Relay 109 - Main Power Supply Fuse

adamant628 · Jan 14, 2010

Can anyone tell me with certainty where by 109 relay must be located. I bought one a while ago to have for emergencies, but I've never actually located the relay. I didn't see any torx screws on the fuse panel (to the left of the dashboard, facing the door) to get behind that. Would it be under the steering wheel by the OBDII port?

Thanks

rbprintr · Jan 28, 2010

On my 2004 Jetta TDI (PD), I have been stalling occasionally in the first mile on a cold engine. After stalling, I'd have to crank the engine for several minutes before it would start again. When it happened, the car would sometimes stall up to three times before running properly, but would always be OK after the first mile. In that first mile, the engine seemed to be running roughly and surging. Keeping the revs up would prevent stalling, but if I let it go to idle, it would stall. The problem was happening mostly in cold weather, but I've had it happen once last summer. It's has been happening for the last 2 years, and I now have 61,800 miles on the odometer. After reading about problems with the 109 relay, I decided to try replacing mine. The dealer found a 103 relay (p/n 357 911 253) in position 12 rather than the 109 relay which, according to their books, should have been there. They put the correct one in, and I'm hopeful that solves the problem.

What is the difference between the 103 and 109 relays? Why would a bad relay cause this problem?

sempled · Jun 29, 2010

emergency fix

BRBarian said:
In addition to powering circuits on fuse locations; 32, 34, and 43, relay 109 also is connected to the unused fuse number 28.

So as an emergency road repair, you can jumper the fuse connector from fuse 12 to fuse 28 and bypass relay 109 altogether. Just pull the wire when you shut off your car...

Fuse 12 is the unswitched power source for DLC.

All you need is a short piece of wire with male fuse size pins at each end... If you don't have nice pins, you could probably just jam a wire into the fuse recepticles.

Quick and easy...

is this safe to do? My car is parked somewhere I'm not too happy with leaving it and until I source the part in Ireland i would like to bring it home. Can i do this, and will it cause any damage??
Where is fuse 28 i couldnt find it.
vw golf 1997 tdi

sempled · Jul 1, 2010

109- job done

Hi i got my new 109 today and low and behold it was grey, and slightly smaller. Got it home plugged it in and car started first time!!!!

thanks to this thread i only spent 18 euro on the relay rather than what i'm sure would have been at lot more had i gone to a garage.

ajrn · Oct 25, 2010

BRBarian said:
In addition to powering circuits on fuse locations; 32, 34, and 43, relay 109 also is connected to the unused fuse number 28.

So as an emergency road repair, you can jumper the fuse connector from fuse 12 to fuse 28 and bypass relay 109 altogether. Just pull the wire when you shut off your car...

Fuse 12 is the unswitched power source for DLC.

All you need is a short piece of wire with male fuse size pins at each end... If you don't have nice pins, you could probably just jam a wire into the fuse recepticles.

Quick and easy...

---will this work on my 97 B4 Passat???

I've ordered new 109's, but they're not here yet.. I just want to get the car home, so I can get other things done. I think I destroyed the one, that was there.. (I know-- dumb*%$)

shorty197 · Dec 1, 2010

TGOLF said:
Thanks Turbo for the post.
(New Member, but Fred TDI reader since '99)

I just replaced 109 relay and will get a spare. The replacement cured some of my problems that the Dealer won't / couldn't replace since May!
I have been on "109 relay" post so won't bore.

One other point on replacing the "...PT-109..." Relay.
Maybe my hands are to big, but I also remove with three screws the panel below the steering. Additional to the diagram MIGOLFGLSTDI shows.
Be careful as TurboSteve noted that the numbers on relays you pull or replace can be inverted. Speaks volumes to the quality...don't you think?
My pull of the 377 relay that Turbo notes was inverted and the new 109 relay went in inverted from original.

Anyway I find it interesting you note: ..."Failing ECM Load Reduction Power Relays have been known to damage ECU's when they go bad, not to mention the safety factor involved when they decide to die while you are idling in traffic or traveling on the highway!"...

I'm wondering if my ECU is now damaged. How can Dealer check if ECU is damaged?

Hi sorry for hijacking the thread, i have a 1998 A6 1.9tdi 110 i was driving home from work and my car cut out and has not started since i have checked for relay 109 i dont have this relay, you mention relay 377 i have that relay large black relay is this the old 109 relay pleas advise.
regards shorty.

1234567890 · Dec 8, 2010

gray or black?

I have seen that the new ones are black... then I hear they are gray... I have an 2002 Jetta with a gray one. I am assuming it is the factory one. Should I replace it? It reads 601 because it is in backwards. If I get a new one do I install it with the same orientation? I have 107000 miles on it.

For those of you having trouble locating it take the 3 torx screws out from under the dash above the pedals. Remove the plastic piece that is directly above the pedals. (I did not even remove mine just slid it toward the front of the car) If you place your head near the fun pedal and glance up looking to the drivers side you will see it tucked away above a larger relay.

TornadoRed · Dec 8, 2010

I keep a spare in my glove box, just in case.

sqhschief · Jan 4, 2011

I've never had a problem with mine. I'm trying to access my CCM for another mod and I'll check it while I'm in there. If I can figure out how to access the CCM...

