Relay 109 Engine Computer Power Supply

compu_85

Gadget Guy
Joined
Sep 29, 2003
Location
La Conner, WA
TDI
... None :S
This thread is a condensed version of the excellent Relay 109 information found in other threads on this site. The other threads have become long, and some of the links no longer work.



(images from schnabba)

What is it?
When you turn the key on in a TDI the relay marked 109 closes and supplies power to the engine computer and some other things. MOGolf provides a complete list of all the things powered by this relay here. All TDIs from 1996 to 2003 have this relay. In 2001 the design was updated and solved a lot of the problems.

What is the failure mode?
When this relay quits working the engine computer doesn't get power. If the engine computer isn't powered the engine will not run. The engine will simply crank and crank and crank. If the relay fails while the engine is running the engine will shut off just like you had turned off the key. When the key is turned the glow plug light will not come on and go out: The glow plug light coming on is the ECU's indication that it is powered up and working properly. If the connection only breaks for a moment you will feel the engine cut out, and see the glow plug light come on for a moment because the engine computer was just rebooted.

How do you fix it?
Replacement is the best method. You can get a replacement relay at many online vendors or at a VW parts counter. The part number is 1J0 906 381 A. The relay simply pulls out.

On the A3 and B4 cars (basically everything before 1999) the relay is located on the relay / fuse panel in the driver's footwell. Remove the trim piece above the pedals to access the relays. One mechanic mentioned some very early 1996 Passats have this relay in the center console area.


Picture of the CEII Fuse box found in the A3 and B4 cars (Courtesy of EtherNut) Relay 109 is the gray one which looks like 601

On the A4 cars (The new beetle and everything after 1999) the relay is located on the relay panel in the dash above the driver's footwell. The footwell trim needs to be removed for easy access. See this HOW TO.

Relay 109 is in position 12:

Image from tongsli


You can see the relay looking between the steering column and the dash trim.

Please note that a replacement relay may be a different color then your original, and the lettering may be upside down. Be sure to plug it in the same direction as the original one.

Why does it fail?
Some of the early relays have poor quality solder connections inside. The connections crack and intermentenly work. This is why sometimes waiting can get the car to restart. The contacts themselves can also go bad. The new, updated parts have larger contacts and better solder joints to prevent failures.

If this can cause the engine to stall, not start, etc, why wasn't it recalled?
Your guess is as good as mine...

Is there any way to prevent the failure of this relay?
As was already stated, VW fixed this problem quietly in 2001. The updated part is gray, and has 109 printed upside down relative to the older black units. The picture of the CEII fuse box above shows an OEM updated relay, the image of the original one fitted to my 99.5 shows one of the problematic ones. If you find your car has one of the original black units it would be a good idea to replace it for an updated one. The cost is very minimal and replacement is easy.

Note that some new aftermarket relays have a black case, even though they have the updated design.

-Jason
 
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maria_beetle

New member
Joined
Aug 4, 2008
Location
Festus, Missouri
TDI
2000 Beetle
Question?

The problem I'm having fits this (sort of). Last fall, I had problems starting my 2000 Beetl TDI. My husband replaced the glow plugs and harness wire. This fixed the problems I was having then. Recently, my car began having this problem:
Occaissionaly the glow plug light would not illuminate when turning the key to "on" and the car will not start. This was happening maybe once a month and only when my husband wasn't home to check it out. It started happening more frequently, but after letting the car sit for a while it would stat and be fine for several days/weeks. Now, the glow plug light is not coming on at all and the car will not start. We replaced the Glow Plug Relay tonight with no success. I've read the description of the 109 relay issue and it sounds like the thing to replace but another site said that this relay is either bad or good, no intermittant.
Has anyone has experience with this problem?
The car has over 180,000 miles on it.
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
The relay is either bad or good at one moment. The times it doesn't start it is 100% not good. The times it starts is 100% good.

Replace it.

