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Topic: Alternator burning up (Read 2618 times) |
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tlundkvi
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Ex. Scorpio 2.9 24V -95
Posts: 909
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Alternator burning up
« on: Apr 2nd, 2010, 4:23am » |
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Hi all,
Had my alternator replaced with a new 1,5 years ago because of a rectifier problem so I never thought of having to care too much about it anymore.
But a few days ago a nasty smell started to come from the hood, which was (too late) located to the alternator. The backside of the alternator was close to completely melt down beyond salvation.
Now the interesting part, the cause for all this. The last thing one wants to do is replace them every oil change.
Some theories:
- PS fluid on the alternator: First thought of this, because of the smell, but the reservoir is at max where I left it after topping up a few months ago. No visual leak either.
- Problems with electricity around the alternator: Would kill an alternator surely, but there was no other issues than the smell and no charge.
- Short circuit inside the alternator: Likely, would cause it to burn/overheat and fail.
- Bearing failure: There has been some knocking on the alternator side, which could have been a bad pulley bearing as well. I thought of the cam chain tensioners, i have a full new set now. This cause tremendeous heat, in the chain reaction some insulators melt and short circuits the alternator.
Just my thoughts. I will get a refund on the parts warranty, I'm free to replace with anything I want. AAA-towingservice required towing to a garage, so I will have it done there.
Does anyone have experience with the alternator burning (not in flames though) up like this? My dad had a similar thing with his old Mazda 818 20 years ago, but he didn't investigate the cause too much. He just replaced the alternator.
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Jonnycab
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Former owner of 2.3 Ultima Facelift saloon
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Re: Alternator burning up
« Reply #1 on: Apr 4th, 2010, 2:01am » |
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Was it a new brand alternator or a recon ?....If it came from a parts shop then it's most likely a recon 
As with most recon stuff....steering racks etc...they only usually replace the parts that are faulty & rarely do a total strip down 
I once bought a recon alternator about ten years ago for a Mondeo I had & it lasted less than a week before the bearings seized & caused the drive belt to catch alight  .......No joke, it really was on fire !!!.... & I had to grab my fire extinguisher out of the boot & give it a squirt, which meant a new fire extinguisher, as well as another alternator 
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #2 on: Apr 4th, 2010, 11:14am » |
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on Apr 4th, 2010, 2:01am, Jonnycab wrote:Was it a new brand alternator or a recon ?....If it came from a parts shop then it's most likely a recon
As with most recon stuff....steering racks etc...they only usually replace the parts that are faulty & rarely do a total strip down
I once bought a recon alternator about ten years ago for a Mondeo I had & it lasted less than a week before the bearings seized & caused the drive belt to catch alight .......No joke, it really was on fire !!!.... & I had to grab my fire extinguisher out of the boot & give it a squirt, which meant a new fire extinguisher, as well as another alternator |
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This was new production, but the "real" manufacturer is not known. I specifically verified this before ordering. Cost me some 160 euros or so, a Bosch would have been 400 euros.
Johnny, you think it's more the bearings then? It hasn't seized up though.
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Jonnycab
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Former owner of 2.3 Ultima Facelift saloon
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Re: Alternator burning up
« Reply #3 on: Apr 5th, 2010, 1:33am » |
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Not really sure mate, I just recounted a story that I remember about a burning smell associated with alternator seizure, although the smell was burning rubber from the drive belt.
If you think the bearings might be at fault, then best thing to do is remove the drive belt & spin the alternator pulley wheel by hand.
It should spin freely & quietly......any resistance or grinding noises, then it's a bearing problem 
If the smell is electrical, then it's most likely something to do with the charging part of the alternator. If the battery light on the dash is lit, then the voltage regulator is the likely cause (Have you checked that the alternator is outputting between 13.8-14.4 volts ?).
But if the battery light isn't on, then it could be a diode burning out (may cause the battery light to illuminate very faintly).
