Mk4 TDI Battery/Electrical

Joined
Feb 27, 2017
Location
Victoria
TDI
2002 Golf TDI
I have a mysterious electrical issue with my 2002 tdi golf, 5-spd.
The battery is draining overnight. It's a new battery - not the factory model.
I completed a drain test on the battery with a multimeter and found a draw of 20mA. Yet the car will start at 12.7V and be down to 11.36V the next morning. The math doesn't make sense, unless there's an intermittent draw I'm not catching? Are there systems that can come on at varying times?

The battery in the car has an AH rating of 54, lower than the 80AH recommended by the dealer, but I don't understand why a diesel needs the larger amp hours if the draw is only 20mA. Our night-time temperatures are generally just above freezing this time of year.

The dealer recommended a new positive battery cable, and cleaning the grounds on the negative side, which we have done.
 

macoombi

Veteran Member
Joined
Mar 1, 2011
Location
Ottawa, Ontario, Canada
TDI
'02 Jetta TDI
20 mA shouldn't be killing it. There's something else going on.

When first got my car the battery was acting up and I pulled every fuse that I thought was unnecessary before finally realizing it was actually the battery and not a hidden drain.
 

Tdijarhead

Top Post Dawg
Joined
Nov 10, 2013
Location
Lawrenceville PA
TDI
2003 TDI Jetta Daughters Car, 2001 TDI Beetle, Wife’s car, 2005 Golf TDI Mine, all 5 spds
Does it have an aftermarket radio? If so start there.
 

oilhammer

Certified Volkswagen Nut & Vendor
Joined
Dec 11, 2001
Location
outside St Louis, MO
TDI
There are just too many to list....
First, put the correct battery in it. :rolleyes:

Second, search for the battery drain TSB for proper instructions on how to find parasitic losses on your car's electrical system. Common culprits are the door latches, which can be checked easily with a scan tool.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
Even a Mk4 Beetle requires a 72 AmpHr bettery, so your 54 is WAY too small.


Ideally, get an H7 /Group 94R, but at least an H6/ Group 48 battery.
 

BobnOH

not-a-mechanic
Joined
May 29, 2004
Location
central Ohio
TDI
New Beetle 2003 manual
All the above info is correct, diesels need more a$$ cause they need stronger crank.
That being said I was sold wrong battery on my first TDI, before joining TDI Club. Worked fine, but barely lasted 3 years.
IDK if 20mA is O.K. or not, here is a link to aforementioned TSB.
 

robm2

Active member
Joined
Jul 21, 2017
Location
Terrace, BC, Canada
TDI
2003 Jetta Wagon
You may have a bad alternator with a shorted diode. Check for current to the alternator when not running. Check the voltage on the battery with the car running, but check it on AC, not DC. If there is anything more than a few millivolts of AC, you have a problem.
 

Powder Hound

Top Post Dawg
Joined
Oct 25, 1999
Location
Under a Bridge, Crestview, FL, USA
TDI
'00 Golf 4dr White 5sp, '02 Jettachero 5sp, Wife's '03 NB Platinum Gray auto(!)
Even a Mk4 Beetle requires a 72 AmpHr [battery]...
They only put the smaller size in because there just isn't room for a larger one in a NB.

In general, a diesel requires substantial amperage to light up the glow plugs. Then on top of that, you have the difficulty of getting the high compression engine to start turning over. Throw cold oil that retards spinning and cold that reduces battery efficiency, and you have a recipe for a very large starting current requirement. And the battery has to supply that large current for more than just a few seconds. That's why you need a substantial battery for these TDIs.

You also need to drive it long enough that the alternator will be able to recharge the battery, but that's a different discussion.

The 20ma draw when idle (engine off, ECU in shutdown mode) is a good number. Your car should be able to sit for weeks like that and start easily, as in theory it would take 50 hours to consume 1 amp-hour. IN your case, I'd suspect the battery first, particularly if it starts at 12.7v then falls below 12v by the time it starts. Even if you charge it completely, a compromised battery won't hold the charge.

If the battery has been abused, such as having been completely drained multiple times, then they can start to sulfate and die on you. This is a process where the lead on the plates turns to lead sulfate and flakes off the plates. Lead always turns to lead sulfate when the battery discharges, but what is referred to is the extreme situation where the sulfate is in a sufficient thickness that it can no longer hold onto the rest of the lead in the plate. The sulfate collects at the bottom of the cell, and at that point, no matter what you do to recharge it, the plates will never come back up to their former performance level. Also, some brands are known to be weak anyway. (E.g. walmart (N)Everstart. Ask me how I know.) In the worst of these situations, the lead plates can recharge and plate lead across the plates, shorting out the cell. Obviously, this would kill the battery.

AGM (absorbent glass mat) batteries are supposedly more resistant to this type abuse, but there are huge arguments (on this forum, anyway) with no real concrete answer as to whether they can sustain operation in really cold weather (and on this forum, there probably never will be). I have a couple of them in my cars and really like them. There are several versions available, and they tend to be more expensive than comparable flood batteries. Mine happen to be made by the East Penn company, and are sold under the Duracell label at Sam's Club. This particular battery may not even be available in your area; this just happens to be what has worked and is working for me. Your results will (not 'may') vary.

