A3 / B4 glow plug relay and fuse location

[Lug_Nut]

....i will follow the wire back from the 50 amp fuse on the fire wall, to the fuse box,....

well that is what someone said here, (about the fuse) however when i looked at it the wires didnt look right.
what IS the fuse on the firewall for anyways?

There are two fuses on the firewall.
The large strip fuse on the firewall, visible from under the hood, is the coolant heater fuse.
The fuse on the firewall, but on the INSIDE of the car, barely visible when the fuse and relay block is lowered, is the combustion chamber glow plug fuse.
Because you wrote "follow the wire back ..." I presumed that you meant the one under the hood. Had you written "follow the wire down... I'd have concluded that you had the correct fuse for this problem.
If I mis-interpreted your description of your plan of action, and came to an incorrect conclusion as to which fuse you were describing, I apologize.

 

[savannah996]

on the mk3 there are no fuses on the inside of the firewall. and we also do not have coolant heaters. i will look in my bentley on tuesday or wednesday and see what i was talking about. i do however have a 50 amp blade fuse on the top of my fuse box.

 

[Lug_Nut]

and we also do not have coolant heaters. i will look in my bentley on tuesday or wednesday and see what i was talking about.

You'll be able to correct the statement in your post, but this quote will be saved for posterity.

 

[rdkern]

You'll be able to correct the statement in your post, but this quote will be saved for posterity.

Can't get away with anything around here, can you?

 

[savannah996]

yet you are right, sorry i was ignorant without the bible!!!

 

[savannah996]

now if the bentley would just have the 1Z wiring diagrams i need to diagnose glow plugs and ecu.=fail

 

[TonyJetta]

1) Need a helper
2) Unplug glow plug harness from the GP's.
3) Unplug the Coolant Temp sensor (fools ECM into thinking the coolant is <30F)
4) Measure voltage at GP harness
5) Have helper turn key to ON
6) You should read 12V at all 4 connectors on harness.

If 12V not present, check for 12V at GP fuse under the dash.

If 12V present, check resistance of each GP.

If ambient temps are <35F GP's should be on (GP light) for about 2+ seconds. If the GP's are not on for long, I would bet the CTS needs to be replaced.

Tony

 

[compu_85]

on the mk3 there are no fuses on the inside of the firewall. and we also do not have coolant heaters. i will look in my bentley on tuesday or wednesday and see what i was talking about. i do however have a 50 amp blade fuse on the top of my fuse box.

Check again, unless for some reason VW didn't equip your southern car with coolant heaters... As far as I know every MK3 sold here has them.

-J

 

[savannah996]

check #65 ↑↑↑

 

[Lug_Nut]

yet you are right, sorry i was ignorant without the bible!!!

Check #64. We are all fallible.

The fuse on the firewall, but on the INSIDE of the car, barely visible when the fuse and relay block is lowered, is the combustion chamber glow plug fuse.

As pointed out, the fuse in the A3 is attached to the top of the relay block, not to the firewall as on the B4.
The B4 Bentley has the glow plug wiring schematics. My 1997 edition of the A3 does not have TDI schematics (not available at the time of printing).
I should have checked before buying that used manual...

 

[savannah996]

Check #64. We are all fallible.
As pointed out, the fuse in the A3 is attached to the top of the relay block, not to the firewall as on the B4.



..

correct, (for my A3 1Z)


my bentley for '93-99 A3's does not have 1Z wiring diagrams. when i called bentley they said "oh let me talk to my supervisor" came back and said "the ahu should be the same" haha let hope i dont short anything!!

 

[dieseljunkie]

.........
The fuse on the firewall, but on the INSIDE of the car, barely visible when the fuse and relay block is lowered, is the combustion chamber glow plug fuse..........

"barely visible when the fuse and relay block is lowered"

A crucial piece of information, not available till now!!!! I thought I was blind or mad or both, because for the life of me could not find the glow plug fuse. If only I had x-ray vision.

 

[Digital Corpus]

Broke down and bought a new 180 relay from idparts.com Not sure tif that description is for the B4's made in 97, but I wouldn't call the placement of the relay on the firewall. It's crammed way up top almost near the steering column on one of the 4 slots on the bracket that is hard to even see. I had to pop the relay off the bracket just to detach it and then used the socket mounted back on the bracket as something to push on to put the relay back in.

I already scoped out where the relay was last week. It still took me about 15 minutes to do the switch. If my check engine light comes back on, I swear I'm not going to be a happy camper.

 

[savannah996]

update on my issues=

my ecu and glow plug systems are working, there are just open circuits to the lights in the gauge cluster. AND the airbag ecu is not getting power, prolly also unplugged or something. wont be looking into it until monday i think. cant wait to see if its really that simple. my cruise control is not working iether, i think it is also not plugged up, so i will check that when i drop the fuse box also.

my last mpg=42 city.

