Alternator not charging; known good alternator and battery. Any Ideas?
- Thread starter DiscoClay
- Start date
Okay, sorry for the long delay.
The problem was two-fold: bad diodes and bad regulator.
The alternator was draining [shorting] to ground at an equivalent of a ~1.5amp draw. As my 1amp trickle charger couldn't keep up over night it was sucking the battery down.
Additionally, the regulator was not regulating.. so under charging at low rpm [discharging] and overcharging at high rpm [16.5v at 4000rpm].
Luckily my 14cux is still alive!
Thanks to everyone for the angles!
I picked up a used alternator (with good diodes and bearing) with a bad regulator and popped in a new regulator and all is well. It runs up to 14.5v at ~2300rpm and stays above 12.6 at idle.
One other todo:
My shortened belt is a little loose, so I need to get a slightly shorter one.. I think its causing slippage when the alternator is heavily loaded [see: https://discoweb.org/index.php?thre...draulic-power-steering-conversion-done.101124 ]
The problem was two-fold: bad diodes and bad regulator.
The alternator was draining [shorting] to ground at an equivalent of a ~1.5amp draw. As my 1amp trickle charger couldn't keep up over night it was sucking the battery down.
Additionally, the regulator was not regulating.. so under charging at low rpm [discharging] and overcharging at high rpm [16.5v at 4000rpm].
Luckily my 14cux is still alive!
Thanks to everyone for the angles!
I picked up a used alternator (with good diodes and bearing) with a bad regulator and popped in a new regulator and all is well. It runs up to 14.5v at ~2300rpm and stays above 12.6 at idle.
One other todo:
My shortened belt is a little loose, so I need to get a slightly shorter one.. I think its causing slippage when the alternator is heavily loaded [see: https://discoweb.org/index.php?thre...draulic-power-steering-conversion-done.101124 ]
I chased around smilar issues for over a year. Drove me nuts. I had an alternator rebuilt as well as bought used ones. It would get better then get worse. I was avoiding buying a new alternator because an OEM one was a lot of money and everyone is always all "the ones made in china suck and fail!!!"
I ended up thinking I was getting a deal from Atlantic British and getting an "OEM one" from them for under $200. Turned out it said made in china right on it. I hooked it up and all the problems went away and I am always showing high charge rates. I used to dip down below 12V on my meter when idled at a light with the heater on high, radio, and headlights on. Those problems are no more - zero issues, none.
I think your 12.6 is stil low, but up to you. I would just bite the bullet and get a new alternator from AB to be 100% sure it wasn't a coumpound issue.
Tom
I ended up thinking I was getting a deal from Atlantic British and getting an "OEM one" from them for under $200. Turned out it said made in china right on it. I hooked it up and all the problems went away and I am always showing high charge rates. I used to dip down below 12V on my meter when idled at a light with the heater on high, radio, and headlights on. Those problems are no more - zero issues, none.
I think your 12.6 is stil low, but up to you. I would just bite the bullet and get a new alternator from AB to be 100% sure it wasn't a coumpound issue.
Tom
While you're route is the right one.. I am a' glutton for punishment.
I agree that 12.6v is too low .. heck, that's essentially the base voltage of the new healthy battery.
I will swap the belt for a tighter one tomorrow and report back.
Then it's diodes and the slip rings.
Update: New, shorter multi V-belt (7PK1664, GoodYearBelts.com: 1070655) installed. It is a little too tight.. not enough to kill bearings, but enough that the tensioner does not have enough travel to allow it to slip on; I pulled the top alternator bolt and dropped the alt just enough to install it. The tension really wasn't bad so I'll go with it for now.
Unfortunately this did not address the low voltage charging problem. It is certainly charging..but it's just not charging much. With no/light load (highway ~2500rpm @70ish mph) it charged at 14.5 for about 20 minutes and then it dropped down to 12.6 like a switch was thrown.
Also, when I got back from a ~2hr drive I put the thermal-IR gun on the alternator and it was showing 300ºF at the outer stator windings (the ones you can see from the top-center). That seems pretty hot imo... Hell, that's hotter than the exhaust manifold was showing at that stage of cool down.