Never trust a lightweight battery. The physics of the situation are that amperage requires lead and acid, and a lightweight battery can't give what it doesn't have. Period.

There are several batteries that will work, and I've made recommendations of my own. Other people will have their own pet solutions, so you'll need to see what you can get and do some research. Suffice it to say that you will need to look for a sufficient Ah rating, which is not easy to do in this country, unfortunately. Cranking amps, and cold cranking amps doesn't really tell you what you need to know since it is a mere instantaneous rating, not the one that you need after the glow cycle. Doing some research will pay off down the road.

Good luck in resolving this issue.

Cheers,

PH
 
Joined
Feb 27, 2017
Location
Victoria
TDI
2002 Golf TDI
Thank you everyone for the varied and thoughtful replies.

I've spent the last few days testing the car in the mornings without turning it on, and it's been consistently reading 12.5V - I'm hoping this rules out a bad diode on the alternator (which I've also been checking for warmth at varying times).

The dealer has quoted me $200 for the battery, but it looks like that may be the culprit. I might investigate the starter first, but I'm not sure how much of a hassle it is to get inside it. A youtube video I found makes it seem fairly straightforward procedure, but I know those can be famous last words!
 

Fahrvegnugen

Veteran Member
Joined
Jan 21, 2017
Location
Burlington Vt
TDI
01 golf 1.9 alh gls silver
If you’re ok with spending $200 I’d do that to rule it out and be sure it’s good. Otherwise it is hard to find 80 AH in USA. If $200 is not ok, I’d shop for H7 /Group 94R and call that good.
 

macoombi

Veteran Member
Joined
Mar 1, 2011
Location
Ottawa, Ontario, Canada
TDI
'02 Jetta TDI
The original poster is from Victoria, BC. They don't know what cold is there. Those glows plugs are barely coming on so he doesn't need to worry about having the wrong sized battery.

They only put the smaller size in because there just isn't room for a larger one in a NB.
In general, a diesel requires substantial amperage to light up the glow plugs. Then on top of that, you have the difficulty of getting the high compression engine to start turning over. Throw cold oil that retards spinning and cold that reduces battery efficiency, and you have a recipe for a very large starting current requirement. And the battery has to supply that large current for more than just a few seconds.
 

jayb79

Top Post Dawg
Joined
May 20, 2000
Location
Exeter,NH
You may have a bad alternator with a shorted diode. Check for current to the alternator when not running. Check the voltage on the battery with the car running, but check it on AC, not DC. If there is anything more than a few millivolts of AC, you have a problem.
I had this problem troubling me for almost a year before I figured out what it was. This can be an intermittent problem, I started carrying a 10mm nut driver so I could disconnect the alternator from the connection on the top of the battery so the battery wouldn't go dead.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
The original poster is from Victoria, BC. They don't know what cold is there. Those glows plugs are barely coming on so he doesn't need to worry about having the wrong sized battery.

Even if the glowplugs don't get used like you in ON, he still needs the correct battery for the same reasons.
 

STDOUBT

Veteran Member
Joined
Jul 30, 2007
Location
Portland, effing Oregon
TDI
dos jettas
Not exactly. The way I understand it from reading the old-timers here, is the coil light will go out sooner if the ambient temp is high enough, but the power draw and glow duration is the same no matter the temp. This means even in high summer, the startup still draws just as much juice as in the winter.
 

Skydvr

Veteran Member
Joined
Jun 29, 2016
Location
Western MA
TDI
2002 Jetta MkIV
I had this problem troubling me for almost a year before I figured out what it was. This can be an intermittent problem, I started carrying a 10mm nut driver so I could disconnect the alternator from the connection on the top of the battery so the battery wouldn't go dead.
Haha! I had the same thing going on, though not for that long. I thought it was a diode as robm2 stated, but it turns out it was actually the voltage regulator. Unfortunately I found out I hadn’t actually repaired the issue (after replacing the diodes) on the first night of a road trip with my nephews. Thankfully the first night camping wasn’t down some backroad in the middle of nowhere, miles from cell reception.

With the car off, pull all of the fusible link connections and check the current draw on each to see where the drain is coming from.

Powder Hound posted some good info about batteries. You’ll need to replace it after running it down multiple times and trying to start on a dead battery. You can probably get by with the weather warming up, but as soon as the cold weather hits again, you’ll have forgotten about needing a new battery and will be finding yourself stranded. You can smoke cables trying to start on a marginal half dead battery.

Try to get a battery from a parts shop that sells primarily to private repair shops, or even the dealer if you are near a decent one. The big chains sell garbage built to lower standards (even from big names, buying power lets the stores dictate manufacturing cost). The chains will warrantee and prorate batteries, but you’ll be replacing them more frequently after being stranded somewhere, and spend more in the long run.
 

scooperhsd

Top Post Dawg
Joined
Aug 19, 2003
Location
Kansas City KS
TDI
NB, 2000, RED(5 Speed conversion) 2015 Golf SE
Well and good, but I would still make sure the other stuff is OK while you're at it. After all, the car is a 2002 :)
 
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