 

[nuclear]

this thread is a moneysaver. I already burnt money on 97 relay when I have a 96. This solved the prob

 

[Metalnerd]

Many thanks guys for the usual teriffic technical support.
Your diagnostic details were a lifesaver (starter & battery saver too).
Mine ended up being a "tired" fuse. Not really blown, not corroded, just heat damaged or semi-melted somehow. I can't really complain after 14 years and 250K mi. of flawless glow controlling. I did replace the GPs in the past.
The dealer and europarts locals were out of stock but in a pinch, I found a Buss brand MaxiFuse that seems to work.
Any experience out there with the Buss brand in this applicaton?
An extra special thanks to VW for locating that fuse in such a handy location. That arm skin will grow back eventually.
Thanks again,
Chuck

 

[TonyJetta]

Chuck,
I have read about several people using a buss maxifuse and maxi-fuseholder to replace the OEM. IIRC, it all worked OK. Electrically, so long as the wire is properly sized, there should not be a problem.

Tony

 

[Metalnerd]

Thanks Tony.
The Buss MaxiFuse was a physically and Amperage drop-in replacement for 96 B4 type tucked to the underside of the dash. It must be the same format. I was just curious maybe that the durability might be worse/better since the original slowly cooked over the past 13+ years.

 

[redbeard]

My 98 Jetta began to have cold start issues a few weeks ago and thanks to this thread I was able to find the blown 50 amp glow plug fuse. Many thanks!

BTW - Releasing the plastic clips and dropping the fuse panel down makes this job much easier and saves arm skin.

Question: Why did this fuse blow? Just from old age or is there something else wrong? It always makes me a bit nervous to just replace a fuse and cross my fingers.

 

[TonyJetta]

Fuses are time-current devices. The more the circuit is used, the more likely they are going to blow. Also, it depends on how close the rating is to the actual current draw. Generally, the fuse should be rated ~15% more than nominal current draw.

Unless something is melted, I don't think you have a problem. IF the fuse blows again, it's time to look deeper.

Tony

 

[redbeard]

Sounds good. Thanks, Tony.

 

[TonyJetta]

You're welcome!

Tony

 

[timtenor]

Can anyone throw any light on this probklem?
Thanks for your knowledge info on the Golf TDI.
I have 1 1996 Golf TDI that will not start. I have replaced the relay 109 and all the dashboard lights (including glow plug light) now come on. The engine turns over freely and the battery is good, so, no starter motor problem.
From cold the only way to start the car is by bump starting it. So, far this has always worked. I have to park on a hill before I go to bed.
From warm the engine has to turn over for about 10 seconds before it will fire. It seems like much longer and is obviously not doing the starter motor much good.
Once running the car is very reliable - does not stall or stutter - runs perfectly normal, so, I am assuming that it is not a fuel problem.
I have located the air valve but on this model there is no black lever, just pipes. Is there any way to check that this valve is open, or force it to open, without removing it?
Any light that you can shed on this matter would be greatly appreciated.

Timothy Evans
Timtenor@web.de

 

[TonyJetta]

Timothy,
You would be better off starting your own thread. Basically a new post.

It sounds like either the glow plugs or injection timing, or both.

Use the following troubleshooting guide at your own risk!

1) Does the wait to start light come on (GP coil light on the dash indicators)? If not, I would suspect the coolant temp sensor - it has 2 circuits: 1 for the dash gauge and one for the ECU
2) Check glow plug resistance: All 4 should be ~<1 ohm If not, I would look into replacing them.
3) Also, notice how the harness feels when you unplug for #2; was it hard to unplug from each glow plug, or did it come off easy? If it came off easy, the terminal is probably not making good contact and the harness prabably needs to be replaced.
3) Check glow plug voltage at the harness, by removing the harness and check each terminal, with reference to ground. Older VW's should be approximately battery voltage
4) If one or more terminals are not giving proper output, replace the GP harness. If NONE of the terminals give proper output, check the Fuse and relay.
5) If the GP's check OK and they are getting voltage, it's time to check the injection pump timing. On the TDICLUB, we prefer VCDS (was vag-com).

Post back if you have any questions or issues. And, feel free to copy this into a new posting, if you choose to create a new thread.

Tony

 

[GeWilli]

is one of those the starter relay? or is that somewhere else...

 

[50harleyrider]

96 b4 glow plug fuse location

I'm rerally fuse confused on the location. I have two identical 96 B4's and the factory 50 amp glow plug fuse is located on the firewall next to the N-75 valve on both cars. Wingnut's photo shows it up under the dash. Are there two fuses? Care to comment Wingnut?

 

[compu_85]

That's the fuse for the coolant glow plugs.

-Jason

 

[dieseljunkie]

I'm rerally fuse confused on the location. I have two identical 96 B4's and the factory 50 amp glow plug fuse is located on the firewall next to the N-75 valve on both cars. Wingnut's photo shows it up under the dash. Are there two fuses? Care to comment Wingnut?

First, you must not confuse Wingnut with Lug Nut. Lug Nut is a bigger nut! Second, the glow plug fuse is in a horrible location, hidden behind the fuse relay panel. I by passed it and the glow plug relay and have my own glow plug relay and fuse right at the battery + terminal. No more cursing and fire hazzard.

 

[50harleyrider]

OK-It looks like I need to unfasten the fuse and relay box,lower it and the the fuse will magically appear? Thanks and sorry Lug_Nut

 

[TonyJetta]

OK-It looks like I need to unfasten the fuse and relay box,lower it and the the fuse will magically appear?

Kind of...you still need to lay on your back with a flashlight to see up there high enough.

Tony