No Tach instructions have helped me

:screwy: Im trying to put a Sunpro tach in my 00 dodge neon, and everythings all hooker up, the only problem is that the RPMs are about half of what they should be. I checked their website, and they didnt say that i needed an adapter, but I dont know what else to do.

The tach wire from the tach is connected to 1 of the 3 wires coming from the 1 cluster from my distributor cap. Ive tried all three wires.

If anyone can help, thatd be great. :screwy:

there is a switch on the back has setting for 4, 6, 8 cylinders. if it is set on eight it would make sense that it would divide your signal in half.

there is a switch on the back has setting for 4, 6, 8 cylinders. if it is set on eight it would make sense that it would divide your signal in half.

sorry i forgot to mention, Ive tried all three settings, and my Idle RPM goes from about 200 on 8, to maybe 500 on 4. thanks though

try the neon forums there smart one..

I agree with crj, though it could have been worded a bit friendlier...

I have an Autometer tach that I had to send back to the factory to have it adjusted for my 95 Neon. When I first hooked it up it only read 1/2 of the rpms.

the reason that the tach u bought isnt working is because there is no tach wire for a your neon if its anything like my 2001 neon, i tried to hook mine up yesterday and it did the same thing what u have it hooked up to now is the fuel injector wire so that is what its reading currently

I Think I Know why the tachometers only read half of the real RPM. The aftermrket tach was probably designed for a car with a distributor. In that case there would be 4 ignition 'pulses' to count per each two revolutions of a 4 cylinder engine. But the coil pack on the Neon is really two separate coils in one unit. And each coil is only fired 2 times per each two revolutions of the engine. It might be possible to connect Both of the 'signal' or 'trigger' wires going to the coil pack to the tachometer input: BUT, there would Have-To-Be a diode included in each wire - in series- to isolate the two halves of the coil pack. The diodes would let the tachometer see both pulses from both coils, thus four ignition pulses; without fouling up the signals from the PCM. (or destroying it)
Most diodes will have a painted band around the 'cathode' end. This is the side that I would run to the tachometer. The 'anode' end would be connected to the wire running to the coil pack. (If the tach didnt show anything I would reverse them.) Two 1 amp diodes would be good enough, but I would use diodes that had at least a 400 volt PIV rating: Because there would probably be a good sized inductive 'spike' on the wire to the coil pack.
For my Neon I bought via ebay.com a replacement instrument cluster with a tachometer in it. The wiring for that tach was already in the harness for my Neon - a 1997.

i dont think my instrument panal has a tach wire in its harness because i tested every connection with a multi-meter and had no luck finding a connection that was anything like a tach. But thanks for all ur input i am going to try and do this when i get home from vacation. i want it to work but then again id like to go to the autozone guy who sold me the tach and rub it in his face i was right and he was wrong lol