www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums TDIFAQ Articles Links Meets
Orders TDI Club Cards TDIFest 2014 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You



Go Back   TDIClub Forums > VW TDI Discussion Areas > TDI 101

TDI 101 Got a simple/basic TDI question? Are you a newbie (new to the forums). Feel free to post your question here.

Reply
 
Thread Tools
Old October 31st, 2008, 08:09   #1
bw356911
Newbie
 
Join Date: Apr 2008
Location: Clifton Park, NY
Default Low or no voltage to exciter wire to new valeo 120amp alternator

When I start the car after charging a new battery and have installed a new 120 amp valeo alternator, the car charges at over 14 volts then the battery idiot light goes on and the voltage is below 12. There is at most 6.75 volts in the exciter wire then goes to zero with no voltage ever on the return side wire. The fuses are good on the fuse panel on the battery and I have lubed and checked all the wires to the alternator from the fuse panel on the battery. How do I get at least 12 volts to the exciter wire. There also seems to be some kind of drain on the battery as it will go dead overnight. A red light was blinking on the radio so I removed it but the problem still exists with the exciter wire. The car is a 2004 jetta 1.9 TDI A4. Thanks for the help.

Last edited by bw356911; October 31st, 2008 at 08:15.
bw356911 is offline   Reply With Quote
Old October 31st, 2008, 17:23   #2
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default Checking alternator wiring 2004 PD

I am confused by your post - I cannot figure out for sure which wires you are referring to.

Let's use some concrete terminology. Do you have a Bentley's manual? If not put it on your shopping/gift list. Connectors are named such as T32 for a 32 pin connector, and T32/3 means pin 3 of the 32 pin connector.

Clean the major grounds under the battery and in the ECM plenum. They must be clean.
Verify that T32/9 and T32/24 on the connector for the instrument cluster control module both have zero resistance to ground.

Verify the battery light comes on when you turn the key to on. This lamp must come on for the voltage regulator to work properly.

Verify fuses 11, 15, 22, 23, are not blown. Take them out and polish the conductors on the end. Then put them in and out several times to clean the clamping contacts.

There should be a blue wire coming in to the L terminal on your alternator. This wire comes from the indicating light on your dash, and supplies the field. This comes from pin 12 of T32 - the 32 pin terminal on your instrument cluster control module, via pin 2 of the T4 connector near the starter.

There should be a brown and red wire going to the DFM terminal on your alternator (Was this the "return" wire you were speaking of?), this wire feeds to and from the ECM via pin 1 of the T4 connector near the starter. The function of this wire is not well documented, but I think it allows the ECM to control the alternator. It sounds as if it is possible that the ECM or built in overvoltage system is turning off your Alternator due to an overvoltage condition. Exactly how high is the "over 14 volts" you are getting immediately after start up?

Check 1) verify that you have Battery voltage on the large connector on the back of the alternator, marked B+.
Check 2) Turn on your key and verify that terminal D+ on your key's electrical connector is at battery voltage.
Check 3) Verify fuse 11 has battery voltage on both sides of it, with the key on.
Check 4) start your car with the voltmeter hooked up on the B+ terminal of the alternator and the positive terminal of the battery. Try to catch this reading during the initial burst of alternator output. This is to verify that you don't have a high resistance contact somewhere in this path that is causing an overvoltage condition on the alternator.The closer this reading is to zero the better. If this is much over zero, clean all the contacts between B+ on the alternator and the battery positive terminal. This would include fuse S177(fuse 5 in the bracket above the battery), the common conductor to one end all five of these fuses, the large wire to the positive battery terminal, and the positive battery terminal itself. It sounds as if you have already tried to clean these, but this will check them. If you need to, you can hook up a jumper cable from the B+ connection on the alternator directly to the battery Plus terminal. Take great care not to short this to ground, or you will start your own arc welding class. If this jumper cable allows the system to work, it is a sign of a high resistance contact.

