Thread: Tacho

Originally Posted by 85 county

OK i got a 52mm tacho off ebay a while back

hooked it all up, good so far

but now im idling at 1500 rpm and 110klmh is off the clock 4000rpm

since there is no ajustment on the tacho is there any way to trick it?

Ah, you are using a tacho designed for an ignition system. Your tacho feed is coming from the alternator which produces many more pulses per engine revolution.

Possible solutions: a pulse count corrector, probably sold as an electronic speedo corrector, should be available from auto hot-up shops etc. or ebay, try this:

SUZUKI SPEEDO TUNER SPEEDOMETER CORRECTOR - eBay (item 110603402852 end time Mar-24-11 14:37:19 PDT)

Another possible solution, use a bicycle speedometer, set the magnet on a pulley somewhere. I saw an old Rolls Royce set up that way because the owner didn't want to open up the original gauges. It may take a bit of trial and error to enter the correct wheel size number to get a meaningful reading. Doubles as an hour meter!

I got a genuine Isuzu tacho from Zenith Engineering. This has a transducer that replaces one of the plugs under the body of the injection pump.

Hey all,
I recently purchased a VDO tachometer which runs off the alternator. Only problem is that I'm not sure how to connect it up. Any help would be greatly appreciated.

Thanks in advance

The unit that gets the reading from the alternator. You need to solder a wire to one of the out puts of the rectifier. Your alternator produces alternating current, the rectifier makes it direct current by taking power from three points of the alternating current. ( something like that ) The tacho counts the pulse. So you need to open up your alternator to solder this wire on. I was lucky with a Land cruiser one that I did. Was able to do key hole surgery though a space were the wires exit the alternator. Once you get this wire attached you need to get a potentiometer and take a reading of the revs from the crank pulley when the vehicle is at normal running temp. Hook you tacho up out side of the dash so you can adjust it. There should be some small adjustment devices on your tacho. On should be a choice of 4, 6, 8 cyl and a fine adjustment screw. Once it reads the same as the reading you took from the crank ( don`t make any engine adjustments between taking the crank reading and adjusting the tacho ) install and enjoy. I have also got one like this for my ute. But it seems that I might have a generator, so will have to get this confirmed. The best one for ease of instalment I have heard of is one that has some sort of band that goes around the alternator and detects the pulse. But can`t locate one.
Cheers Hall

Not sure if you have the instructions, and they are confusing - or if you dont have them at all. If you don't then this might help:

http://aftermarket.continental-corpo...eter_52_mm.pdf

Steve

These are the instructions I got with mine

This link also explains what and how of tachos and alternators

Thanks, however my alternator doesn't appear to have a W connection readily available and am not all that savy with alternators to make a connection so maybe worth while having an auto elect carry out the work