Changing from 11AC to something with integral regulator

1396midget

1396midget

Well-Known Member
Hi all

In my continuing hunt of odd charging issues the alt has decided to occasionally overcharge (variable intesity lights, variable speed wipers and flashers). Assuming this is a control problem, and coupled with the tired and noisy bearings in the actual body of the alternator, the occasional lighting og the IGN light and the extreme temperature of the alternator body, how much wiring needs to be done to pop a newer ACR alt on there (i've got a spare 65 amp ACR from the K-midget build so would be substanially cheaper than a recon AC one)

I've found a red box in the passenger glovebox area that looks to be the all of pr part of the control system, presumably I can connect up the modern(er) alternator to the correct wires exiting from here to mimic the modern setup, while leaving the regulator box in there in case I need to go back to original at any point. I'm fully aware that any wiring done in this area is going to have to be top notch, I've got some lovely fat cable left over from the K-midget build for taking full alt current and I'd probably stick an ammeter in while I do it.

any help greatly appreciated :)

Rob
 
Rob

IIRC altering the wiring is not a difficult job. As you've mentioned it involves taking the 4TR (the little red box in the passenger glove box) out of the loop as well as altering the ignition light wiring. There are plenty of guides to be found on 't'interweb on how to convert from AC to ACR type alternators. The other thing to bear in mind though is the different mounting bracket for the ACR alternator and probably a different belt to drive it.

Dave
 
I’m currently looking at replacing the 11ac alternator on my p5b at the moment. Further to other posts on the P5B website, the Lucas a127 alternator fits as a direct replacement. This alternator is used on fords, rovers, minis etc etc. there is LH and RH versions available. The one needed on my p5b v8 is the LH version and cost £70 for a 70 amp version. I was just looking at wiring diagrams online and it is simple enough. The old relays become redundant but need to be bypassed, I think by joining the brown/yellow wires. Hope this helps
 
cheers for that, I'll have a look at the P5B site as well, no such thing as too much info!

Interesting about LH and RH alternators, the physics is the same both ways round, so something else must be going on there, perhaps in the way they're made? Though the ones I've taken apart have been 'symmetrical' so to speak, so LH and RH shouldn't make a difference. Could be wrong though...
 
1396midget said:
cheers for that, I'll have a look at the P5B site as well, no such thing as too much info!

Interesting about LH and RH alternators, the physics is the same both ways round, so something else must be going on there, perhaps in the way they're made?
Click to expand...

It's just the mountings, and they can be changed from one to the other anyway.
 
harveyp6 said:
1396midget said:
cheers for that, I'll have a look at the P5B site as well, no such thing as too much info!

Interesting about LH and RH alternators, the physics is the same both ways round, so something else must be going on there, perhaps in the way they're made?
Click to expand...

It's just the mountings, and they can be changed from one to the other anyway.
Click to expand...

The direction of the fan is important too.
 
testrider said:
The direction of the fan is important too.
Click to expand...

It is, but I don't remember seeing a fan that you could fit the wrong way around, changing the side you mount the alternator won't change the direction of rotation, and LH and RH alternators can both be fitted on both the LH & RH sides of the engine.
 
Midget,

As said previously to this post, the LH/RH refers to the bracket lug position on the alternator, not the rotatiing direction of the alternator and not the side of the engine it goes on. As you look at the alternator, there is 120 degrees between the lugs where the alternator is mounted on the engine and the lug that attaches to the adjusting arm. The rear case on the alternator can be removed and rotated so it lines up with either of the lugs on the pulley end and therfore can be LH or RH.

I just bought a new generic make 70amp for €75. The wiring is covered in the other alternator post in this section. Essentially, the big brown wire goes to the starter/battery. The brown yellow is your ignition light, and there is another wire needed that should be connected from the alternator to the battery or as close to it as possible that lets the alternator know what voltage is at the battery and therefore adjusts its out put accordingly. on the p5b, the battety is in the boot, so i will look for the closest point to the battery i can find. i believe the brown purple and brown green become redundant as the regulator is internal.

I will fit my new alternator at the weekend hopefully so will update accorginly, but the info is already on this forum.

Hope this helps
 
Pedantic head on!! Rotate the front case not the rear one as that is hard wired
to the iron core.

Colin

P.S. this is true of Lucas alt's with 3 through bolts, some other makes have 4
through bolts and this does not work.
 
Thanks everyone!

Found one in the alternator drawer.... (dad's managed to collect 7 alternators of varying stages of disaster ranging from seized bearings to crazy outputs)

Midget and Min ones are all right hand mount, but the one from the K-series metro I learned to drive in is a LH mount! yay, it lives on! Swift fight with the serpentine pulley resolved (HA) and it's ready to go in. It looks short enough as well, the midget ones seem longer (pulley to regulator distance) and possibly wouldn't fit in in front of the rocker cover anyway.

Wiring on my P6 presumably was colour coded at some point in its life, now it's all faded whitey-grey (sort of cloth covering)...

My plan is to intercept the wiring at the point where it enters the separate regulator and join it up there, bypassing the regulator and feeding into the loom where the output of the regulator goes. I'm planning to fit an ammeter in as well when I do this - I like to know what's going on!

Wiring the Ignition light line straight to the alt should work when I work out which wire it is. Would have done it this weekend but rebuilding the rear brake callipers were rather more complicated than I expected.

now to just find the time to do it...
 
Installed my new alternator last weekend. Very Simple. Direct swap. I had to get a shorter fan belt so i could still use the original adjusting bracket. Removed belt was marked 1150mm. Replacement belt is 1125mm.

The original charging wire and ignition light wires fitted straigh on. The original voltage regulator wires are now redundant. I had to bridge out the ignition light relay (3ac) as it is no longer needed either. This is straight forward - remove pulg, join brown/black to brown/yellow. (1973 P5B Coupe)

I also disconnected the 4tr and the 6** relays as they are redundant.

14.4 volts at the battery now; which is nice, but more importantly, when the fan kicks in, the ammeter jumps to an indicated 30 amps, which means i was never ever going to be able to keep the battery charged with the old alternator. i turned on all of the electrics including brake lights and the ammeter still shows positive, so all is good.

i bought mine from minispares.com for approx £60 including the pulley which is the best value. The original i bought in Ireland had no pulley and it would have cost £30 to buy the pulleyt and fan and have it shipped. So i flogged the "irish" one to a mate for his ford and bought the minispares one. :D
 
Good work Baldrick. For those not interested in modifying the wiring loom I spoke to a company at the NEC who could rewind an 11AC alternator to up the output to 65A or 70A. Previously I was unaware that this was possible to do.
 
Thats good to know Testrider. Any chance you can post the company name and details? I might get my original upgraded. Always good to have a spare. I will also post the info over on the P5 website as there are plenty of others that would be interested. :)
 
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