Alternator or other issue?

An area for topics concerning SW20's

Moderator: Moderators

Forum rules
This area is dedicated to technical discussions concerning SW20's. Please try to spell correctly because this will help people find information later if they are using search functionality. If you need assistance with your car and want to host a spanner day, please use the appropriate section of the forum: http://mr2.org.nz/phpbb3/viewforum.php?f=35 Thank you.
User avatar
GDII
Forum Moderator - MR2OCNZ
Posts: 4860
Joined: Sun Jul 10, 2011 5:13 pm
Stomping Ground: Wellington
Prime Mover: SW20
First name: Phill

Re: Alternator or other issue?

Post by GDII »

It's possibly the belt being loose?
MR2s are notorious for eating alternators. I've had 9 failures in 7 different ways over 14 years. First one wore out, second one bust a diode then the third one has had many failure modes. It's now got worn bearings that need replaced.
1990 SW20 MR2 G-Limited (GEN4 3SGTE swap early stages)
1996 AE101 Corolla Sprint NZ New Daily
1990 EP81 Starlet XL (Sold)
1990 EE90 Corolla XL (Sold)
Instagram https://www.instagram.com/sw20glimited/

Ballist1x
Guest of the Club.
Posts: 6
Joined: Thu Aug 04, 2022 8:24 am
Stomping Ground: Bay Of Plenty
Prime Mover: SW20
First name: Nick

Re: Alternator or other issue?

Post by Ballist1x »

I suspect mine is down to user failure, I.e dripped some oil while doing an oil change a couple of weeks ago ..

I'm going to do some basic diagnostics tonight when I get home from work.

Ballist1x
Guest of the Club.
Posts: 6
Joined: Thu Aug 04, 2022 8:24 am
Stomping Ground: Bay Of Plenty
Prime Mover: SW20
First name: Nick

Re: Alternator or other issue?

Post by Ballist1x »

GDII wrote: ↑
Thu Aug 04, 2022 4:04 pm
It's possibly the belt being loose?
MR2s are notorious for eating alternators. I've had 9 failures in 7 different ways over 14 years. First one wore out, second one bust a diode then the third one has had many failure modes. It's now got worn bearings that need replaced.
Cleaned up a couple of grounds at the rear. Checked the 7.5v fuses fromt and back.

So I charged the battery up to 12.4v ignition off.

Started the car and the voltage drops to 11.9v @1400 rpm.

Revved it a few times no increase in voltage. Put lights on etc and it went down to 11.8x volts.

I wasn't fully able to unplug the 3 pin oval from the alt as I just couldn't get it out to test each pin.

So I'd say having read up on the subject it's 30/70 % either the middle wire or a new alternator time...

User avatar
GDII
Forum Moderator - MR2OCNZ
Posts: 4860
Joined: Sun Jul 10, 2011 5:13 pm
Stomping Ground: Wellington
Prime Mover: SW20
First name: Phill

Re: Alternator or other issue?

Post by GDII »

I'd say new alternator. 9 out of 10 times it is.
1990 SW20 MR2 G-Limited (GEN4 3SGTE swap early stages)
1996 AE101 Corolla Sprint NZ New Daily
1990 EP81 Starlet XL (Sold)
1990 EE90 Corolla XL (Sold)
Instagram https://www.instagram.com/sw20glimited/

Ballist1x
Guest of the Club.
Posts: 6
Joined: Thu Aug 04, 2022 8:24 am
Stomping Ground: Bay Of Plenty
Prime Mover: SW20
First name: Nick

Re: Alternator or other issue?

Post by Ballist1x »

You know what's weird, I charge my car battery to 12.7v (checked with multi meter).

And I leave charger plugged in and I turn on my ignition but don't start the engine.

I get the hotcat sensor light and the battery discharge symbol.

But if the car isn't running, of course the alternator isn't running so why wpuld these lights even come on? Does this indicate a wiring issue somewhere as to my simply mind wouldn't they only be an error when idling due to low voltage?

User avatar
GDII
Forum Moderator - MR2OCNZ
Posts: 4860
Joined: Sun Jul 10, 2011 5:13 pm
Stomping Ground: Wellington
Prime Mover: SW20
First name: Phill

Re: Alternator or other issue?

Post by GDII »

Those lights go on because the alternator is not charging because the engine is not running. It's normal.
If the engine is running and they are on the alternator is definitely not charging.
1990 SW20 MR2 G-Limited (GEN4 3SGTE swap early stages)
1996 AE101 Corolla Sprint NZ New Daily
1990 EP81 Starlet XL (Sold)
1990 EE90 Corolla XL (Sold)
Instagram https://www.instagram.com/sw20glimited/

Ballist1x
Guest of the Club.
Posts: 6
Joined: Thu Aug 04, 2022 8:24 am
Stomping Ground: Bay Of Plenty
Prime Mover: SW20
First name: Nick

Re: Alternator or other issue?

Post by Ballist1x »

Update; new Alternator fitted and problem is now fixed.

User avatar
GDII
Forum Moderator - MR2OCNZ
Posts: 4860
Joined: Sun Jul 10, 2011 5:13 pm
Stomping Ground: Wellington
Prime Mover: SW20
First name: Phill

Re: Alternator or other issue?

Post by GDII »

Excellent. :D
1990 SW20 MR2 G-Limited (GEN4 3SGTE swap early stages)
1996 AE101 Corolla Sprint NZ New Daily
1990 EP81 Starlet XL (Sold)
1990 EE90 Corolla XL (Sold)
Instagram https://www.instagram.com/sw20glimited/

Post Reply