Over the past few weeks I've noticed that my battery light stays on unless I rev it past 2500rpm, then it's fine throughout the day unless the car is parked up all day. Three years ago I had a similar issue but then the light would stay on, but dim sllightly at high revs. It was suggested that the regulator was at fault but the alternator fitted to my car is unusual in that it isn't the same as any that I've seen at the scrappers or online. I managed to get a used one on ebay at the time that actually was the same type, but I can't find one now.

 

The belt seems good, doesn't audibly slip or squeak and I've cleaned up all the contacts on the battery, alternator. Any ideas chaps?

My immediate thought when someone says something like your subject line is "regulator" (aka control box). Also, with a Felly you have 2 possible fail modes, one of which causes low charge, and the other of which causes high charge (which is worse, since it can boil your battery and/or fry the electronics).

Hi Ken

I'm not gettting notified of any replies it seems?

I was just trawling the net and found my own post from back in 2011 when the first issue arose! http://www.briskoda.net/forums/topic/201712-battery-light-on-felicia-13/

It's not the same this time, it's completely the opposite, but still the regulator then?

 

I can't remember what the issue was regarding the non compatibility of any the available regulators with my alternator, so will have to do some homework.........

Edited 4 August, 20169 yr by myjalopy

I managed to find the alternator part number so I'm going to put it here as a filing system for my future reference, that's all.

 

DELCO REMY DRA4153 (443113516631)  as fitted.    (Possible number for regulator is 443930134541 as on Woods Auto Supplies site)

Descripition:

Voltage [V]: 12

Alternator Charge Current [A]: 90

Plug Type ID: PLUG382

Length 1/ Length 2 [mm]: 14.0 / 60.0

Number of Ribs: 6

 

Cross ref:

SKODA 441040032266

SPIDAN 6053

HELLA 8EL737896001

LUCAS ...LRB00511

BOSCH 0986049390

QUINTO...9090120

 

Edited 4 August, 20169 yr by myjalopy

Before jumping to any conclusion, do the following voltage measurements:

• voltage on the battery at idle
• voltage on thick terminal of the alternator (B+) at idle
• voltage on the battery at 2500 rpm
• voltage on thick terminal of the alternator (B+) at 2500 rpm

Prerequisites:

Battery is still operational (how old is yours?)

Good connections on battery poles, ground connection, thick cable between battery and alternator. Better remove all connections to alternator and clean them well (remove negative cable of the battery first)

Hi Ricardo

 

I will check this out today, but my multimeter wires need replacing. I've already removed/cleaned all connections. Battery is 6 years old or so, but as these cars are not laden with gadgets (unlike my Jag), the battery is still good. For an old car, it constantly impresses me and others with it's ability to keep going.

 

I took the old regulator off last night and the pick ups are rather worn, so it's possible that revving the engine improves the contact?

Battery (ignition OFF) 12.03v

 

Battery voltage idle     13.36v

Alternator B+ voltage  13.4v

 

Battery voltage 2500rpm           13.4v

Alternator B+ voltage 2500rpm 13.43v

 

Since removiing/replacing the old regulator, the battery light doesn't stay on now. I'll order a new regulator off ebay, but not 100% sure it is the same ( looks the same, but mine has 14v stamped on it and the one on ebay is described as being 12v)

Battery (ignition OFF) 12.03v

 

Battery voltage idle     13.36v

Alternator B+ voltage  13.4v

 

Battery voltage 2500rpm           13.4v

Alternator B+ voltage 2500rpm 13.43v

 

Since removiing/replacing the old regulator, the battery light doesn't stay on now. I'll order a new regulator off ebay, but not 100% sure it is the same ( looks the same, but mine has 14v stamped on it and the one on ebay is described as being 12v)

Battery itself is good.

 

I normally get somewhere between 14 and 14.4v engine running and heavy electrics off though (variety of makes and models).

Hi Ken

I've asked the ebay selller about the 14v/12v issue, but no reply. I'm assuming that it means that the regulator will cope with up to 14v, like you mention you get on your car?

The reason for the "variety of makes and models" note was that. while I couldn't state exact alternator types, I know I've tested AC Delco, Bosch, Ducillier and Lucas units, and may have tested Magnetti Marelli and others too. Exact details of fitting and output amperage may vary but alternators usually work the same way, to the extent that you might find 2 or 3 makes and a variety of output power on the same car model depending on electrics.

The battery

A 6 years old battery is 95% dead. Not only it doesn't hold charge well but its internal resistance goes up. Apparently the battery looks still good but it will die very soon, abruptly. I had a Bosch battery that lasted 6 years too.

 

The voltage regulator

Minimum length of carbon brushes is 5 mm. If you still think the voltage regulator is bad (and not the battery) buy one for 90A that matches the alternator. All car voltage regulators are rated 14V but the important feature is the maximum current of the alternator (90A in your case).

Edited 5 August, 20169 yr by RicardoM

In fact you said the battery light stays on for a while then it goes off all day so long as the engine runs. To me that is further proof the battery is too old. After it gets a little charged, the lights goes off. Next day the battery is flat again because it doesn't hold the charge anymore.

 

I don't see any scenario where the voltage regulator is bad in the morning, good after a little while then bad again next morning. More proof to that is the voltage measured on battery/alternator which is constant (13.4 V) but too low. Normal voltage without any load is like Ken said (14 - 14.5 V). It's not the fault of the voltage regulator, it's the internal resistance of the battery that got too high from age.

