Instrument Cluster issues after rebuild

[kmjunge]

I recently completed a rebuild/refresh on my 98 Jetta. I have the engine back in the car, it runs and drives pretty well and I'm at the point of trying to work out all the smaller kinks. So here's what I'm running into in order of priority:

1. The instrument cluster warning lights all work but the speedo, tach, fuel level, and temp gauge do not work. I have done a voltage drop test on the engine block ground for the cluster and it seems to be fine. Is there something obvious I could have missed? The instrument cluster worked fine before I pulled the engine.

2. I'm thinking all my other issues are closely related to timing, specifically, the only fault code I'm getting is the N108 faulty/intermittent. My timing is all the way advanced (the vag-com reading is sitting at 255). The car drives but it has no guts (power). Before the rebuild I had the "00575 Intake manifod pressure control difference" issue but that appears to be resolved now (I installed new vacuum lines and intake hose). This leads me to believe my power loss issue is related to the timing and N108 fault code. Alternatively I guess it could be an N75 issue but I figure I should get the timing issues resolved first before chasing boost issues. Am I on the right track with that?

 

[Abacus]

Check fuse 21 and that the grounds are connected. If memory serves, a blown fuse 21 caused similar issues on a B4.

 

[Steve Addy]

At the cluster T28/3 (U1/10) is the main cluster ground (brn) and T28/5 (U2/13) is the ground for gauges / MFA (brn/white). The former is a shared ground with many things, I think it is attached at left side ground cluster behind the dashboard. I don't think this one is your problem, but I could be wrong.

The T28/5 (U2/13) ground starts with cluster connector T28/5 then connects at fuse fox box at U2/13, reemerges at G1/5 (engine harness) and then appears last at T24/4 (engine round connector) and then attaches at the bracket that holds that T24 large round engine connector. This wire is brown/white and the same stud mounting also has a brown/blue and a brown/green wire connection, the former going to the AC cutoff relay in the upper radiator hose, and latter going to the VSS in the trans.

A failure of grounding at this stud / bracket has a lot of consequences for different components.

Hope this helps.

Steve

 

[kmjunge]

I checked fuse 21 and it's good. There's a 30A fuse in there, is that right? The instrument cluster was replaced by the PO so I know it had issues in the past at some point.

After going through and carefully resetting and checking the mechanical timing I'm still getting the N108 code and a new glow plug monitoring code.

The N108 wiring has been tampered with by the PO at some point too.

It occurs to be that all of these issues have wires that go to the T24 plug and bracket. I've checked that ground and it seems good. Perhaps it's time to get more comfortable with voltage drop testing and tracing wires.

Otherwise the car is running pretty well.

 

[kmjunge]

I made some progress with the timing! Turns out the zip ties holding the T24 main engine plug together weren't torqued to spec... I added an additional zip tie and got it as tight as I could. This cleared the N108 code and glow plug code. I was able to get the timing dialed in and now I finally have proper power.

Unfortunately the zip tie did not fix the cluster issue so I still need to chase down the wiring that Steve Addy described. In the meantime I'll celebrate this little victory.

 

[Steve Addy]

I made some progress with the timing! Turns out the zip ties holding the T24 main engine plug together weren't torqued to spec... I added an additional zip tie and got it as tight as I could. This cleared the N108 code and glow plug code. I was able to get the timing dialed in and now I finally have proper power.

Unfortunately the zip tie did not fix the cluster issue so I still need to chase down the wiring that Steve Addy described. In the meantime I'll celebrate this little victory.

I'd undo the connector and make sure all contacts were good and probably apply some electrical grease to keep connections clean.

Steve

 

[kmjunge]

That's a good call Steve, I'll try to dive into that this week. I really need to get that cluster working now. The clock resets every time I put the key in and the the odometer isn't tracking. It's acting very similar to the cluster in the video below except without the pulsing fuel gauge and temp gauge. That one was a ground issue.