Have you ever gone down the highway, typically in cruise, and have he cruise "cut out" for just a moment? Typically when it's hot?
Replace it.

gotta go gotta go 109... (repeat, sung to "getti-up getti-up 409..." ) Some may never heard that song. Sorry. Dating myself. It is 99.9% likely the problem.
 

egibbys

Veteran Member
Joined
Feb 20, 2008
Location
Salt Lake City, UT
TDI
1999 Jetta TDI GLS
rdkern said:
Have you ever gone down the highway, typically in cruise, and have he cruise "cut out" for just a moment? Typically when it's hot?
Replace it.
quote]

Thanks for that. I was wondering what was going on with my cruise control. I checked and I do have the old relay. Will be buying new one soon.
 

mrGutWrench

Top Post Dawg
Joined
Aug 29, 2002
Location
Carrboro, NC
TDI
'03 Jetta Wagon, 5-speed, 563K Miles (July '23)
maria_beetle said:
Thank you, I will see if I can get one today and get it replaced tonight.
I sure hope this fixes it, I love my Bug!!
__. Hey, MB, the new ones are much more reliable than the originals but they're still carrying a lot of load (electrically). What would be best would be for you to get two (they're reasonably inexpensive) and have somebody show you how to replace the one that's in there now and keep the extra in your glove box. Then, if you ever need to use the second one, you'll have it and you'll know how to do it.

__. It's a really easy job - you ought to know how; you only have to remove two parts, one by hand and one by using a "T-20" -- a kind of "star bit" screwdriver*. Once you have those two parts off (see the first post above and click the red link "See this HOW TO.", follow steps 43-46), you just pull the old 109 out and push the new one in. The new one will only go in one way - the right way. (Oh, yes, your car is what VW calls an "A4" body-model so don't get confused with the A3 instructions.)
(* You can get an inexpensive set of "T-Drivers" [a store clerk might call them Torx-drivers] at most auto-parts stores and "big box" places like da Wahmott and Tar-jay. You are likely to need them in the future and you'll be glad to have them. Just be sure that the set you get includes a T-20 -- it's commonly used anyway.)

__. And since the symptom of the "glow plug" light not coming on is such a tipoff, you'll know when it (if) it ever needs to be replaced again. Think of a spare 109 like a spare tire -- you hope you'll never need it but you'll be glad to have it if you do.
 
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TornadoRed

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Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
maria_beetle said:
Thank you everyone! It's been two days and this seems to have fixed my problem.

Maria
Welcome to TDI Club, Maria.

You folks in Missouri have a handful of top TDI pros (Oilhammer in the StL area, GT aka Glen Temple over by KC, Franko6 down by Joplin).

Maybe update your profile to show what part of the state you're in. And take the time to read as much as you can about your TDI, it will save you lots of worries and money in the future.
 

coner

Active member
Joined
Sep 8, 2004
Location
Ancaster, Ontario
TDI
2004 Jetta Reflex Silver
Can Relay 109 test ok but still be faulty?

About 3 weeks ago I had the car into the dealership for a no start (stalling) problem. http://forums.tdiclub.com/showthread.php?t=219890

The dealership replaced the 109 relay and said it was fixed. Fast forward 3 weeks later and now the car won't start!

When I turn the key to the run position I see all the dash lights illuminate except the glow plug light. I donesn't come on at all. After searching the forum I find this to be a typical sysmptom of a relay 109 failure.

I removed all the panels and got to the relay/fuse center. I removed the 109 and tested it by jumping the proper terminals. With no power applied, there is no circuit. With 12V power applied, the circuit is completed.

With the keys out of the ignition, I put the relay back into the holder and hear a click - as if the relay is closing. Is this normal (i.e should the relay complete the circuit as soon as I push it back in)?

Second question, even though the relay bench tested ok, is it possible it is still faulty?

My car is stick in my work parking lot which is a $200 tow from the dealership. They say to bring it in and they look at it and if the newly replaced relay (3 weeks old) is faulty they will replace it at no cost. Although it is still going to cost me the $200 tow to get it back there!

Any suggestions?

Thanks.
Eric
 

JB05

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Joined
Oct 20, 2005
Location
Il.USA
TDI
Golf,2005,anthracite blue
Stay away from the dealer and find a guru in your location where ever that may be.
 

TornadoRed

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Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
coner said:
Second question, even though the relay bench tested ok, is it possible it is still faulty?

My car is stick in my work parking lot which is a $200 tow from the dealership. They say to bring it in and they look at it and if the newly replaced relay (3 weeks old) is faulty they will replace it at no cost. Although it is still going to cost me the $200 tow to get it back there!

Any suggestions?
Considering that a Relay 109 is a $10 part online or $15 at a parts store or dealership, I would try replacing it again before calling a towtruck.
 

beetle98

Veteran Member
Joined
Apr 4, 2006
Location
Asheville, NC
TDI
99 Beetle TDi
So What next? My car has recently died a few times like key was turned off it started back. I have had a few starts where no glow plug light then eventually it would come on car would start and run fine. Now No glowplug light and no start. So i see this thread and replace the 109 relay with new relay from VW. One in car was already an upgraded relay i noticed. New relay same problem no start what do i try next? just a note I have a aux. fuel pump and normally when i turn key you can hear it come on for a few seconds then shut off until car is started. Now it comes on and just keeps running and no start.
 

