Lude Generation

Hi Guys,

I hope you're all well.

I have a very odd issue on my 4th Gen. My H22 manual (converted from a H23 auto) has got an issue where its not charging the battery. I am getting about 11/12.5v whereas I should be getting at least 14/14.5v.

What I have tried:

- Brand new battery, then a used one from a working Prelude.
- Replaced the alternator from a working 2 x Preludes (tested it before removal and both were giving 14.5v)
- Check engine fuse box, no fuse was found blown.
- Replaced engine fuse box.
- Checked voltage coming from alternator plug; white/green, white/blue and black/yellow. Nothing from white/red) I think that's normal?
- Checked fuse under dash, all OK nothing blown.
- Replace Fuel Main Relay.
- Checked all earths in the engine bay (most of thing at least).

Is there anything I've missed? Any suggestions would be greatly appreciated. I am puzzled!

Thanks,
Arif

Have you checked the battery? Might have a dead cell inside

ek9sid wrote: ↑

Sun Oct 31, 2021 7:08 am

Have you checked the battery? Might have a dead cell inside

Hi @ek9sid

Yes, I forgot to mention I fitted a brand new battery too. And after that to be sure, another one from a working Prelude.

Have you checked the voltage output from the large black wire from the alternator along its entire path.

Check it at the alt output, then at the other end where it goes into the fuse box, then where it comes out of the fuse box to the battery.

Vtecmec wrote: ↑

Sun Oct 31, 2021 8:49 am

Have you checked the voltage output from the large black wire from the alternator along its entire path.

Check it at the alt output, then at the other end where it goes into the fuse box, then where it comes out of the fuse box to the battery.

Hi @Vtecmec

I’m sure I remember checking it. And it was about 11.5-6v and the same coming out of the fuse box too.

The car is in my parents garage so ill pop back and double check but I’m sure it’s what I was getting.

Is that what it should be giving me?

As Vtecmec says, check output at the alternator you need to disconnect the large battery cable and then test the alternator to see if it's generating 14v if not check the exciter circuit is providing voltage to alternator in order to create the magnetic field required to generate electricity. If that's ok and the alternator isn't outputting then it's either the bushes or the rectifier. Very rare do the windings fail it's usually one or both of the latter.

Greg wrote: ↑

Sun Oct 31, 2021 9:36 am

As Vtecmec says, check output at the alternator you need to disconnect the large battery cable and then test the alternator to see if it's generating 14v if not check the exciter circuit is providing voltage to alternator in order to create the magnetic field required to generate electricity. If that's ok and the alternator isn't outputting then it's either the bushes or the rectifier. Very rare do the windings fail it's usually one or both of the latter.

Hi @Greg

The alternator has been tested on another prelude before removal and even after fitting back.

This is a bizarre issue. The car has been sat for about a year and a half since Matt @ Red- R Performance.

is there no warning lights on the dash? maybe try a battery booster when starting it up... and check the belt is tight..only issue ive ever had with alternator on a 4th gen ( in 20 years of running them daily) is when the crank pulley came loose but that threw up a warning light on the dash along with the engine cutting out

If the alternator works on another car and is otherwise without fault it can only be continuity between either the battery and the alternator or the exciter circuit and the alternator. There isn't much else technically to it, the charging circuit is pretty simple so if the alternator is definitely ok the problem must be the wiring as mentioned already

Wires itself should be fine. But you should check all connectors. What you can try is unplugging battery while engine is running. If it will stop than there is no connection between alternator and battery. Loose connections provide high resistance which will not affect multimeter as bad as when you draw higher current.