 

[Steve Addy]

That's a good call Steve, I'll try to dive into that this week. I really need to get that cluster working now. The clock resets every time I put the key in and the the odometer isn't tracking. It's acting very similar to the cluster in the video below except without the pulsing fuel gauge and temp gauge. That one was a ground issue.

The full cluster reset is something I've run into before but I can't recall what the cause was but I suspect it's something in the T24 round connector.

Does your T24 turn and tighten up properly?

I was reading in this ancient thread about issues with the T24 and what the OP figured out in the end. It's a potential starting point anyway.

Steve

 

[kmjunge]

The turning piece of the round plug connector is completely gone so the zip ties are the only thing holding it in place. I agree that the T24 is the prime suspect. I plan to test that theory by temporarily bypassing the connector to see if that gets me anywhere.

 

[Steve Addy]

Oh, now I'm understanding the problem, this explains why you're having issues. Would have been good to know that from the beginning...lol.

You're going to need to replace that in order to get a solid connection.

Those connectors are difficult to deal with, but I've managed to get everyone of them undone by twisting them back and forth gently with a channel lock pliers.

The other problem is I don't think that connector was used any other model, but I could be wrong. I know that the VR6 and ABA cars used a different one.

Steve

 

[kmjunge]

Yeah, unfortunately it didn't occur to me until this weekend...

Hopefully I can confirm the connector is the issue and then find one that isn't broken from a salvage yard somewhere...

Are there any other alternative solutions? I know the plug is NLA and the ones in the salvage yard are likely to be brittle and old.

 

[Steve Addy]

Yeah, unfortunately it didn't occur to me until this weekend...

Hopefully I can confirm the connector is the issue and then find one that isn't broken from a salvage yard somewhere...

Are there any other alternative solutions? I know the plug is NLA and the ones in the salvage yard are likely to be brittle and old.

No other alternative other than to build a junction box of some sort, which would be kinda messy.

Actually the ones I've seen aren't all that brittle since they've been protected from direct sun under hoods. You need the harness side so that might not be that difficult to locate used.

Eurovan VR6 1996-2004
Golf 1993-1999
Jetta 1993-1999

I'm not sure whether VR6 Golf (GTI) or Jetta GLX used this connector, it doesn't say, and the fitment information from VW is notoriously bad. I would guess that it's exclusively TDI powered Golf and Jetta even though it doesn't come right out and say it. The Eurovan might be your best bet for a used one.

Steve

 

[kmjunge]

Thanks for the info, I saw a couple of references to the gas Jettas having the same connector. I remember seeing a gas Mk3 Jetta at my pull yard a couple weeks ago, hopefully it has the piece in good shape.

 

[PassatLife]

If youre replacing the orb of death, definitely invest in a set of $10 depinning tools from Amazon or something. Makes the job a lot easier when you don't have to mess with picks and paper clips lol

I believe the connector is the same on all MK3s, just different pinouts. I have an OBD2 VR I could check later

 

[Mozambiquer]

One other thing to check, the solder joints where the plug attaches to the cluster can crack and cause issues like what you describe.. I had that happen on my Mk3, and the speedometer/odometer/tachometer didn't work.
I used a soldering iron and heated it up and melted it back together. I didn't have any other issues after that.

 

[kmjunge]

I jumped the connector by basically splicing a new wire from the brown/white ground wire before the connection to the negative battery terminal. This brought back the fuel gauge and tach but the speedo still didn't work and the oil pressure warning was beeping. I realized that the VSS and oil pressure sensor are both attached to the T24-Orb-of-Death death connector. So that pretty much confirmed the issues are mainly at the T24 connection.

I swung by the pick and pull and the lady told me they did not have any late 90's VW's on the lot (even though I had seen one just a couple weeks ago). She said they had been crushing cars lately. I took a chance and paid the $2 to get into the yard to see for myself. Sure enough the green 2.0 gasser I had seen was still there. I popped the hood and the connector was sitting there still intact. About 30 seconds with some wire cutters and it was out. They charged me $3.18 so I'm into the new plug for $5.18 total.