That battery is only around 50% charged up if showing 12.03V unloaded, see something like this chart.  That suggests to me that it isn't getting enough juice from the alternator, and at 13.4V that's not surprising. Is there a friend who would lend you their (known good, youngish, fully charged, 12.5V-plus) battery to temporarily fit into your car and see then what the voltage is when running? I suspect you will still see low voltages, but it will help to show one way or the other whether the alternator is underperforming. 

 

14.2V +/- 0.2 is a good ballpark for an alternator output, they are only nominally 12V as opposed to 24V for a truck charging system.  Any voltage regulator that only put out 12.0V would fail badly at charging the battery.

Hi Chaps

A lot of good advice here, not sure about 5mm for the maximum length of the brushes, they are more like 10mm now. I can borrow a battery, so will go from there.

It is odd that since re-seating the regulator, the issue has not returned.

5mm is the minimum length, not maximum, have another look at what Ricardo wrote. Good news that you can borrow a battery.

 

A poor earth connection on the voltage regulator can cause low output, this is sometimes made via a mechanical mounting (screw), so just removing/refitting the regulator might have cleaned/improved the connection. Has the output voltage gone up?

Edited 5 August, 20169 yr by Wino

That battery is only around 50% charged up if showing 12.03V unloaded

Very true according to that table but old batteries don't play that nice and die slowly in a linear fashion. In real life 6 yo batteries rather die suddenly one day out of the blue. Even if the alternator / voltage regulator prove to be bad (which I doubt) the battery should go to the heaven of batteries because a bad battery can potentially kill in turn the alternator.

Very true according to that table but old batteries don't play that nice and die slowly in a linear fashion. In real life 6 yo batteries rather die suddenly one day out of the blue. Even if the alternator / voltage regulator prove to be bad (which I doubt) the battery should go to the heaven of batteries because a bad battery can potentially kill in turn the alternator.

 

I don't understand how a bad battery can make the alternator put out current at a lower than normal voltage unless the battery is drawing a rather large charging current (more than the alt can supply at given rpm and regulated voltage). The fact that the output voltage hardly improves at all between idle and 2500rpm (when its current output capability will be significantly higher) suggests that this isn't the case?

 

Hopefully the borrowed battery experiment will shed light on the situation.

Edited 5 August, 20169 yr by Wino

I don't understand how a bad battery can make the alternator put out current at a lower than normal voltage unless the battery is drawing a rather large charging current (more than the alt can supply at given rpm and regulated voltage). The fact that the output voltage hardly improves at all between idle and 2500rpm (when its current output capability will be significantly higher) suggests that this isn't the case?

Again, an old battery could fail in two ways:

• The internal resistance of the battery gets higher and higher due to electrochemical factors . The voltage regulator in turn lowers the charging current resulting in lower voltage on battery.
• The spent active material settle as sediments at the bottom of the battery case and could cause a short circuit between the plates. The battery acts as a quasi-short for the alternator, the charging current turns to heat and the battery is not charged enough. Again, we get a lower voltage on battery.

Moreover, a weak battery could prevent the charging voltage from reaching the voltage regulator cutoff point. This lower voltage could be interpreted as indicating a defective alternator and/or voltage regulator. If the vehicle continues to operate with low system voltage, the stator winding in the alternator can be overheated, causing alternator failure.

 

Edited 6 August, 20169 yr by myjalopy

Not got the borrowed battery yet, but will report back when I do. ( I re-read Ricardos post, he did say 5mm minimum carbon brush, so I must use my glasses more often!)

It is odd that since re-seating the regulator, the issue has not returned.

Unfortunately it will. By reducing the contact resistance, the alternator charges a little bit better a dying battery and the battery light is not on. But it will be soon. You have just bought a little more time. I still recommend a new battery because forcing your luck might kill the alternator too. Just as a suggestion, I am using a Bosch S3 56Ah battery.

The OP should re-measure the charging (engine running) voltage, if the fault has not returned.

If it's improved significantly from the 13.4V, the battery should start to show better off-load voltages within days (assuming the car gets some use, and not all on super-short journeys).

Edited 7 August, 20169 yr by Wino

Agree. Even better, a decent garage has a battery load tester that can assess in a matter of minutes the real health of the battery. If the 6 yo battery has been used on an almost daily basis and still has the ability to crank the engine after the car has been sitting for 1-2 days, I want one too. Call also the Guinness Book of Records

The OP should re-measure the charging (engine running) voltage, if the fault has not returned.

If it's improved significantly from the 13.4V, the battery should start to show better off-load voltages within days (assuming the car gets some use, and not all on super-short journeys).

 

 

If the 6 yo battery has been used on an almost daily basis and still has the ability to crank the engine after the car has been sitting for 1-2 days, I want one too. Call also the Guinness Book of Records

 

Hi chaps

The borrowed battery plan isn't going to happen soon, so I may just buy another one (£35 to £90, depending on where/what you buy). The measured voltage hasn't changed since re-seating the regulator, but the car hasn't been driven, just started.

 

Ricardo, I'll be calling the GBR because not only does the battery crank and start the engine after a typically 4 day break ( my shift pattern) but it does so with gusto, usually iin the cold at 5am. When I buy my new battery, I can ship the old one to you for, say.....£150?

On the subject of batteries, you are using The Bosch S3 56Ah one, which is £76 in the UK. Most websites give a 40Ah battery as the main option for my car, so the cold cranking is 340 compared to 480 on yours. I presume that 'the higher the better'?

Please check the charging voltage once you have the new battery in place.  If it remains around 13.4V, which I expect it probably will, your new battery will soon be suffering from low state of charge (which is bad for car batteries).