[Heideisadog]

Okay so just finished my cars alt conversion. Everything is going great! All in and all good.
Though when I start the car it runs fine. As soon as I switch the head lights on though the revs start to go up and down. I have a video to add. Don't understand why it's happening. So if anyone can help please do!!

Here is the video, hope it showes what's happening.

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[Reubs]

It's obvious the idle up on the carby is dropping in and out. Do you have a multimeter to confirm you have a steady 12v at the plug for it's solenoid valve?

[Heideisadog]

Yeah, I don't, but I can get one. I'll try and get one tomorrow, where am I testing from sorry?

[coily96]

Just a temp fix until its sorted.
Look at the front of the carby when this is happening, you will see a lever moving back and forth.
Back this screw off so it cant make contact with the arm that runs through the carby.

[Heideisadog]

Yeah I was planning on doing that. Still need to find the cause.
I have been told it could be the voltage regulator. Anyone have experience with these?

[Reubs]

Time to get that multimeter - you should have have a steady 14.0-14.4V at the battery terminals if it is working correctly.

If you had alternator issues to the point that solenoid is dropping in and out then you'd be seeing that voltage drop cause issues with everything electrical dropping out/dimming. You need to rule out a localised problem with the carby first though - it's easy to disturb it.

[Built4thrashing]

Have you upgraded the sensing wire and main charge wired from Alt to battery?

Falcon Alts will self regulate and can charge out at 110Amps. I doubt the factory charge wire will handle that and can burn out.

The sensing wire the alt reads its voltage of goes from the battery through the fire wall to the dash before coming back to the Alt. you can loose voltage and the Alt will try to over charge to compensate for the detected lower voltage.

the idle up on the carby is voltage sensing (I think) so when it detects the voltage is low (when lights turn on ) it tries to idle up the carby. when its high it switches off.

If the Alt is surging its output voltage it can cause your problem.



Fix???

use the factory sensing wire to switch a relay. use this new relay to turn on/off a new sensing wire from Battery to Alt.
Alt will get a better indication of whats happening at the battery and charge accordingly.

[Heideisadog]

I'll try and do some tests on the weekend.

Okay b4t that makes a fair lot of sense! Though I don't completely understand how I do that? Sorry I'm a bit noobish!

[fordem]

Built4thrashing wrote:

the idle up on the carby is voltage sensing (I think) so when it detects the voltage is low (when lights turn on ) it tries to idle up the carby. when its high it switches off.

It's not voltage sensing - there is a diode based wired AND gate wired to the various circuits (blower fan, lights, etc.) - that feeds the idle up.

[Built4thrashing]

ok even still the alt senses voltage and charges accordingly.

[Heideisadog]

I'm going to take some more photos today of how it's set up. If anyone can let me know what should be looked at.
Also there has always been this stray wire with a clip on the end. I'll take a photo of it too. Need some major help :') everything was going so smooth till wiring. Ahhh

[Heideisadog]

What relay should I get?

[Blkfxx]

I wired up a relay to mine today, Just used a 30a since I already had it.

[Heideisadog]

Okay thanks, I'll give it ago!

[Heideisadog]

Old post but thought I should continue it here.

I have now done a G13B engine conversion and I finally got around to swapping my alternator over to the new engine.
I have upgraded the main wire from alternator to battery with 10mm wire and an 80amp fuse in line.
Still having idle surging issues when lights on or there is electrical load. I never did fix the issue with the old engine, so now it's time to.
Do the falcon 110Amp alternators have internal regulators? I have been told that mine could be stuffed.

And to top it off, voltage fluctuates from 12.8V to 13.v3 so it's very low and never goes any higher.
My feeling is stuffed alt. But just want to make sure everything else is correct before I replace.

Hopefully I'm not being a pain. I have read through the whole alt conversion topic too
Thanks for any help

[got_bar_work]

Thats a small wire and fuse for that alt. I would be using 25-35 and a 125a fuse

[Heideisadog]

okay the wiring is an easy fix, but don't think that'll fix the surging. Plus the 80a fuse hasn't blown yet, am I just being over cautious?

[Heideisadog]

I did some testing this afternoon. Tested battery with the car off; Good battery 12.65v no problems there. Car on, no load voltage 13.72v car idling well. Car on, Load applied (headlights and blower + light bar) voltage 14.80v car idling up and down. Almost stalling and then revving back up.

So stumped with what could be causing this...

[Reubs]

Did you wire the alternator's ignition wire (voltage ref./sense wire) through a relay? Not doing so combined with a bad connection somewhere (fuse box, connectors, ignition sw. etc.) will cause the symptoms you have. Have you got clean tight connections on the alternator itself? Was the alternator new or known to be good?

In a good installation with a charged battery you should be seeing 14-14.4V, both at the battery terminals and the alternator's output terminal constantly regardless of load. Outside this range something is not right.

My experience on a brand new Bosch aftermarket EL Falcon alternator voltage is voltages in the range of 14.3 to 14.4V at idle when cold, dropping to 14.2V under a small load, and staying at 14.2V with every electrical load switched on, regardless of RPM.

Also, got-bar-work is on the money - 10mm2 is too small. I personally run 25mm2 only because I couldn't get M6 lugs in 35mm2 at the time. I'm not sure of the specific tripping characteristics of automotive fuses, but half an hour to an hour at max output, such as if your battery collapsed or a lot of winching would probably see that fuse blow.

[Heideisadog]

Hmmm no I haven't. How do I wire that in?
It's a known good alternator and connections onto it are good.

That's what I thought it should be around.

Ah right that makes sense, I'll upgrade the wiringt and would a 100a fuse be ok? Or do you recommend a 125a