Troubleshooting Tachometer.... any ideas?

[NMShooter]

Installed a used tach for my 1988 85 hp force. 20p setting selected.

Did the install late at night after work, and managed to reverse polarity on the power to the gauge initially.

Corrected the power polarity.

Tried first test today. With ignition turned on, meter hits rail at 8000 and stays there. Stays at 8k even with motor running.

Purple tach wire shows about 6.7VAC, and also reads a DC component on my simple meter of about 7V.

Did I fry the gauge with reversing the power polarity? I'm going to be pissed if so. At both myself and Faria for not placing a $0.10 diode inline with the power regulator.

Any thoughts? I bought this gauge off of ebay and do not know if it was functional prior to install.

Thanks.

 

[NMShooter]

Re: Troubleshooting Tachometer.... any ideas?

A little extra data... I have pulled the gauge, and did a quick test that Faria has listed on their site. Applying 12V to the gauge without any signal input results in a reading of 8k.

Tying the signal input to ground and applying 12V also shows 8k rpms.

 

[NYBo]

Re: Troubleshooting Tachometer.... any ideas?

Looking at some of the documents on the Faria website leads me to believe this may be fixable by the owner, but I can't find the document they say has the fix. Try contacting them.

 

[NMShooter]

Re: Troubleshooting Tachometer.... any ideas?

Fixed!

Called Faria and was a bit frustrated by lack of customer support. The customer support guy said that he had no record of my gauge in his "system" and that it was probably an older gauge that they no longer even had service manuals or schematics available. I was pretty seriously in WTF? mode by the time I hung up, and of the mindset that there won't be any Faria gauges in my future based on their lack of support.

Out of desperation, I pulled the gauge apart. Had to bend the bezel cover off to get back in there, but when I pulled the circuit board out, I noticed a bad solder joint on the frequency to voltage converter. I resoldered the thing, put it back together, and voila.... it now seems to work just fine.

 

[NYBo]

Re: Troubleshooting Tachometer.... any ideas?

Nice!