IPD sale XeMODeX - Experts in Volvo Electronics
Did you know? 🤔
Logged in users can get email notification of topic replies Log in or register (free).
Amazon Link Buy your stuff using this and it helps MVS!

Alternator installation question

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
1997 - 2000 S70, S70 AWD
1997 - 2000 V70, V70 AWD
1997 - 2000 V70-XC
1997 - 2004 C70

User avatar
amblerman
Posts: 226
Joined: Wed Jan 18, 2017 3:29 pm
Year and Model: 1999 s70
Location: Pennsylvania
Has thanked: 1 time
Been thanked: 16 times
United States of America
amblerman

Alternator installation question

Post by amblerman » Tue Sep 10, 2019 7:13 am

Hi folks,

I just got a new alternator for my 99 s70.

It came with a tag that states.
1: Batter must be fully charged prior to installation of alternator.
2: Battery cables must be removed from batter prior to connecting opposite side of cables to alternator Failure to do so may damage diodes.

I already have the battery fully disconnected but that last statement got me thinking. Why would not fully disconnecting battery damage diodes? Also, if you don't have battery fully disconnected, does this also imply there is a correct order in which the battery cables need to be reconnected so you don't get into the same situation and damage diodes?

I was planning on reconnecting all positive connections first and then the negative last.

Can anyone explain what combination of having the cables attached or attaching in incorrect order can damage diodes?

Thanks
-A



Herb Goltz
Posts: 117
Joined: Wed Jun 15, 2011 8:47 am
Year and Model: V70 2000
Location: Aurora, ON, Canada
Has thanked: 1 time
Been thanked: 1 time
Canada
Herb Goltz

Re: Alternator installation question

Post by Herb Goltz » Tue Sep 10, 2019 7:29 am

I have always connected the negative last, and have never had a problem. I think the real concern is swapping the pos and neg, which could damage the diodes, which are "one way streets" for the current.



User avatar
abscate
MVS Moderator
Posts: 18186
Joined: Sun Feb 17, 2013 5:54 pm
Year and Model: 99T5 ,99S70,2005V70
Location: NYC, ALBANY NY
Has thanked: 200 times
Been thanked: 647 times
Trinidad & Tobago
abscate

Re: Alternator installation question

Post by abscate » Tue Sep 10, 2019 10:09 am

I think its just a liability clause where they want you to connect the battery last, so that if you screw that up, you made the mistake.

It is correct practice to connect positive first and negative last, but there is no reason to disonnect the positive if the negative is off and isolated so it can't touch the battery post.


Empty Nester
A Captain in a Sea of Estrogen
1999-V70-T5M56 2005-V70-M56 1999-S70 VW T4 BMW

User avatar
amblerman
Posts: 226
Joined: Wed Jan 18, 2017 3:29 pm
Year and Model: 1999 s70
Location: Pennsylvania
Has thanked: 1 time
Been thanked: 16 times
United States of America
amblerman

Re: Alternator installation question

Post by amblerman » Tue Sep 10, 2019 12:15 pm

abscate wrote:
Tue Sep 10, 2019 10:09 am
I think its just a liability clause where they want you to connect the battery last, so that if you screw that up, you made the mistake.

It is correct practice to connect positive first and negative last, but there is no reason to disonnect the positive if the negative is off and isolated so it can't touch the battery post.

The reason I disconnected the positive side of the batter is to eliminate the possibility of my wrench hitting a ground while tightening the positive cable (which would be live if the positive terminal on battery were connected) on the alternator B+ connection.



User avatar
amblerman
Posts: 226
Joined: Wed Jan 18, 2017 3:29 pm
Year and Model: 1999 s70
Location: Pennsylvania
Has thanked: 1 time
Been thanked: 16 times
United States of America
amblerman

Re: Alternator installation question

Post by amblerman » Tue Sep 10, 2019 12:18 pm

Herb Goltz wrote:
Tue Sep 10, 2019 7:29 am
I have always connected the negative last, and have never had a problem. I think the real concern is swapping the pos and neg, which could damage the diodes, which are "one way streets" for the current.
Thanks.

I figured swapping +/- would be a big issue but I was wracking my brain trying to figure out how connecting it normally (ie proper +/-) would be an issue. I couldn't come up with a scenario as it's impossible to connect the alternator wrong on these cars.

ie: ground for alternator is bolts to engine, 1 +B wire and the tiny wire that connects with a plug. Impossible to wire it up incorrectly.

-A



User avatar
BEJinFbk
Posts: 3639
Joined: Sat Jan 05, 2008 10:32 pm
Year and Model: '98 V70 R
Location: Fairbanks, Alaska
Has thanked: 20 times
Been thanked: 35 times
United States of America
BEJinFbk

Re: Alternator installation question

Post by BEJinFbk » Tue Sep 10, 2019 12:57 pm

If the negative terminal of the
battery is disconnected, it doesn’t
matter if the wrench on ANY positive
connection hits anything anywhere.
No negative still means no power flow.

That’s why you always make negative
first to disconnect, last to connect. 👍


'98 V70 R - Well Equipped for Life Up North... ;)

User avatar
amblerman
Posts: 226
Joined: Wed Jan 18, 2017 3:29 pm
Year and Model: 1999 s70
Location: Pennsylvania
Has thanked: 1 time
Been thanked: 16 times
United States of America
amblerman

Re: Alternator installation question

Post by amblerman » Tue Sep 10, 2019 1:04 pm

BEJinFbk wrote:
Tue Sep 10, 2019 12:57 pm
If the negative terminal of the
battery is disconnected, it doesn’t
matter if the wrench on ANY positive
connection hits anything anywhere.
No negative still means no power flow.

That’s why you always make negative
first to disconnect, last to connect. 👍
doh.png
Oh my gosh. I don't know what I was thinking. Of course that's true. What I was talking about would be true if and only if the negative was till connected .

So.. I need to amend my statement.. I don't know why I disconnected the + and - other than it's easy now that I have quick disconnect style terminal ends.
:D
Man.. I can't believe I made such a bone headed mistake....
-A
You do not have the required permissions to view the files attached to this post.



Post Reply