Hello. I recently did a jdm motor change on my 01 Honda civic lx. I put in a 1.7 vtec. Now I'm having alternator problems. I've gone through 3 now. I'm losing volt when coming to a stop. It drops down to 12.4. But when driving it goes back up to 14.2 or I can just leave on my head lights and the volts won't drop. I'm lost on this problem.

 

1. If this happened right after the engine swap, did you use a different ECM?

2. It may be an issue with the following (but not limited to):

• ELD, located in the under-hood fuse/relay box (ELD is separately replacement on your car).
• wiring
• ECM.

 

ELD at work.
As long as it holds a stable voltage with headlight on, and no flickering headlights, nothing to worry about.

 

I have changed out the ELD. I lose volts during the daytime and only when I come to a stop. But at night I don't lose anything volts when my lights are on.

 

It happened about a week after the motor swap.

 

Does the voltage hold stable when stopped like leok99 mentioned?

If it does hold stable when stopped and doesn't go any much lower, what you're seeing may just be the normal operation due to the ELD in conjunction with the ECM and alternator's voltage regulator. Honda uses it for fuel economy.

 

When driving the volts are at 14.2. When I start to slow down the volts will go down. When stopped the volts are at 12.4 and the battery light comes on. The minute I take off and the the RPM is above 2000 the light turns off and the volts go back up slowly. But if I leave my head lights on there is no voltage problems.

 

Okay, there is an issue since the charge indicator light (battery symbol) comes on.

This is a shot in the dark. Check that under-dash Fuse No. 4 (10A) is firmly in the slot in the under-dash fuse box. The fuse provides power (when ignition switch in ON or START) through the Blk/Yel wire at the alternator. It is use to energize the voltage regulator for the alternator to charge. Also check the connector at the alternator.

 

Ok thank you. I will check it out when I get home.

 

I check the 10 amp fuse and its in tight and good

 

Did you use the same crank pulley that came with the engine? It is possible the crank pulley is bad.

The crank pulley is a harmonic balancer and not a solid piece of metal. The inner and outer part part of the pulley is metal, while the middle is rubber. If the rubber separates from the metal, it will wobble and may cause issues with the belt tension on the alternator.

Take a close look at the harmonic balancer (crank pulley) with the car running.

 

I used my pully from my old motor. Its all metal. The pully came off 1.7 LX motor. The motor in there now is a 1.7 Vtec. But I'm not using the Vtec.

 

The crank pulley may look like all metal; but, usually the middle has rubber. Still, take a look at it with the engine running to see if anything unusual is going on.