DasTeknoViking · Jan 17, 2011

Stuck at home right now..... I have 2 spare relays that don't do me much good. Found them in the trunk of my car with a bunch of spare parts the PO gave me with it. One will not even make the car start, and the other one is doing the same thing as my original black relay : this is a B4 btw.

Does the jumping the fuses trick work on a B4 as underlined in a previous post few pages back ?

Either way, my relay gets hot.

DasTeknoViking · Jan 17, 2011

For you folks who also have gasser MKIVs.... I had this similar issue on my R32. Randomly the car would sputter out, and it always did this soon after starting it up. Ended up being the "409" relay. This controls the fuel pump in the trunk, not really familiar with the TDi MKIV so I can't tell if it has one or not, but Impex lists it for ALH powered cars too.
http://www.worldimpex.com/parts/genuine-part-fuel-pump-relay_162780.html
This could power your lift pump I guess.
I would carry a spare 409 also then, as I've seen quite a few of these fail on gassers.

Greeney · Feb 4, 2011

I have a Transporter T4 2003 was out the other day and the engine just cut while driving with no ignition lights
VW charged me 120€ to dismantle the Gemini alarm but I knew it would be the 109, after it was changed the vehicle was smoother running and started better too
I have only added to this because my faulty relay was GREY and replaced with another GREY one

mnlbj · Feb 26, 2011

needle lift sensor

i also need help,pllllleeeeaaassseeee, galaxy 1.9 tdi ahu,bought as spares or repair, fitted new engine & cam belt, now coming up with fault needle lift sensor, replaced injector 3 twice with a second hand injector,still the same checked & double checked timing, all ok, but still same fault & in limp mode,cut all wiring harness open to check wiring, all ok, could this fault be relay 109??????, im getting tired and need help,lol. car starts first turn but kicks lots of white smoke out and slow to rev up, any answers very much wecome,kind regards matt

sundownz · Mar 6, 2011

Is it safe to drive the car as long as it still runs with a suspected bad Relay 109 ? Simply to work and back - 5 miles each way in 45-55 mph speeds. Mine is on order but isn't due until Tuesday.

TornadoRed · Mar 6, 2011

sundownz said:
Is it safe to drive the car as long as it still runs with a suspected bad Relay 109 ? Simply to work and back - 5 miles each way in 45-55 mph speeds. Mine is on order but isn't due until Tuesday.

It is safe, unless the relay 109 fails totally while you're on the road and the engine dies in traffic. They are unpredictable. It would not matter whether you were driving 80 mph or idling at a light -- they either work or they don't and if they stop working then your engine will too.

sundownz · Mar 6, 2011

As long as it won't destroy the vehicle electronics -- that was my concern. Hopefully I make it to Tuesday without it breaking down!

coldfeet · May 24, 2011

my tdi golf has been shutting down for 4 years. here , there and everywhere. happened a couple of times on the triboro bridge nyc.

finally found this page after no GP light and no start.

relay 109er replaced yesterday.

started, lets hope no more shutdowns on the freeway.

kepsu · Jul 10, 2011

I've been having intermittent stalling or hiccup on the freeway. My car is a 1994 VW Golf tdi. It's like an abrupt total loss of power but lasts only like a split second. It almost never happens when engine is cold. Usually it starts after driving about ten miles or so. It's far more likely to occur at a steady speed than when accelerating. Cruise control stays on all the time, it does not drop off. Could this be caused by failing 109 relay? Or would it more likely be a faulty needle lift sensor?

TornadoRed · Jul 10, 2011

kepsu said:
I've been having intermittent stalling or hiccup on the freeway. My car is a 1994 VW Golf tdi. It's like an abrupt total loss of power but lasts only like a split second. It almost never happens when engine is cold. Usually it starts after driving about ten miles or so. It's far more likely to occur at a steady speed than when accelerating. Cruise control stays on all the time, it does not drop off. Could this be caused by failing 109 relay? Or would it more likely be a faulty needle lift sensor?

A new relay 109 is so cheap -- about $10 in the US, maybe a little more in Finland -- that you should probably go ahead and make the change and see if it helps. If not, then you have your old one as a spare for the future, and you've eliminated one possible cause of the problem.

kepsu · Jul 10, 2011

I will do that. I was just thinking that would a faulty relay also drop cruise control off...

TornadoRed · Jul 10, 2011

A faulty brake pedal sensor or clutch pedal sensor can cause the cruise control to drop off; and the brake pedal sensor could cause engine rpm to drop to idle.

kepsu · Jul 11, 2011

Maybe I've been unable to make my point. With the problem that I have cruise stays on. I meant to ask that would it not drop off if the cause was a faulty relay.

