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Fraz
#1 Posted : 25 October 2018 21:23:45(UTC)
Fraz

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Thought I'd best start a new thread being as I've just found out that the replacement alternator that I got from an MX5 specialist, is the wrong one.

My 2003 1.8 has a duff alternator (Confirmed by zero difference in voltage showing when the engine is running)  it is a BP6D 80A and the Battery Dashboard light stays on

 

The replacement is a BPE8 65A (Apparently, according to Google, it is from a MK1)

Could the lower output (And the 15.2V at the battery when the engine is running) be the reason that the Battery Light is staying on, even with this replacement alternator?

Thanks again 

2001 MK2.5 S-VT 1.8 in Supreme Blue 22A

2003 MK2.5 Base 1.8 in Sunlight Silver 22V

2003 MK2.5 Base 1.6 in Splash Green 25R
Drumtochty
#2 Posted : 25 October 2018 21:52:40(UTC)
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The Mk1 alternator has an internal voltage regulator.

The Mk2 on the other hand has it's voltage regulated by the cars ECU.

I think the Mk1 alternator will not work in a MK 2 but Rhino will be along to confirm that.
Eddie Cairns

99 Mk2 1.8IS
08 Mk3 2.0 Sport RC sold
18 Mk4 2.0 GT+
Drumtochty Glen, Auchenblae, Laurencekirk,
Aberdeenshire
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Fraz on 26/10/2018(UTC)
rhino666
#3 Posted : 26 October 2018 12:42:23(UTC)
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Unfortunately the MK1 alternator will not work properly on the MK2/MK2.5 and vice versa.

MK1/Eunos alternators(60 & 65 amp Mitsubishi)have builtin regulators whereas the MK2/MK2.5 is regulated by the ecu. They work completely differently. From memory a MK2 alternator will not charge a MK1 car at all, so no voltage change at battery. As you have found a MK1 alternator will charge in a MK2 but at an unstable,unpredicatable voltage, typically high.

Rule of thumb with alternators is that too many amps will not cause issue as battery will only take what it needs. Too low ampage may cause issue as MK2.5 has a lot more going on than the MK1/Eunos. I would advise that you get an 80 amp replacement. I have several original 80 amp alternators, sold with a six month guarantee. Please PM me if interested.  

1997 black 1.6i MK1 - 4/12/2002
1991 red 1.6i Eunos - 21/9/2008

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Fraz on 27/10/2018(UTC)
Fraz
#4 Posted : 27 October 2018 08:27:58(UTC)
Fraz

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Originally Posted by: rhino666 Go to Quoted Post

Unfortunately the MK1 alternator will not work properly on the MK2/MK2.5 and vice versa.

MK1/Eunos alternators(60 & 65 amp Mitsubishi)have builtin regulators whereas the MK2/MK2.5 is regulated by the ecu. They work completely differently. From memory a MK2 alternator will not charge a MK1 car at all, so no voltage change at battery. As you have found a MK1 alternator will charge in a MK2 but at an unstable,unpredicatable voltage, typically high.

Rule of thumb with alternators is that too many amps will not cause issue as battery will only take what it needs. Too low ampage may cause issue as MK2.5 has a lot more going on than the MK1/Eunos. I would advise that you get an 80 amp replacement. I have several original 80 amp alternators, sold with a six month guarantee. Please PM me if interested.  

Dear Mr Rhino

Thanks for your clarification.

Being as I'd bought the replacement alternator from someone who's business is dealing in and breaking MX5's I kind of trusted that he would Supply me with the correct item, as he was aware what my car is.

Obviously not the case, eh?

Thanks also for your kind offer to Supply the correct one but last night I made a long road trip and got another one, this time with the same model number.

I'll be fitting it tomorrow and hopefully saying farewell to the dash-light.

Thanks again

 

2001 MK2.5 S-VT 1.8 in Supreme Blue 22A

2003 MK2.5 Base 1.8 in Sunlight Silver 22V

2003 MK2.5 Base 1.6 in Splash Green 25R
rhino666
#5 Posted : 27 October 2018 10:13:19(UTC)
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Yes, it was a waste of your time.

The 65 amp was probably off a MK1 1.8.

You ahould now have a Hitachi LR180.