DanG144

Top Post Dawg
Joined
Aug 2, 2007
Location
Chapin, South Carolina, USA
TDI
2005 A4 Jetta 5spd
beetle,
Why don't you post a new thread in the SouthEast section? Then come back here and post your new thread link. I am sure the guys around here can help you.
DanG
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
beetle98 said:
So What next? My car has recently died a few times like key was turned off it started back. I have had a few starts where no glow plug light then eventually it would come on car would start and run fine. Now No glowplug light and no start. So i see this thread and replace the 109 relay with new relay from VW. One in car was already an upgraded relay i noticed. New relay same problem no start what do i try next? just a note I have a aux. fuel pump and normally when i turn key you can hear it come on for a few seconds then shut off until car is started. Now it comes on and just keeps running and no start.
My guess? Grounds. Assuming one of the relay 109's is good, and this happens no matter which is in, a bad ground could cause the power not to get to the ecu. I don't know how your lift pump is wired - could be grounded differently.

I'd clean the grounds and see if it helps. If nothing else, it'll get you in the engine compartment, looking for loose wires.
 

maria_beetle

New member
Joined
Aug 4, 2008
Location
Festus, Missouri
TDI
2000 Beetle
TornadoRed said:
Welcome to TDI Club, Maria.

You folks in Missouri have a handful of top TDI pros (Oilhammer in the StL area, GT aka Glen Temple over by KC, Franko6 down by Joplin).

Maybe update your profile to show what part of the state you're in. And take the time to read as much as you can about your TDI, it will save you lots of worries and money in the future.
I will update my profile. So far, no more problems with my Bug. The 109 relay seems to have fixed my problem.
Thanks to everyone for the info.
 

moEras

Member
Joined
Nov 28, 2007
Location
San Diego, California
TDI
'00 Jetta TDI
Hi guys,
I've owned my TDI for 5 months and in 6 "rare" times it hasn't started... even the alarm/clock/everything were turned off (like if there was no battery) and sometimes it would come back later ON with no problems/

I am ordering the replacement 109 relay, does this look usual?

I drive a 2000 Jetta TDI 5 speed BTW.

Thanks,
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
moEras said:
Hi guys,
I've owned my TDI for 5 months and in 6 "rare" times it hasn't started... even the alarm/clock/everything were turned off (like if there was no battery) and sometimes it would come back later ON with no problems/

I am ordering the replacement 109 relay, does this look usual?

I drive a 2000 Jetta TDI 5 speed BTW.
The 2000 model year -- and those slightly older or slightly newer -- are the ones most vulnerable to the problem of relay 109 failure.

Even many of us with newer TDIs, which have a very low risk of failure, have decided it's better to have a spare in the glovebox, than to need one and not have it. Cheap insurance so you don't get stranded out in the boondocks.
 

nighthawk62

Veteran Member
Joined
May 22, 2008
Location
BANNED
TDI
BANNED
TornadoRed said:
The 2000 model year -- and those slightly older or slightly newer -- are the ones most vulnerable to the problem of relay 109 failure.

Even many of us with newer TDIs, which have a very low risk of failure, have decided it's better to have a spare in the glovebox, than to need one and not have it. Cheap insurance so you don't get stranded out in the boondocks.
Just curious but how much stuff do you have in your glovebox?:rolleyes:
 

TornadoRed

Top Post Dawg
Joined
Aug 3, 2003
Location
West Des Moines (formerly St Paul)
TDI
2003 Jetta TDI wagon, silver; 2003 Jetta TDI wagon, indigo blue; 2003 Golf GL 5-spd, red (PARTED); 2003 Golf GLS 5-spd, indigo blue (SOLD); 2003 Jetta TDI wagon, Candy White (SOLD)
nighthawk62 said:
Just curious but how much stuff do you have in your glovebox?:rolleyes:
Not much, actually. A couple H7 headlight bulbs, some taillight/brakelight bulbs, a relay 109, a bottle of aspirin, maybe a couple other small items.
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
moEras said:
Hi guys,
I've owned my TDI for 5 months and in 6 "rare" times it hasn't started... even the alarm/clock/everything were turned off (like if there was no battery) and sometimes it would come back later ON with no problems/

I am ordering the replacement 109 relay, does this look usual?

I drive a 2000 Jetta TDI 5 speed BTW.

