i have a b series swap in ek and my rpms dont read on my cluster unless the clip on the wiring harness that goes to th altenator is partially unplluged. (not fully pushed into the altenator). i may b wrong but dosent the rpm signal come from the dizzy? i dont understand why the altenator plug would make a difference unless the wiring runs through there for some reason. any help is appreciated. thanks

 

What year? 96-98 or 99-00? The former get the tach signal from the ICM whereas the latter get it from the ECU.

 

its a 2000 civic. my tach worked before i did my swap and i used my original wiring harness from my d series motor

 

None of the wires in the alternator plug directly affects the tach signal. If the alternator connector is plug in all the way, does the alternator work (i.e., charge the battery)?

 

ya. everything works properly while plugged all of the way in except the tach.when it is partially unplugged it sputters a little bit but the tach works.

 

Could be a loose wire on the tach.

 

Could be that when you plug the wiring into the alternator you are pulling the wire harness in such a way as to affect the wiring to the ECU or some other part of the car. Basically, you could be unplugging/affecting some other part of the harness by stretching the harness to plug in to the alternator.

Since it is a swap the engine harness may be a little "small" or "short."

There was this scientist named Occam...he use to say, "Entities should not be multiplied unnecessarily." That means that the simplest answer is nearly always the right one. So, check the rest of your harness and all the other plugs to make sure that you are not pulling out one plug by plugging in another.
They call that "Occam's Razor" since it cuts out all the crap!

 

well the wires are not stretched at all,there is plenty of slack...is there any way to test an altenator with a volt meter?

 

What ECU? If its an OBD1 or OBD2A ECU you wont have a tach unless you wire in the tach signal wire from the distributor to the cluster (or alternatively from the distributor to the tach test wire.

 

That's not true. I replaced the stock cluster on a 92 civic (OBD1) and the tach was working fine. I didn't have to add any wiring; it's pre-wired. I'm guessing it's the same for at least some OBD2a cars.

Also, he said his tach is working intermittently so again, I don't think he needs to run any new wires.

 

You misunderstood, '99 - '00 civics get their tach signal from the stock ECU, or another OBD2B ECU, however if you use an OBD2A or OBD1 ECU you wont have a tach signal unless you run a wire from the igniter in the distributor back to either the tach test wire in the engine bay, or to the cluster, doesn't matter which location you choose, either works fine. All '88 - '00 civics are prewired for a tach, this isn't the same.

 

im runnin a obd1 p75 ecu. but it has to be gettin some sort of signal to work if i pull the altenator plug out a little bit.where do i find the tach test wire so i can give it a try?