How hard is it to install a tachometer. My engine does not have and appears to have never had one. From what I've been reading it appears to be important to be able to monitor the engine rpms for diagnostic reasons. How does it connect and where does it get it's data from? I'm engine illiterate but learning.
Installing a Tachometer
- Thread starter Gary_H
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A typical diesel engine will provide a tach signal from the alternator. There should be a connection for this and it will be shown in the engine or alternator wiring diagram. The alternator connection is usually marked with a "W".
The only other connections that you need are +12V power and ground. These you would pick up from the engine control panel so that the tach is powered only when the engine is running. One last connection to the tach is the panel light connection and that you would also get from the engine control panel. Simply find the existing panel light connection to the other gauges an tap off of that connection.
To calibrate the tach to your engine it is helpful to know the number of poles in the alternator. This is usually either 12 or 14. The elecronic tachs that I am familar with are programmable. You would simply program via buttons on the back of the tach for the number of poles and the ratio of the engine and alternator pulley. You can then tweek the final reading to be accurate. It works best to have an optical tachmeter for this final adjustment.
I had to replace the tach in my Volvo panel a couple years ago and I found a suitable tach on eBay for $20. Works perfectly. I also bought a optical tach on eBay for about $25. It's useful not only for this project but also for checking lawn mower engines. lathes, and any other rotating machine speeds.
I have programming instructions for the VDO brand of tachs if that would be of help to you. Email me from the owner's directory if you need these.
The only other connections that you need are +12V power and ground. These you would pick up from the engine control panel so that the tach is powered only when the engine is running. One last connection to the tach is the panel light connection and that you would also get from the engine control panel. Simply find the existing panel light connection to the other gauges an tap off of that connection.
To calibrate the tach to your engine it is helpful to know the number of poles in the alternator. This is usually either 12 or 14. The elecronic tachs that I am familar with are programmable. You would simply program via buttons on the back of the tach for the number of poles and the ratio of the engine and alternator pulley. You can then tweek the final reading to be accurate. It works best to have an optical tachmeter for this final adjustment.
I had to replace the tach in my Volvo panel a couple years ago and I found a suitable tach on eBay for $20. Works perfectly. I also bought a optical tach on eBay for about $25. It's useful not only for this project but also for checking lawn mower engines. lathes, and any other rotating machine speeds.
I have programming instructions for the VDO brand of tachs if that would be of help to you. Email me from the owner's directory if you need these.
Your engine might not be equipped with the tach sending unit - ask the manufacturer. If not, you will have to have a wire soldered into your alternator by an alternator shop and use that to drive a Teleflex tach. You will have to do some research on your options here.
BTW - a tach is a helpful and useful addition to your instuments.
BTW - a tach is a helpful and useful addition to your instuments.
Most alternators don't have the tach connection "standard" - you may have to wire it in. Then, you can TRY calibrating the tach based on pulley ratios, etc. but you may or may not have an accurate measurement when you're done.
If it's for diagnostics, a hand tach is a much better idea. I have a mechanical one, but if you can get an optical hand tach for $20 on eBay, go for it! If you have both, you can use the hand tach to calibrate the panel one. It doesn't even have to read properly - you can just "remember" that 2000 on the tach is actually 2500 (or whatever) once you've determined that.
druid
If it's for diagnostics, a hand tach is a much better idea. I have a mechanical one, but if you can get an optical hand tach for $20 on eBay, go for it! If you have both, you can use the hand tach to calibrate the panel one. It doesn't even have to read properly - you can just "remember" that 2000 on the tach is actually 2500 (or whatever) once you've determined that.
druid
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