Alternator upgrade

[allanv6gt]

Hi folks,

Following a rebuild and some extra electrical bits, it seems my old Lucas 15ACR Alternator is now struggling. Barely holds enough volts on the guage wjhen headlight, driving lights are switched on ...don't ask what happens when 15A thermo fan cuts in.

So...upgrade time.

The car is a genuine V6 and was happily running the same 15ACR/28A alternator (before rebuild) in a different shell (and therefore wiring loom - more resistance here?). Only prev. noticed some measured voltage drop when headlights were used, but still well into the green range on Volts guage. I know a V6 should have a 17ACR, but 15ACR is what I had at the time the 17ACR bearings failed and all seemed ok in use (for 10 years...).

Now...question re wiring capacity.

Can I upgrade from 17ACR/36A wiring to higher amps without letting the smoke in the wiring out? Remember the V6 charges via the ignition switch circuit and I'm told this can be a source of BBQs under the dash.
(Really scary seeing smoke rise from underneath when driving along...trust me on this one !! Another war story...)

I see 18ACR/43A are/were available and a straight fitment swap.

Anyone followed this path with success?
I don't really want to chop my reco'd wiring loom. If necessary, I'll just get a reco'd 17ACR to fit.

[caprispecial]

I bought a new 17acr from ebay uk. It supposedly puts out an uprated 42 amps, its probably of chinese origin but surely couldnt be any worse than genuine lucas? Anyway so far it works just fine.
To solve the problem of all that power going thru the ignition switch run a suitable wire from the alternater around the front and up to the battery.

[Engine Guy]

Originally Posted by allanv6gt

So...upgrade time.

The car is a genuine V6 and was happily running the same 15ACR/28A alternator (before rebuild) in a different shell (and therefore wiring loom - more resistance here?). Only prev. noticed some measured voltage drop when headlights were used, but still well into the green range on Volts guage. I know a V6 should have a 17ACR, but 15ACR is what I had at the time the 17ACR bearings failed and all seemed ok in use (for 10 years...).

Now...question re wiring capacity.

Can I upgrade from 17ACR/36A wiring to higher amps without letting the smoke in the wiring out? Remember the V6 charges via the ignition switch circuit and I'm told this can be a source of BBQs under the dash.
(Really scary seeing smoke rise from underneath when driving along...trust me on this one !! Another war story...)

I see 18ACR/43A are/were available and a straight fitment swap.

Anyone followed this path with success?
I don't really want to chop my reco'd wiring loom. If necessary, I'll just get a reco'd 17ACR to fit.

Not quite...

The wiring that runs through the ignition switch is actually just the 'exciter / warning light circuit' of the alternator...not the actual charging circuit.

If you look at the wiring harness that plugs into the alternator, you'll see 1 smaller wire (this runs to Ign/warning light) and two heavier wires - these heavier wires run to the battery positive terminal.

So it would be wise to check that these heavier wires are in good condition - they may even need to be upgraded - from the Alternator to the Battery
(some higher output alternators have a lug&bolt connection for the charging wires)
You may also need to check that your battery is in good condition and suitable for a higher output alternator.

Also bear in mind that a higher output (amp) alternator might need a upgraded belt to drive it! and it will put more load on the engine...

Cheers
Engine Guy

[caprispecial]

A big problem with the capri is the wiring was designed without relays meaning that all the power to run the lights, horn etc must go thru the switches and loom connectors, which causes trouble over time.
To lessen this load I set up relays for high beam, low beam, horn, driving lights and thermatic fan and tucked it all out of sight in behind the grille. All this now has a direct feed and fuses from the battery. The original loom and switchs now only operate the relays which is only very low load.
I also have fuses and relays behind the plastic panel on the passenger side of the dash for other stuff such as electric fuel pump.
So none of the modern stuff is visible to spoil the original look.

[Engine Guy]

Originally Posted by caprispecial

A big problem with the capri is the wiring was designed without relays meaning that all the power to run the lights, horn etc must go thru the switches and loom connectors, which causes trouble over time.
To lessen this load I set up relays for high beam, low beam, horn, driving lights and thermatic fan and tucked it all out of sight in behind the grille. All this now has a direct feed and fuses from the battery. The original loom and switchs now only operate the relays which is only very low load.
I also have fuses and relays behind the plastic panel on the passenger side of the dash for other stuff such as electric fuel pump.
So none of the modern stuff is visible to spoil the original look.

Yes, you are correct there. The original wiring was designed to handle the electrical loads that are original in the car. if you increase the load then it's best to install relays to switch these new 'higher current' loads..

many people just bolt on extra circuits & lights etc and wonder why the electrical system fails...

Cheers
Engine Guy

[allanv6gt]

thanks folks.
Already have relays/fuses for headlights, driving lights and thermo fan.

Just pondering current carrying capacity of that 40yr old wiring loom on charge upgrade.

Interstingly, The V6 Capri has two charge wires from the laternator, but one ends down near the chassis rail RHS, with the other going to ignition switch then off to the battery....which is why the ignition switch can get cooked.

If running an extra wire from alternator to battery direct, what ampage wire should be used ? Of course, the 36Amp alternator output should only ever be a momentary maximum.