One thing I would suggest before fitting is to check that there is no splitting to the aluminium casing where the 4 long bolts go through, top and bottom.

The alternator on  the MK2 seems to attract water and corrosion particularly when car left outside. These splits are caused when galvanic corrosion between the steel bolts and alminium takes place and the expansion splits the aluminium. This eventually takes the armature spin off centre and seizes the alternator. Worth waxoiling the bolt ends and steel central section anyway.         

1997 black 1.6i MK1 - 4/12/2002
1991 red 1.6i Eunos - 21/9/2008

GeriAtric
#6 Posted : 27 October 2018 11:56:46(UTC)
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Hi Rhino,
i have followed the whole of this thread with great interest because my MK2 has always lifted
the battery to 15+V.I changed the battery 3yrs ago thinking that the alternator was flogging itself to
death to support a poor battery.The new battery only had 12 months warranty and is still going strong,
i am a firm believer in the old American Adage (if it aint broke dont fix it).My dilemma is do i start
searching for a problem or maintain the Status Quo and see what develops your advise please.
rhino666
#7 Posted : 27 October 2018 12:28:49(UTC)
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Originally Posted by: GeriAtric Go to Quoted Post
Hi Rhino,
i have followed the whole of this thread with great interest because my MK2 has always lifted
the battery to 15+V.I changed the battery 3yrs ago thinking that the alternator was flogging itself to
death to support a poor battery.The new battery only had 12 months warranty and is still going strong,
i am a firm believer in the old American Adage (if it aint broke dont fix it).My dilemma is do i start
searching for a problem or maintain the Status Quo and see what develops your advise please.

Hi Geriatric 'If it ain't broke, don't fix it' is a great adage and one I try to follow after several lessons learnt first hand in my youth and older, wiser people quoting it to me.

Only 2 rules I can think of for batteries - charging at around 14.6 volts and parasitic current within acceptable limits(20 - 35 ma).

One of the reasons MX5 cars, well MK1 to MK2.5 anyway, work so well is probably the best for purpose original battery on any car(Panasonic) and a reliable and efficient charging system. Combine that with a good smart charger and you can't go wrong.

Charging at anything above around 14.8 volts will start to produce gas in the battery. You will see more bubbling in a lead acid battery and increased heat and volatility in AGM/gel batteries.

This is not healthy and will cause loss of electrolyte in lead acid batteries and premature failure in all batteries as they are being overworked(cooked). 

15+ volts sounds like an unregulated supply to me. What alternator is fitted? If MK2(1998 -2000) would originally have been fitted with a Hitachi LR170, 70 amp unit.

The charging voltage on the MK2/MK2.5 is regulated by the ecu but normally when there is a problem, typically due to water ingress in the passenger footwell and damage to the ecu, the battery stops charging altogether. High voltage on these cars is more likely the wrong alternator fitted.

Get back to me with the alternator make and model - I will check it out for you.          

 

1997 black 1.6i MK1 - 4/12/2002
1991 red 1.6i Eunos - 21/9/2008

Fraz
#8 Posted : 08 November 2018 21:28:09(UTC)
Fraz

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Well, thank you to everyone who has assisted me with this problem.

I can happily report that the battery light is now off and all is well.

Fitted a replacement ECU/immobiliser set and all is good  (Although getting 15V at the battery when the engine is running - which is better than nothing from the alternator, in my book )

Thanks again, you wizards

2001 MK2.5 S-VT 1.8 in Supreme Blue 22A

2003 MK2.5 Base 1.8 in Sunlight Silver 22V

2003 MK2.5 Base 1.6 in Splash Green 25R
Mazda mender
#9 Posted : 09 November 2018 06:56:26(UTC)
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Originally Posted by: Fraz Go to Quoted Post

Well, thank you to everyone who has assisted me with this problem.

I can happily report that the battery light is now off and all is well.

Fitted a replacement ECU/immobiliser set and all is good  (Although getting 15V at the battery when the engine is running - which is better than nothing from the alternator, in my book )

Thanks again, you wizards

Your welcome.

M-m

 

Please feel free to P.M me with any problems or questions.

http://www.mx5oc.co.uk/forum/me.../Mazda_2D00_mender.aspx


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