge. The volt gauge reads something like 11-12v when running but the car stays charged fine. I havent actually looked at anything yet but I can tell its wrong.

The tach seems like its way off. It says I'm cruising at 3300rpms at 70mph with stock size tires. I know it should be right around 2200 rpms and the motor definitely doesnt sound like its spinning that much. Any suggestions on where I should start diagnosing this? I'm definitely thinking theres a bad ground someone.

My guesses are:

Volt gauge - bad ground to cluster or gauge. Pull out cluster and tighten all connections there.

Tach - there is a 'switch' or 'pin' that is behind the tach to switch from v6 to v8. Those like to get loose or corrode and give bad tach readings. One the gauges are out you'll see it, it's orange, and clean it and tighten it up, or solder it.

That should fix you up fine. Good luck!

 

[stomis]

So I picked up an 86 Olds 442 yesterday. The speedo is dead on and the gas gauge works well. The temp sensor is jittery and comes on and off when I hit bumps. That I know has a bad connector or a rusted lead on the sensor, something simple.

The two things that really got me stumped are the tach and the volt gauge. The volt gauge reads something like 11-12v when running but the car stays charged fine. I havent actually looked at anything yet but I can tell its wrong.

The tach seems like its way off. It says I'm cruising at 3300rpms at 70mph with stock size tires. I know it should be right around 2200 rpms and the motor definitely doesnt sound like its spinning that much. Any suggestions on where I should start diagnosing this? I'm definitely thinking theres a bad ground someone.

My guesses are:

Volt gauge - bad ground to cluster or gauge. Pull out cluster and tighten all connections there.

Tach - there is a 'switch' or 'pin' that is behind the tach to switch from v6 to v8. Those like to get loose or corrode and give bad tach readings. One the gauges are out you'll see it, it's orange, and clean it and tighten it up, or solder it.

That should fix you up fine. Good luck!

Alright thanks man. I gotta pull the cluster to replace some bulbs anyway.

Do I need to pull the top dash pad to pull the cluster out? I mean I'll figure it out but its always nice to go in with a half an idea of how it comes apart

 

[86Olds442]

So I picked up an 86 Olds 442 yesterday. The speedo is dead on and the gas gauge works well. The temp sensor is jittery and comes on and off when I hit bumps. That I know has a bad connector or a rusted lead on the sensor, something simple.

The two things that really got me stumped are the tach and the volt gauge. The volt gauge reads something like 11-12v when running but the car stays charged fine. I havent actually looked at anything yet but I can tell its wrong.

The tach seems like its way off. It says I'm cruising at 3300rpms at 70mph with stock size tires. I know it should be right around 2200 rpms and the motor definitely doesnt sound like its spinning that much. Any suggestions on where I should start diagnosing this? I'm definitely thinking theres a bad ground someone.

My guesses are:

Volt gauge - bad ground to cluster or gauge. Pull out cluster and tighten all connections there.

Tach - there is a 'switch' or 'pin' that is behind the tach to switch from v6 to v8. Those like to get loose or corrode and give bad tach readings. One the gauges are out you'll see it, it's orange, and clean it and tighten it up, or solder it.

That should fix you up fine. Good luck!

Alright thanks man. I gotta pull the cluster to replace some bulbs anyway.

Do I need to pull the top dash pad to pull the cluster out? I mean I'll figure it out but its always nice to go in with a half an idea of how it comes apart

Yes, pop off the trim by around the light switch, and the two middle air vents. A total of 7 7mm screws hold the top dash pad, from there its 4 screws around the gauge cluster. Unscrew those, give it a tug, unclip the speedo cable and pull it out as far as you can until the cruise control wiring holds you back. You can either unscrew that sensor from the back of the speedo head, or work on the cluster in the car. I've done both. All in all, very easy and quick. Good luck!

 

[81cutlass]

Kinda on topic here,

My ralley pack voltmeter only shows 11 volts when the AC is off and the car has ran for a while. Thats when I have a true 13.5 or so. When the AC is on and town driving it shows like 8 volts, when in reality I have 12.5 or so. (I need a new altenator but thats another topic) Would that be loose screws in the back of the cluster? My tach also wont go past 3K RPM, I assume thats related to the low voltage in the cluster?

I might end up trying to solder the jumper lead instead of the little clip.

 

[85ss808]

Does this tach fix work for other g's like say my MCSS? I have a similar issue in that the tach is not accurate. All of a sudden, it reads completely off like above 1000rpm at idle and when I hammer it, it doesn't go thru full range- stops moving at 4500rpm ish. Also, my factory temp gauge is inaccurate with a brand new sender installed. Both of these issues occurred after installing my new engine ( which made its first start up kinda hairy). Anybody got any ideas? I plan on taking the cluster apart anyway, since my speedo cable is broken and needs replaced- just wondering if there is anything obvious to look for or try as a fix while I'm in there....