Another thing....I recently had a horrible electrical burning smell from the alternator when the matrix inlet pipe burst just over the alternator & soaked it with about 4 litres of coolant. The smell was quite overwhelming & I was sure that the alternator was a goner. But the smell dissappeared once it had dried out, & it's still charging fine 
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tlundkvi
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Ex. Scorpio 2.9 24V -95
Posts: 909
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Re: Alternator burning up
« Reply #4 on: Apr 5th, 2010, 7:28am » |
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In my case though the rear of the alternator is virtually completely melt, and the smell is close to burnt rubber/oil/plastic. There is no charge at all, but the pulley is spinning. I'll post some pictures when I have replaced it.
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #5 on: Apr 6th, 2010, 7:25pm » |
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As promised, here's some pictures. To me, it looks like the rectifier pack started it all. Bearings are fine, considering the circumstances (no play):
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Scorpio_Mike
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Jeep Grand Cherokee 3.0 V6 & 2.8 Sierra XR4i 4x4
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Re: Alternator burning up
« Reply #6 on: Apr 6th, 2010, 9:15pm » |
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That looks well and truly cooked !
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Mike H
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Renault Clio
 
Posts: 2594
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Re: Alternator burning up
« Reply #7 on: Apr 20th, 2010, 1:59pm » |
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on Apr 6th, 2010, 7:25pm, tlundkvi wrote:As promised, here's some pictures. To me, it looks like the rectifier pack started it all. Bearings are fine, considering the circumstances (no play):
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That is truly bizarre. Definitely something went horribly wrong there!
Would just replacing the rectifier bit do? Though still need a reason
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Mike H
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Mike H
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Renault Clio
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Re: Alternator burning up
« Reply #8 on: Apr 21st, 2010, 12:09pm » |
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on Apr 2nd, 2010, 4:23am, tlundkvi wrote:| Had my alternator replaced with a new 1,5 years ago because of a rectifier problem |
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So I gather it's now melted its rectifiers twice, deffo something awry going on to do that, they don't melt down for no reason. If it were a short-circuit fault of some sort that's one helluva lot of current I'm guessing
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Mike H
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #9 on: Apr 21st, 2010, 12:59pm » |
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Mike, the previous one (when I bought the car) failed with the (typical) dim battery light and collapsed when I was trying the freshly installed stereo on the German Autobahn. With no visual damage. Then I didn't react quickly enough because I received 13.3-13.5V charge, the sudden load was what eventually caused it to fail.
This was a brand new replacement, worked perfectly fine until this. This one just suddenly started to smell burnt. Must admit I drove with it without reacting it was the alternator burning, but that was only for 50km during 2 days all together. 100A@14V makes 1400W, it's quite a lot.
I now again with the one currently installed (original Marelli, 44k KM driven from breaker yard) get a dim light. The battery is the same, 70Ah, gives 12.3-12.5V, the new alternator gives 13.7-13.8V (original spec says 14.0V) with lights, AC and radio. If I charge it overnight it becomes dim the second day. Either not enough charge or too little charge accepted  There's no remarkable drop when e.g. turning up the volume. Typically I drive 10km 3-4 times a day. Can the battery be on it's way, or may it have been damaged by this? I saw no signs of that before, even with the Finnish winter. It started fine even in -20 degrees C.
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tlundkvi
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Re: Alternator burning up
« Reply #10 on: Apr 22nd, 2010, 6:53am » |
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on Apr 21st, 2010, 3:36pm, Mike H wrote:
Dunno if it still applies here but a dim or twinkling warning lamp while running could suggest worn armature brushes. (?)
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The good thing is, if that's the problem, I have the regulator pack ready. Bought it in store when I had the problems 1.5 years ago.
