Alternator changed - help needed!

[igould]

I've got a (non-original) Bosch alternator in my '77 RR which I need to get wired up.

The terminals on the back don't match the standard connection as shown in the photos.

Which wire goes to which terminal?

http://www.aulro.com/modules.php?set_album...=view_photo.php

http://www.aulro.com/modules.php?set_album...=view_photo.php

I know I'll need to beef up the alternator in the future, but at the moment I'm only concerned with getting the car on the road.

Any help/wiring diagrams would be greatly appreciated.

Thanks, Ian

[FridgeFreezer]

Can't see the photos (links) without being logged in to that forum, try using a different photo host or e-mail them to me and I'll host them for you.

Or just tell us what terminals you have on the wire & alternator. If you have the old alternator you should be able to look at the plug and match the terminals up.

[FridgeFreezer]

Righty, piccies ahoy!

I haven't got my thinking brain in tonight so will have to leave it to the clever people of this forum to decode those!

[fisha]

i would expect the browns all to go onto the D+ bolted terminal.

brown is un fused live and the D+ terminal is the only one of those labelled that would handle the current.

The small brown probably runs to the ign barrel area whilst the larger ones to the main fuses and / or starter motor.

The brown yellow should go to the no-charge light and so again - so it may be the bolted B+ or possibly D+

dont know

[FridgeFreezer]

Well I'm now sufficiently awake to make a wild guess

Big thick brown ones are B+ (battery positive)

Brown/yellow is charge warning light so probably goes to the D+ spade terminal

Other two look like RFI surpressor so can be left as-is / unconnected.

[jwriyadh]

The two thick browns go the B+, this alternator output to battery positive.

The brown/yellow goes to D+, this is from the charge warning lamp.

The remaining thin brown is probably for voltage sensing and should remain disconnected and insulated.

Some RRs used battery sensing when fitted with ACxx series alternators.

To confirm that your new alternator is correctly connected start and warm up the engine, put voltmeter across the battery pos and neg lugs, then raise the engine revs to around 1500-1800 rpm and hold for a couple of minutes.

The voltage should rise slowly to a maximum of 14.2 volts, if it rises any further get a sparky to look at it.

jw

[igould]

Thanks very much, people.

I appreciate your help.

Looking forward to getting it hooked up and testing, but unfortunatley won't have time to get to it for a week or so.

Anyway,

Thanks again for all the help,

Ian

[igould]

I got onto it sooner than I thought, so I thought I'd post the update.

Everything is hooked up as per your suggestions and it works beautifully.

Took her out for the first run since I got it (just around the local streets), and it runs like a charm. Heaps of grunt and a beautiful exhaust note. Looking forward to hitting some tracks sson.

Just one more question: When I turn the ignition on, before starting the motor, the tacho jumps to around 800rpm. Seems to read Ok when running though. Any clues?

Thanks for your help.

Ian

[FridgeFreezer]

Glad it worked!

Electronic tachos work from the coil*, counting pulses as the coil fires. When you turn the ignition on you cause a pulse to the coil, which can make the tacho jump. I see the same thing on the MegaSquirt at switch-on, the needle jumps up to about 800 then drops.

* = Before some (other) pedant points it out, some tachos work from the alternator W terminal and some work from the ECU. Also if you have the ignition amp under the coil there is a dedicated tach feed from that for the ECU / tacho.