RVR OVR is right, I think I am splashing good money after bad on this one.
Does anyone know of interesting and easy oversized alternators and or smaller (7-rib) pulleys? I wouldn't mind finding a pulley that's 1/4 inch smaller in diameter.
Unfortunately this did not address the low voltage charging problem. It is certainly charging..but it's just not charging much. With no/light load (highway ~2500rpm @70ish mph) it charged at 14.5 for about 20 minutes and then it dropped down to 12.6 like a switch was thrown.
Also, when I got back from a ~2hr drive I put the thermal-IR gun on the alternator and it was showing 300ºF at the outer stator windings (the ones you can see from the top-center). That seems pretty hot imo... Hell, that's hotter than the exhaust manifold was showing at that stage of cool down.
RVR OVR is right, I think I am splashing good money after bad on this one.
Does anyone know of interesting and easy oversized alternators and or smaller (7-rib) pulleys? I wouldn't mind finding a pulley that's 1/4 inch smaller in diameter.
Attachments
Did all that. Grounds are good.
With good diodes and new regulator it is still exhibiting this wonky behavior.
I agree that it acts like a loose ground but everything checks out. Many years ago I had an engine<->chassis/body ground problem [woven copper cable from engine to firewall was overheated and thus heavily oxidized].
Do any of you guys have normal operating temps for the alternator?
I am looking at installing the late d2 alternator for the extra amps [https://www.maniacelectricmotors.com/new150ampalf1.html] and then sorting the tach signal separately.
I am also looking at this 200amp unit.. but they include an "overdrive pulley" out of the box.. which means they don't know shite about pre-GEMs rovers and their alternator tach signal...
www.powerbastards.com
Have any of you dealt with PowerBastards before? Their alternators are all new parts (housing as well)... so it looks interesting (though VERY EXPENSIVE).
200A High Output Alternator for Land Rover Discovery, 1994 - 1995 3.9L V8 - 13725-200-HD1-1 | PowerBastards.com | PowerBastards.com
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www.powerbastards.com
Have any of you dealt with PowerBastards before? Their alternators are all new parts (housing as well)... so it looks interesting (though VERY EXPENSIVE).
German Gruner
Well-known member
Hi, there is MF1 that cuts alternator charge to the battery.
The best way to destroy an alternator is by cutting connections when running. Alternator has coils that have an inductive load. When you cut connection, current they generate cannot find an outlet except through "puncturing" one of its rectifier diodes on alternator board. In fact, it is typical way for it to break. For example when brushes wear out and charge is interrupted suddenly, or when ground connection is cut. I would advise never doing tests like the one Discoclay are describing.
Regards
The best way to destroy an alternator is by cutting connections when running. Alternator has coils that have an inductive load. When you cut connection, current they generate cannot find an outlet except through "puncturing" one of its rectifier diodes on alternator board. In fact, it is typical way for it to break. For example when brushes wear out and charge is interrupted suddenly, or when ground connection is cut. I would advise never doing tests like the one Discoclay are describing.
Regards
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German Gruner
Well-known member
I am seriously considering adding a second alternator where my power steering pump used to be :_)
German Gruner
Well-known member
Ah. Yeah, newer engine management systems can be a little sensitive to that method.
If you put enough draw (load) on it (pre-OBDII stuff) it is generally fine. But you're right and I am duly chastised, thanks :-D
Well, my used alternator with new regulator is discharging 24/7. So...as per [someone up there^] I capitulated and bought a cheapo new alternator.. it will be here tomorrow. Once this is sorted I will be adding a second alternator, per prior comments, where the power steering pump used to be. I think I can get an identical stocker to fit, and I may try to fit a later 150a model or a delco 1-wire. I will create a new/separate thread for that, when the time comes.
It will look roughly like this (it's leaning forward because it's just pressed against the head with a plastic wrapper):
It will look roughly like this (it's leaning forward because it's just pressed against the head with a plastic wrapper):