If all of these checks are good, then check for good conductors between T32/12 on the instrument cluster control module, and the L pin on the alternator. Make sure you do not have dirty contacts, check it for resistance to ground (should be infinite resistance when unplugged at both ends), check it for zero ohms resistance from end to end. You can insert a pin or needle into the wires near the ends (to give you another place to measure from rather than the end connections) to help you determine if there is a bad connector on one end or the other.

Perform the same checks for the brown and red wire from the DFM pin on the alternator to T94/pin64 on the ECM. This passes through T4/pin1 near the starter, and T10w(white) pin 5 in the ECM plenum connector protective housing on the left side. Check that it is not grounded and that it has low resistance from end to end.

This is quite a chunk of work. Hopefully it will surface the problem.

Dan

Last edited by DanG144; January 25th, 2009 at 15:53. Reason: more descriptive names for components
DanG144 is offline   Reply With Quote
Old November 1st, 2008, 06:19   #3
bw356911
Newbie
 
Join Date: Apr 2008
Location: Clifton Park, NY
Default

Thank you very much.
bw356911 is offline   Reply With Quote
Old November 1st, 2008, 09:13   #4
ymz
Veteran Member
 
Join Date: May 2003
Location: Between Toronto & Montreal
Fuel Economy: 5.3 l/100 km (at 115 km/h)
Default

Great Post, Dan !!!!!!!

Much appreciated.


Yuri.
ymz is online now   Reply With Quote
Old January 25th, 2009, 13:51   #5
moparmatty
Newbie
 
Join Date: Oct 2002
Location: Priceville, Ontario, Canada
Fuel Economy: 57 IMP/MPG
Default

Great post DanG144!

The problem I am having is that the alternator in my car won't charge unless you rev the engine up over 2000rpm when you first start the engine. Once you do this it sits there and charges at just over 14volts as it should. Speaking with the dealer, I was asked if the battery light is on when you first turn on the key, before starting the engine. It is not. I was informed that there must be a break in the wire between the alternator and the battery light in the instrument cluster. I have checked for continuity in the blue wire between the alternator and pin2 of the T4 connector near the starter and it is good, but now I want to check from there to pin 12 of the T32 connector at the instrument cluster. Will unplugging the T32 connector cause me any grief when trying to restart the car? Can I get this unplugged without removing the cluster?

With the battery light not coming on, should I be checking for something else other than this?

Thanks,
__________________
Matt Tebbutt
Priceville, ON

VAG-COM Equipped
TB Tools Equipped
moparmatty is offline   Reply With Quote
Old January 25th, 2009, 15:10   #6
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

Matt,
I do not have any experience plugging and unplugging the T32 to the instrument cluster. Sorry.

I would not expect any problem unplugging it, then plugging it back in prior to starting the car.

I will take another look at the Bentley for other potential problems.

Dan
DanG144 is offline   Reply With Quote
Old January 25th, 2009, 15:51   #7
DanG144
Veteran Member
 
Join Date: Aug 2007
Location: Chapin, South Carolina, USA
Default

The alternator cannot work properly if the lamp circuit is open; that is why checking the battery light coming on when the key is on was one of the early checks in the post above.

In addition to the fuses listed above, you might check fuse 15, which also feeds the instrument cluster. I listed all the fuses that could possibly be feeding the battery light in the instrument cluster. Only one of them really does, and I imagine it is 11 or 15, but I cannot be sure.

If the bulb or lamp assembly is bad, then you will have the same problem as if the wire was open. The sensing line for your primary voltage regulator is not sending any information. So check for an open bulb/diode or assembly.

There are probably failures possible inside the voltage regulator that can also cause the problem you are having.

That is about all I can come up with. I will try to remember (and find time) to try to look this up in the ErWin on line factory service manual next weekend.