Vini · Dec 25, 2011

Hi TurboSteve you sound like a guru on TDI's, I have a 2005 Golf 2.0lt TDI I am having massive headaches as it will at times not start The prob is intermit when it goes its one crank and sweet when it doesnt it just wont fire as if there is no fuel source. I have fuel, air and I imgine heat for a start procedure in diesels. as per my post, I have checked just abot everything I can think of I have even had the car into the specialists and there is no fault coming up on the system and now getting to the point of thinking of selling the car and staying clear of TDI. If the dealer/specialist doesnt know what is at fault then who would. Strange thing is that when it does fail to start, I can start it by spraying earostart in the inlet. It will then chugger itself to an eventual start. As the fault is intermit/ I am automatically leaning towards an electrical fault with the ECU but again there is no fault showing up on the codes. I would imagine that if im my situation the 109 is at fault, I would not get a start even with the earostart or am I incorrect. Your and anyone elses help is appreciated. regards Vini.

mnorton · Jan 4, 2012

Luv My 02 TDI said:
I just replaced my 109 relay and took some photos of it on the inside.

The two large tabs at the top of the relay board show signs of overheating along with the solder joints looked cracked or like cold solder joints.
The left up solder joint is the back side of the contact area.

This is a I reduced in size and placed red lines on the cracks on the solder connections, They are hard to see. But if you use CTRL and + keys you can enlarge the view. If you click on it you should be able to see the Original LARGER size photo.

Links to all the photos.. Some with a flash some without.

Photo 1
Photo 2
Photo 3
Photo 4
Photo 5

Hopefully this will fix my problem, but I think it will.

There is lots of documentation about the black 109 relay however I've added a picture of an equally old off-white 109 relay. The soldering on the circuit board looks the same as the picture above.

It may be my imagination but the car seemed a touch more responsive after I installed the new gray relay.

Vini · Jan 19, 2012

MNORTON I would say it is probably just your imagination, you are right there is alot of documentation in relation to the 109 and its leading TDI owners in a field of misconception, a relay is like a light switch it either works or not it will not make any difference to the response of the car so all other fellow TDI's who have got starting or other problems don't all go out and buy a new relay thinking it will fix your problems

ropesca · Feb 4, 2012

TGOLF said:
Update since replacing the '109'.
I took my car back to clear codes and check what the Regional Rep. suggested to Dealer. They couldn't find any problems after clearing codes and didn't charge me the two hour labor they were going to.
Driven under all conditions which have brought on problems before replacement,have had no problems since install!

I asked Dealer if there was any way to check only the 109 relay. They didn't have an answer. (Dealer originally didn't know what a 109 relay was...601 may have helped)
Is there any way to check just the '109'?
I now have an extra '109', but I'm wondering if these newer 'gray 109's' are OK.
More importantly I would like some piece of mind that there isn't any other 'hidden' problems.

It seems to me from reading most of the 109 trouble is on cars with 2 years, 40K+, Maybe 109's should just be repleced at your 40K service...
I have petitioned with the NTSHA on 109 as saftey concern too.

I have both a black and gray 109 relay. I believe that both are good. If you check the resistance between terminal 30 (hot) and terminal 85 I got 59 Ohms with the black version and 150 Ohms with the gray one. This makes sense from previous threads that indicate that the black versions suffered from overheating, consistent with a lower resistance value. I have not checked the relay switched on.

jillybobs · Jun 13, 2012

Hi Guys,
I know this thread hasn't had any input for a while but I'm hoping there's someone out there who will catch it. I am no techie but am hoping you can help.
I have a 1.9 TDI 130 bhp right hand drive (English) Golf on an '04 plate.
It broke down (wouldn't start) miles from home while my OH was using it but fortunately the relative he was staying with knew a VW chap. The chap said it was a relay and he somehow short circuited it and hot wired it so my OH could get home. He said this would last a few weeks but we should get it replaced. My OH thinks he only got to this relay via the bonnet and didn't see him go inside the car.
From reading this post I think it may have been the main power relay that the chappie messed with but if it wasn't inside the car then where is it under the bonnet?
He said it would be about £480 to replace "it". Yikes!
(I have read a post on here about a Sharan which seemed to have this relay soldered to a main board. This would suggest that it would indeed be expensive to replace). Is this 109 sometimes part of a main board?
Few other things we had noticed about how the car was running before it actually broke down. It had a power surge or two occasionally. The dashboard lights would slightly flicker (dim and then come back full on).
From this thread it would seem that the 109 was not working properly.
A) Is the issue the 109?
B) Where on my model is it?
C) Is it part of a bigger circuit board so the whole thing has to be replaced?
Any help would be gratefully received.

whitedog · Jun 13, 2012

Did the glow plug light come on when you turned the key on? If not, this is a classic R109 sign.

Are the fuses on the drivers side of your dashboard? If so, then the R109 would be up above your knee.

The R109 is simply unplug and plug, not on a circuit board.

jillybobs · Jun 13, 2012

Hi Whitedog,
Thanks for your response.
I don't think my OH would have noticed/remembered whether the glowplug light was on or not as this happened a few weeks ago.
There is a fuse panel on the right side of the driver's seat cos I've been in there before for another issue we had.
When you say the 109 would be above my right knee. Is this got at from inside the car or under the bonnet?
Thanks,

whitedog · Jun 13, 2012

Inside the car.

What the Mechanic actually did, I have no idea, I was just commenting on the R109.

Relay 109 - Main Power Supply Fuse

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