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Old 03-25-2019, 06:47 AM   #1
JGood
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m60 e30 guys, can you please test something for me...

Can anyone who has a properly running e30 m60, with a normal 500rpm idle speed (after it warms up and settles), please check your voltage at idle?

I need the following:

1. Voltage at idle, with engine warmed up and RPM settled, with NO lights, A/C, blower motor, etc. *After* the engine is warmed up and settles to the lowest idle speed

2. Voltage at idle with headlights and blower motor on high (This is what I'm really looking for)


I ask because I'm on my third Reman alternator and second battery, and still seeing only 12.3v at idle with lights and blower on. Without them on, it's 14v. If I give it any throttle to raise the RPM, it'll hold 14v with everything on as well. It's almost like the alternator output is not enough at 500rpm, but that is the spec for m60's. My battery voltage with engine off is 12.6v.
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Old 03-25-2019, 12:21 PM   #2
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Will check
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Old 03-25-2019, 03:41 PM   #3
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Will check
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Old 03-26-2019, 03:44 PM   #4
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will check... Jean remind me
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Old 03-26-2019, 04:46 PM   #5
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Idle, 14.05v
Headlights and Blower on 4, 12.4v
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Old 03-27-2019, 05:30 AM   #6
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Sweet, so it's normal.

I didn't like it.

Pin 64 of the DME is a +12v input from the a/c compressor to bump the idle up about 50 rpm. I hooked this up to switched +12v power at the main relay, and ran in through an extra switch in my center console (the rear window lockout button). So it now idles at about 550rpm, and holds 13+v with all accessories running. Even when the electric radiator fan kicks in, it only drops to 12.6v, still maintaining battery voltage. The power windows are significantly faster at idle, and I no longer get a dimming/brightening of lights or speeding up/slowing down of the blower motor as the engine comes on or off idle. And it's on a switch, so I can always bump the idle back down if I desire.

I'm also going to try pin 81, that is a +12v input on m60 e34's from the headlight switch that is activated with low beams on. I bet that is another similar RPM bump. I may find that is better suited.
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Old 03-27-2019, 06:34 AM   #7
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Yeah looks like it's normal but Id wait for the others to chime in. Your battery usage is surprising to me, but the alternator is NOT.

How many years did you get out of your first battery?

I have a hard time trusting Reman alternators and starters. I sell a lot of them, and the number that get returned and warrantied either straight out of the box or within the first few months is baffling to me (Good Bosch units too). I'd almost prefer to sell good used units instead of reman's. There's even a local shop that will go the junkyard for original used alternators and starters because they trust them more than reman.

That being said, my alternator has a date stamp of 1996. It works great but I do have a constant fear of it going out.
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Old 03-27-2019, 07:43 AM   #8
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6 years. I just meant this 'issue' existed with both batteries, and all 3 alternators, so as to remove the inclination of everyone to suggest they are faulty, as I had assumed they were until replacing them.

I'm content now with the idle bumped up. I'm just going to check the light switch input functionality, and possible do something with that. It would be nice to have it fully functional as it would be in an e34.
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Old 04-02-2019, 01:57 PM   #9
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That's good info to know, I might try this also as my idle seems a bit lumpy once warm and windows can be slow...might also help the battery life
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Old 04-02-2019, 03:38 PM   #10
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Quote:
Originally Posted by ArtFoodBMW View Post
Yeah looks like it's normal but Id wait for the others to chime in. Your battery usage is surprising to me, but the alternator is NOT.

How many years did you get out of your first battery?

I have a hard time trusting Reman alternators and starters. I sell a lot of them, and the number that get returned and warrantied either straight out of the box or within the first few months is baffling to me (Good Bosch units too). I'd almost prefer to sell good used units instead of reman's. There's even a local shop that will go the junkyard for original used alternators and starters because they trust them more than reman.

That being said, my alternator has a date stamp of 1996. It works great but I do have a constant fear of it going out.



The remans are being sent overseas, and more often than not, they are re-using the old regulators. Usually when diagnosing a car, I will change the regulator first, if that's not the issue, then I keep the regulator and install it in the purchased reman.
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Old 04-02-2019, 03:42 PM   #11
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Its not the same engine, but even my m20 with headlights on 12.4ish at the battery at idle. I thought i had a bung alternator but there is no battery light though so the alternator is doing its thing. seemed low to me too. But the battery never goes flat. I originally thought the wiring to my mega squirt was dodgy and was showing a low value, but nope, 12.4ish is fairly normal it seems.

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Old 04-02-2019, 07:53 PM   #12
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Quote:
Originally Posted by e30davie View Post
Its not the same engine, but even my m20 with headlights on 12.4ish at the battery at idle. I thought i had a bung alternator but there is no battery light though so the alternator is doing its thing. seemed low to me too. But the battery never goes flat. I originally thought the wiring to my mega squirt was dodgy and was showing a low value, but nope, 12.4ish is fairly normal it seems.



I don't think that's normal. m20's idle more in the 700rpm range, that should do 13v or more from what I remember from my last m20 powered e30. My m30 e34 idles around 700 and sits at 13.7 regardless of lights/blower/air etc...


The reason my m60 was low is because I was loading it with lights and the blower, at 500RPM. m60's have an idle bump with lights on to prevent the voltage drop. Not an issue on m20's as they are not intended to idle that low, ever.
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Old 04-02-2019, 08:12 PM   #13
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E30davie, 12.4 isn't charging your battery. Battery cells rest at 12.6, and the m20 is a low voltage setup as it is. I find most of them will see low 13's loaded at the battery, but 14.3-8 at the alternator output. Might want to diagnose further.
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Old 04-02-2019, 09:43 PM   #14
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Hmm I will have another look. this was like 6 months ago, and haven't had any troubles.
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Old 04-03-2019, 04:46 AM   #15
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When you drive, the RPM's are much higher, so it likely shoots up into the high 13's, low 14's, so it charges the battery then. You probably just need a new voltage regulator.
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