Choosing correct COdE value for VDO tachometer after alternator replacement

[JonasE]

I have replaced my original alternator on my Volvo Penta MD2040 with a Balmar 120A alternator and a serpentine belt conversion kit.

After the installing the new alternator the tachometer shows incorrect values. After googling a bit a found some manuals of other CDO tachometers where you could set the correct Pulse value. Replaced the broken display for the hour meter on the tachometer today and was planning to set the correct Pulse value. Replacing the hour meter display was fairly easy once the display was delivered.

In all the manuals I find from other VDO tachometers you are supposed to hold down the bottom while turning on the ignition until PuLSE is displayed and then enter the correct Pulse value.

But when I hold down the bottom on the tachometer when turning on the ignition there is only CoDE displaying where you are supposed to set some specific Cd value.

Where do I find what Cd value to enter for my alternator?


- The new alternator is a 12 pole alternator with a 1:2.166 ratio (Pulse = 12 x 2.166 = 25.992)
- The tachometer is labeled with both a VDO and a VolvoPenta part number.
VDO: N 02 070 109
VP: 873588
- The engine is a Volvo Penta MD2040-D

The current Cd value on the attachment is just me fiddling around and not something that is correct....a tachometer for my VolvoPenta MD2040

 

[Keith-i]

Post 16 onwards here http://www.ybw.com/forums/showthread.php?203811-Tacho-Reading-high-by-50/page2 might be of interest to you.

 

[JonasE]

Thanks Keith-i have seen that post. I do have a similar tachometer and my old alternator was similar to the one in that post.

In my case I know the ratio and the number of poles. But instead of finetuning I would like to start out using the correct "Code" before fine tuning. That I why I am searching and trying to find information about the meaning of the different "Codes" in the settings of the VP alternator.

The ”SELECt”, ”PuLSE” and ”AdJuSt” options on newer VDO tachometers are not available on this tachometer. The only option to set the calibration other then fine tuning is using a ”COdE”.

 

[rszemeti]

Ignore all that stuff about ratios and poles. As well as the number of poles, there is the pulley ratio between the engine and alternator, which can vary with belt wear. Simply buy a laser tacho from eBay, for £7.49 and measure the actual RPM of your engine and then try all the various settign options until you find one that matches the reading on the VDO Tacho to the actual RPM ...

 

[JonasE]

Ended up testing different Code values and found Code 7 to be closest. Could aslo easily fine-tune the tachometer using a tachometer app on the phone and a piece of white tape on the engine. Fairly easy once I got started.