Thanks,
This doesn't sound like a relay 109 problem. It generally doesn't affect the clock, etc. Sounds like a connection problem (bad ground, bad battery connection, etc).
 

moEras

Member
Joined
Nov 28, 2007
Location
San Diego, California
TDI
'00 Jetta TDI
rdkern said:
This doesn't sound like a relay 109 problem. It generally doesn't affect the clock, etc. Sounds like a connection problem (bad ground, bad battery connection, etc).
That's what I didn't know... but you know! I am replacing Relay 109 anyway. The battery terminal was in bad shape, I think I am going to replace it as well.

Thanks,
 

dr.diesle

Veteran Member
Joined
Mar 5, 2008
Location
Calgary
TDI
92 golf tdi/01 golf tdi /02 golf tdi/04 jetta wagon tdi/vanagon westy tdi
yes clean all positive / negative connections , make sure all are tight , you may need an ignition switch as well but further testing is required ..
 

rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
moEras said:
That's what I didn't know... but you know! I am replacing Relay 109 anyway. The battery terminal was in bad shape, I think I am going to replace it as well.

Thanks,
In my best estimate - 90% chance that the terminal is the problem.

Did you look under the terminal for the grounding points? That's sometimes surprising. Take those apart, and clean them.
 

PerkHouse

Veteran Member
Joined
May 9, 2006
Location
High Point, NC
TDI
2000 Jetta
another possibility

I can tell you from experience that relay 109 isn't the only cause of these symptoms. My y2k Jetta has been experiencing intermittent starting problems for a couple of months, but this morning it just wouldn't start. I checked all the usual culprits and even resoldered the connections inside the 109 relay, but the actual fix was to take the ignition switch (not the whole ignition, just the switch) out and clean/lube the contacts. For each contact, I sprayed some contact cleaner w/dialectric lube into it while holding it open with a small screwdriver. There is one normally open contact that closes when the key is fully inserted, so that one doesn't need to be held while spraying.

A word of warning to those who don't hold an electronics degree: You CANNOT use WD40 or any regular type of spray lube! You MUST use electrical contact cleaner (with or without lube). Normal lubricants will insulate the contacts and make your problem(s) even worse. A dialectric lube reduces oxydization of the metals in the contacts and actually (well, sort of) conducts electricity. Years ago, Radio Shack sold a contact cleaner. They might still have it. MCM Electronics is where I usually buy my chemicals though.

Oh, and I did notice one other symptom I didn't see mentioned by anyone else. When the key was turned to the on position, I could usually tell the car wouldn't start by the absence of the GP light, but sometimes it did illuminate. What was always true when the car failed to start was that all the other dash lights were about 2/3 the normal brightness. That might be hard to tell on a sunny day, but with all the cloudy days we've had lately, it was easy to see.
 

djoneil

New member
Joined
Feb 1, 2009
Location
Netherlands Antilles
TDI
2002 vw jetta
Help me please

vw bora 2002 the power windows does not work and the remote does not work to open the doors because the driver door does not getting any power.
 

TonyJetta

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Joined
Sep 15, 2005
Location
Tucson, Az
TDI
'15 Jetta TDI SE / '06 Jetta TDI DSG Pkg0 / '96 Passat TDI
Not sure what the problem is.

You may be better off starting your own thread under TDI101. You'll get more visibility where more people can help.

Tony
 

armedpolak

New member
Joined
Mar 17, 2009
Location
FL
TDI
2004 GTI
Same here!!! Is this relay 109 issue???

Hi!
I seam to be having the same problem with my 2004 VW GTI 1.8T.

It stalls at random when pulled to the red light/stop sign. It stalls when slowing down rapidly. It jerks when accelerating and car goes from 1st to 2nd gear. Sometimes, it takes 5-10 minutes to start the car back on. The power is there. Radio, etc. But turning the key does NOTHING.

When that happens ALL power is lost temporarly. Sometimes clock and milage resets.

Mechanic looked at the car and the computer gives no error codes. Cables, battery, all fine.

Could this be the evil relay 109 ???
If so, does autozone have it ???
 
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rdkern

Top Post Dawg
Joined
May 21, 2004
Location
Humboldt Co CA
TDI
Passat 1997 silver (sold after 11 years), Jetta 2000 atlantic blue
If turning the key does nothing - it isn't the relay 109. That relay has no impact on the starter motor, just the ecu and it's ability to control the squirting of the fuel.

Ignition switch is possible, bad ground, something other than the relay 109.

Might consider starting a separate thread. Your vehicle does have some problem, and more eyes on it would help.
 
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