Dan
DanG144 is offline   Reply With Quote
Old January 25th, 2009, 19:11   #8
moparmatty
Newbie
 
Join Date: Oct 2002
Location: Priceville, Ontario, Canada
Fuel Economy: 57 IMP/MPG
Default

Thanks Dan. I appreciate the help.

I checked all the fuses on the side of the dash for continuity and all check out good.

Does voltage flow from the instrument cluster through the battery lamp down to the alternator or does it flow from the alternator to the lamp?

Matt
__________________
Matt Tebbutt
Priceville, ON

VAG-COM Equipped
TB Tools Equipped
moparmatty is offline   Reply With Quote
Old January 25th, 2009, 19:45   #9
MOGolf
Veteran Member
 
MOGolf's Avatar
Default

Quote:
Originally Posted by bw356911
When I start the car after charging a new battery and have installed a new 120 amp valeo alternator, the car charges at over 14 volts then the battery idiot light goes on and the voltage is below 12. There is at most 6.75 volts in the exciter wire then goes to zero with no voltage ever on the return side wire. The fuses are good on the fuse panel on the battery and I have lubed and checked all the wires to the alternator from the fuse panel on the battery. How do I get at least 12 volts to the exciter wire. There also seems to be some kind of drain on the battery as it will go dead overnight. A red light was blinking on the radio so I removed it but the problem still exists with the exciter wire. The car is a 2004 jetta 1.9 TDI A4. Thanks for the help.
That LED on the radio indicates the alarm system is armed, and removal of the radio would sound off the alarm.

Were you replacing an original Valeo alternator?
Did you get the correct alternator for the TDI? Or did they slip you one meant for a gasser?
What part number is marked on the alternator?
MOGolf is offline   Reply With Quote
Old January 25th, 2009, 19:48   #10
MOGolf
Veteran Member
 
MOGolf's Avatar
Default

Quote:
Originally Posted by moparmatty
Great post DanG144!

The problem I am having is that the alternator in my car won't charge unless you rev the engine up over 2000rpm when you first start the engine. Once you do this it sits there and charges at just over 14volts as it should. Speaking with the dealer, I was asked if the battery light is on when you first turn on the key, before starting the engine. It is not. I was informed that there must be a break in the wire between the alternator and the battery light in the instrument cluster. I have checked for continuity in the blue wire between the alternator and pin2 of the T4 connector near the starter and it is good, but now I want to check from there to pin 12 of the T32 connector at the instrument cluster. Will unplugging the T32 connector cause me any grief when trying to restart the car? Can I get this unplugged without removing the cluster?

With the battery light not coming on, should I be checking for something else other than this?

Thanks,
Reads like defective diodes in the alternator.
MOGolf is offline   Reply With Quote
Old January 25th, 2009, 21:37   #11
Ski in NC
Veteran Member
 
Join Date: Jul 2008
Location: Wilmington, NC USA
Fuel Economy: 48-52 typical
Default

On many alternator systems, the initial current supplied to the rotor (the exciter circuit) comes from the dash alternator lamp. Once engine starts and alt starts making current, the lamp has 12v on each side so lamp goes out.

If it takes a good rev to make alt work, and it works fine after a good rev, the dash light circuit is suspect.

This is a generic arrangement and I don't know if it applies to the tdi. Mine still works so I have not messed with it.
__________________
2001 Jetta TDI 5sp Stock 201k mi
1981 Rabbit IDI 4sp Sold at 339k mi
1990 S-10 4.3 4wd 5sp 154k mi
1986 VW Pathfinder 1.6 45hp Marine 4700 Hrs
2001 Cummins 8.3 420hp Marine 1660Hrs..REFIT DONE!!
Ski in NC is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -7. The time now is 06:29.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2014, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2014
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
1996 - 2013, All Rights Reserved
Page generated in 0.17394 seconds with 9 queries
[Output: 102.00 Kb. compressed to 86.33 Kb. by saving 15.66 Kb. (15.36%)]