Battery light when cold.

Battery light when cold.

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Discussion

techspy

Original Poster:

321 posts

251 months

Saturday 9th October 2004
quotequote all
Hi All,
Recently I have been having my battery light stay on 10-30 seconds after starting up. It only happens when the engine is cold. Usually after sitting over night or for several hours is when this happens. I can rev the engine and the light will get dimmer. It doesn't come back on throughout the rest of the day and seemed to start this once the weather has gotten cooler.

Any ideas?

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

lotusguy

1,798 posts

256 months

Saturday 9th October 2004
quotequote all
John,

Sounds as if your battery is going away. How old is it? if three or more years, consider replacement. A battery will, over time, develop sulphide crystals (due to a breakdown of the Sulphuric Acid - H2SO4) on the lead plates in the battery which effectively reduce the amount of surface area the plates have, this reduces the amount of chemical reaction which can take place needed to accumulate and store energy.

Also, if the battery has ever been run down it's ability to hold a charge has been severly compromised - (independent studies have shown a battery's future storage capacity drops by 15%-20% each time it is run down). To be certain, take the battery to a Sears store and have it load tested for free.

Also, you want to rule out your charging system. with the car running, test the voltage across the battery terminals with a multimeter. You should see about 13.6VDC at idle. If so, it's most likely the battery, if not, check all your cable leads to be sure they are not corroded or loose. Take the appropriate remedies if these are found.
Happy Motoring! ...Jim'85TE

techspy said:
Hi All,
Recently I have been having my battery light stay on 10-30 seconds after starting up. It only happens when the engine is cold. Usually after sitting over night or for several hours is when this happens. I can rev the engine and the light will get dimmer. It doesn't come back on throughout the rest of the day and seemed to start this once the weather has gotten cooler.

Any ideas?

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

quiksilver

26 posts

239 months

Saturday 9th October 2004
quotequote all
I'd get the charging circuit / alternator checked over.

techspy

Original Poster:

321 posts

251 months

Saturday 9th October 2004
quotequote all
Thanks fo the info Jim. I should have added that I have a new battery (sealed Optima type). I checked the voltage engine off and got right at 12v. I started the engine and for about 10 sec the battery light was on and the voltage dropped to just about 11.5 volts. When the battery light went off the voltage went up to just about 13.5 volts. So its obvious that the alternator isn't charging for those first few seconds after starting up.

So do you think the alternator needs rebuilding or could it be that the regulator needs replacement? I have taken the alternator off an 83 Turbo before and I am not looking forward to that challenge again. I will check all the connetions just to be sure that isn't the cause.

John
94 S4

lotusguy

1,798 posts

256 months

Saturday 9th October 2004
quotequote all
techspy said:
Thanks fo the info Jim. I should have added that I have a new battery (sealed Optima type). I checked the voltage engine off and got right at 12v. I started the engine and for about 10 sec the battery light was on and the voltage dropped to just about 11.5 volts. When the battery light went off the voltage went up to just about 13.5 volts. So its obvious that the alternator isn't charging for those first few seconds after starting up.

So do you think the alternator needs rebuilding or could it be that the regulator needs replacement? I have taken the alternator off an 83 Turbo before and I am not looking forward to that challenge again. I will check all the connetions just to be sure that isn't the cause.

John
94 S4


John,

Well, it could be the alternator, which has an itegral regulator. But, first check the obvious, such as the belt, connections, chassis ground etc.
Happy Motoring! ...Jim'85TE

sanj

225 posts

281 months

Sunday 10th October 2004
quotequote all
techspy said:
I have taken the alternator off an 83 Turbo before and I am not looking forward to that challenge again.


Not nearly as bad a job on your '94, I just changed the alternator in my SE the other day in well under two hours. Biggest problem was moving the catch tank I had installed out of the way.

Cheers,
Sanj

lotusman

124 posts

262 months

Sunday 10th October 2004
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I do not know what brand alternator is in your '94. I have a Valeo. Since I owned the car in 1996 I have needed the alternator rebuilt when the goo in the voltage regulator melted and dropped into the brushes. I have put two more voltage regulators on since then when they gave out. Simple job. Take out alternator, unscrew the voltage regulator, replace with new regulator and reinstall. Better to have a good auto electric shop( I called four before I found one that knew a Valeo alternator was not some piece of workout equipment) do it once to show you how. About $140 for part and rebuild. A new alternator costs about $600. A new regulator costs $35.

