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Reverse Motor Wiring
Jamesc - 26/1/15 at 01:32 PM

I'm about to embark on wiring up the starter motor which will serve as the reverse drive.

It's a VAG starter, like most use but I have a few questions;

- What's the max load likely to be? i.e. how much current will the wire/relay etc need to handle?

- How is the solenoid/starter wired up on the motor terminals? (Just to check I'm correct)

Any help would be appreciated. I've wired the rest of the car myself and I'm fairly confident with electrics, but I'm more cautious of this!

Cheers!

loggyboy - 26/1/15 at 02:13 PM

I suspect the main supply will need to be a sturdy gauge of wire (4awg/5mm2). EDIT- no need for a relay as thats what the solenoid does, and no need for a fuse as will be 50amps + so could only be a mega fuse or similar.
Earth should be ok from simply bolting to the chassis, if not then an equal wire to earth from one of the mounting bolts.
Solenoid feed from button need not be anything too large, and is not linked to the supply in anyway.

[Edited on 26-1-15 by loggyboy]

Jamesc - 26/1/15 at 03:00 PM

That's my thing I've learnt today! OK, so no need for a relay, thanks.

Would 4awg wire be man enough though? That's about 45 amps I believe? I will add a mega fuse as well as a fuse on the switch to solenoid cable most likely.

daviep - 26/1/15 at 04:39 PM

Around 25mm2 would be more appropriate for the main feed to the starter.

Regards
Davie

Barkalarr - 26/1/15 at 08:14 PM

This any good ??

Description
Description

Jamesc - 26/1/15 at 08:19 PM

quote:
Originally posted by Barkalarr
This any good ??

Description
Description


Yes thanks mate, I did see that earlier but wasn't sure on the gauge of wire needed or how manly the switches needed to be.

Also, is there any need for the relay?

Barkalarr - 26/1/15 at 08:36 PM

quote:
Originally posted by Jamesc
quote:
Originally posted by Barkalarr
This any good ??

Description
Description


Yes thanks mate, I did see that earlier but wasn't sure on the gauge of wire needed or how manly the switches needed to be.

Also, is there any need for the relay?



Only reason I put a relay in there was so that I couldn't engage the reverse unless I was in neutral. I didn't want to inadvertently push the reverse switch while the engine could theoretically be moving forward.

Jamesc - 26/1/15 at 08:46 PM

quote:
Originally posted by Barkalarr
quote:
Originally posted by Jamesc
quote:
Originally posted by Barkalarr
This any good ??

Description
Description


Yes thanks mate, I did see that earlier but wasn't sure on the gauge of wire needed or how manly the switches needed to be.

Also, is there any need for the relay?



Only reason I put a relay in there was so that I couldn't engage the reverse unless I was in neutral. I didn't want to inadvertently push the reverse switch while the engine could theoretically be moving forward.


Good thinking. That's what I was planning, so will also need a relay.

What gauge wire did you use to the solenoid?

Barkalarr - 26/1/15 at 08:51 PM

quote:
Originally posted by Jamesc
quote:
Originally posted by Barkalarr
quote:
Originally posted by Jamesc
quote:
Originally posted by Barkalarr
This any good ??

Description
Description


Yes thanks mate, I did see that earlier but wasn't sure on the gauge of wire needed or how manly the switches needed to be.

Also, is there any need for the relay?



Only reason I put a relay in there was so that I couldn't engage the reverse unless I was in neutral. I didn't want to inadvertently push the reverse switch while the engine could theoretically be moving forward.


Good thinking. That's what I was planning, so will also need a relay.

What gauge wire did you use to the solenoid?


I can't remember but since the solenoid is low current, just normal gauge wire would be fine.

Jamesc - 10/2/15 at 09:05 AM

quote:
Originally posted by daviep
Around 25mm2 would be more appropriate for the main feed to the starter.

Regards
Davie


25mm2 is rated at 170A, would this be enough? My electrical knowledge isn't the best, but the battery and quoted starter draw is well over 400A.

485A cable is 70mm2 - Is that overkill?

Hopefully someone with some more knowledge and experience can help me out!

Angel Acevedo - 10/2/15 at 05:39 PM

A simpler answer would be to use the cable used on the original application.
I would even go to a size smaller as you most likely never use the reverse for as long as you would the starter on a cold day...
My humble opinion though.
Best regards
Angel Acevedo

40inches - 10/2/15 at 06:29 PM

I fitted a 250amp Mega fuse, it never blew, but the original 150amp did, after a few uses.