Until now I had thought dim light meant worn diodes in the rectifier pack, but the weird thing is I get normal alternator output. Could still be, I will try to measure AC across the battery. Hopefully it's only because of the battery may not be 100% charged (it was drained). I took the car for a little longer spin yesterday and now the battery gives 13.1V with engine off. Lights were off this morning, but may come back
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #11 on: Apr 22nd, 2010, 5:20pm » |
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It's just weird, the alternator gives 13.8-13.9V with lights and AC off, battery 13.1V when I last measured. What do you mean exactly by main output, battery or unregulated?
The reason the one in the picture blew can't be much other than a short cirquit, amazingly it didn't damage the car (battery might have).
I'm gonna give the battery a go with a more powerful charger. Maybe it behaves better with absolute max charge.
Does anyone remember what the big UK-based alternator parts company was called , the one which had all parts online with full specs online (can't find it with google anymore) ?
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #12 on: Apr 23rd, 2010, 7:25am » |
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Now I found this:
http://www.alternatorparts.com/FAQ.htm#common_cause_of_failure
"You can tell your bridge rectifier is going bad when you first start a cold vehicle and it charges better at first compared to after it warms up. As the diodes in the bridge rectifier heat up they don't work as well. In high demand situations the more AC power the alternator makes, based on demand, the more power the rectifier has to convert to DC leading to a greater chance of diode failure."
Looks exactly like my issue. Seems it hasn't failed but is failing.
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martin_rowe
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Re: Alternator burning up
« Reply #14 on: Apr 23rd, 2010, 8:56am » |
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seems like alternator is over charging, probably a poor joint / connection between battery & alternator, reg senses low voltage, alternator provides full charge, no where for it to go.
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #15 on: Apr 24th, 2010, 9:39pm » |
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To summarize up the whole scenario so far with this case.
Today I drove some 140km with some shorter and longer stops.
First the dim light I have comes up after driving for 15-20 minutes, in one run, or in parts summed up without full cool down. I let it cool down fully and the dim light has gone away, until it's driven 15-20 min etc.
Charge voltage (or total system voltage) moves between 13.6-13.7V with dim light, 13.7-13.9V when without dim light. Battery voltage has never dropped below 12.8V when I've checked, after it was fully charged with a 12A charger, often it has been 13.1V, so apparently the alternator is charging at almost full rate. Battery was renewed by previous owner 3 months before me based on the warranty stamp on it.
When dim light goes on, it is unaffected (in intensity) by revs, and stays on for the rest of the trip.
Not affected at all by bumps, in either direction. Drove some pretty nasty rural roads with bumps and holes today as well. I have started to doubt the bad connection theory, for example the airbag light has in the past flickered more. The battery light has never flickered at all
I suspect a diode or two is unstable, as the heat/passed current seems to trigger it.
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Snoopy
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Re: Alternator burning up
« Reply #16 on: Apr 25th, 2010, 7:33am » |
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A dim light is usually symptomatic of a failing alternator diode in the rectifier. I had this on my Scorpio when I first got it. If the battery was a little low after starting the light would go out and after driving for a few miles and the battery was charged back up the dim light would come back on.
So I think your theory of a suspect diode would in my opinion be correct.
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tlundkvi
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Ex. Scorpio 2.9 24V -95
Posts: 909
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Re: Alternator burning up
« Reply #17 on: Apr 25th, 2010, 8:28am » |
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It's a shame though it needs to be taken off again, probably best to either replace all diodes (they should be of the stud types I guess) or get the whole bridge from Wood Auto if they answer my email.
Thank you all for the advice!
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #18 on: Apr 25th, 2010, 2:17pm » |
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Yepp, either the temperature does it or the electricity passing the diodes (=heat in a way too), causing a drop in efficiency. Probably measuring for AC during the dim light would verify this to fully.
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tlundkvi
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Ex. Scorpio 2.9 24V -95
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Re: Alternator burning up
« Reply #19 on: Apr 25th, 2010, 2:35pm » |
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Does anybody know, are these the studded type or button type rectifier diodes?
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