Good luck,
lotusman
'89 non-SE

techspy

Original Poster:

321 posts

251 months

Sunday 10th October 2004
quotequote all
From what I remember one of the bolts was really hard to get out. I believe I had to remove something else that was in the way to get it off.
I am hoping that it just needs the regulator. I will take it to an auto electric shop to check out completly though. It really has me puzzled that it seems to be heat related. Meaning that when it warms up, it works fine. It only happens after a cold startup (for now).
I would like to get the part number for the regulator and have it in hand so I can just pull the alternator, replace the regulator and reinstall.
Does anyone know what parts, other than the regulator, could be going bad? How about a part number for the regulator? I will double check the connections to make sure everything is secure. There should only be 2 wires right? One main one for charging and one for the gauge/idiot light right? It grounds through the bracket right?

Thanks

John
94 S4

Esprit2

279 posts

236 months

Monday 11th October 2004
quotequote all
techspy said:
Recently I have been having my battery light stay on 10-30 seconds after starting up. It only happens when the engine is cold. Usually after sitting over night or for several hours is when this happens. I can rev the engine and the light will get dimmer. It doesn't come back on throughout the rest of the day and seemed to start this once the weather has gotten cooler.



John,
Alternators are self-energizing once they get going. However, they don't hold much residual magnetism and need a small priming current to get them started. The charge light circuit provides that current. When the alternator's output finally comes up, the light goes out.

The light doesn't indicate battery condition, but it will tell you the alternator is giving up. If it's the original Valeo, replace it with a Bosch AL49X. It was used on some Audis and BMW's. The Bosch unit from a Merkur Scorpio will also bolt in. Pull your alternator and take it to an auto electric shop for a nice chat with the counter-guy.

Good luck,
Tim Engel
Lotus Owners Oftha North

>> Edited by Esprit2 on Monday 11th October 05:39

techspy

Original Poster:

321 posts

251 months

Monday 11th October 2004
quotequote all
Well, I ordered a new regulator from JAE. It's only $25, and I may be able to replace it without pulling the alternator. I will report back with the results.

John
94 S4

techspy

Original Poster:

321 posts

251 months

Friday 22nd October 2004
quotequote all
Well, I replaced the regulator and it made no difference. So I took it to a local alternator repair shop and they had it back in 2 hours with a new rectifier, new brushes and brush holder, and new bushings and gave me a lifetime warranty. They didn't have the rectifier on hand so he rebuilt the original. All for $80! Working like a champ now.

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

wcdeane

210 posts

261 months

Friday 22nd October 2004
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John: I had the exact same symptoms a few months back. It finally left me stranded on the highway on the way to work. It turned out to indeed be the alternator. I found a local outfit that would rebuild mine, and unfortunately I never inquired with the tech as to the exact cause. However, I do remember noticing a black compartment on the back of the housing that was noticeably heat stressed. The good news is that the rebuild set me back only $75 UDS and I haven't had any problems since. In fact, the car has never run better. I guess a healthy charging system can make a performance difference too...I made that equation, anyway

Walt...'91 SE

Esprit2

279 posts

236 months

Friday 22nd October 2004
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When an alternator dies, it's typically the rectifier diodes that fry first. And they do get hot, hence the heat discoloration.

You can just replace the diodes or the complete rectifier bridge and fix the problem. But by the time the diodes fry the bearings are usually old enough for a full rebuild to be the wise thing to do. The bearings are cheap.

Regards,
Tim Engel
Lotus Owners Oftha North

techspy

Original Poster:

321 posts

251 months

Saturday 23rd October 2004
quotequote all
Yeah that black housing is the rectifier and he did ask if the alternator was getting hot quickly, like after 5 minutes. So that was the prob. I did tempt fate with mine as I drove it for a good 2 weeks with the problem hoping it wouldn't leave me on the side of the road.

John
94 S4
http://hometown.aol.com/oneshotcop/myhomepage/profile.html

techspy

Original Poster:

321 posts

251 months

Monday 27th June 2016
quotequote all
Just an update for anyone else with alternator issues. Mine went out again (12 years since the rebuild) and this time I went with the 14812 from OReillys. It was $90 after the core return. I rotated the basket to get the wire connections closer to the OEM. The bolts were phillips head screws and very hard to get off. One stripped so I had to slot it. Then when putting them back on, one broke. Hopefully 3 is enough!