Luckily I do already have the depinning tools so that's probably what I'll be doing tonight... hopefully this fixes it.

 

[ToddA1]

Someone here recently had a similar issue. Their ground wire that goes to the stud was filled with corrosion. Personally, I think that bracket is a poor design. The bracket relies on the block’s ground. If the bracket is corroded, it can’t provide a good ground, to whatever’s connected to it.

Getting that bracket off to clean, is fun…

-Todd

 

[kmjunge]

For everyone's information the T24 connector from a 2.0 gasser is not the same as the T24 connector in a 1.9 TDI.

 

[ToddA1]

A lot smaller, iirc. Is there actually something wrong with the connecto, or the terminals, within?

-Todd

 

[kmjunge]

Yeah, the part of the connector that twists to lock down the connection is completely missing from mine and most of the tabs that hold the twisting bit on are broken. The previous owner must have really struggled with it. It was zip tied together and running in limp mode when I got it.

 

[PassatLife]

Yeah, the part of the connector that twists to lock down the connection is completely missing from mine and most of the tabs that hold the twisting bit on are broken. The previous owner must have really struggled with it. It was zip tied together and running in limp mode when I got it.

Yeah if you're not familiar with how it unlocks you can really butcher it...

This is the one off a mk3 VR, it looks like it has a lot more pins than my AHU but I could be wrong

 

[Steve Addy]

Yeah if you're not familiar with how it unlocks you can really butcher it...

This is the one off a mk3 VR, it looks like it has a lot more pins than my AHU but I could be wrong

It is different, I remember dealing with one before.

For everyone's information the T24 connector from a 2.0 gasser is not the same as the T24 connector in a 1.9 TDI.

I suspected as much when I posted up the information earlier today. I remember detaching the ABA connector and finding it very small comparatively. I also remember disconnecting a VR6 powered Passat and finding the pins to be very different.

This is the way the info provided by the VW dealer works, it will give you some application info but often there's more detail that it lacks.

The only other candidate is the VR6 powered Eurovan, which VW says uses the same connector.

Steve

 

[PassatLife]

ETKA is giving me 3A0973131 for the engine side, and 3A0973103 for the chassis side. ECS shows both available, at $170 total. You could probably buy a complete harness for that price lol.

Try messaging tdc_shop on Instagram, he does a lot of VW swap harnesses and might have a spare plug kicking around

 

[ToddA1]

ECS doesn’t really stock these parts… they source them from a dealer network, so the prices don’t surprise me. I think I sold the complete engine harness and fuse panel, from the Rotbox, for about $100-150.

-Todd

 

[kmjunge]

Yeah, that's kind of what I'm looking into. A local yard about 45 minutes from me may have a plug but they will only sell the whole harness for around $200-$300. I skimmed over TDC's site and it looks like they use the connections and plugs from the donor harness you send him but it may be worth seeing if he has a spare.

 

[ToddA1]

I did a quick google search and that “housing“, is coming up NLA. What’s NLA in the US, isn’t necessarily NLA, overseas. Did a quick search of euro sites, and in this case, it is NLA.

If you reach out to ECS, they’ll probably tell you nobody has ever ordered that part, and the catalog was never updated. Happened to me last year, for an evaporator (or AC heater core), for my Rabbit GTI.

You do realize there are other places to by parts, other than TDI Club, correct? Maybe Abacus will be able to pull through, for you…

-Todd

 

[kmjunge]

Yeah, I saw the ECS listing but had the same thought that you did. I've been looking overseas too with no luck. I looked for wiring harnesses on car-part too but most are 2.0's or they don't specify the engine. This is going to take some digging.

An older post in the conversion forums mentioned an aftermarket 24 pin connector but I haven't been able to find that connector yet either.

https://forums.tdiclub.com/index.ph...engine-electrical-connector-round-ahu.390630/

 

[PassatLife]

There's a local u-pick yard near me that has an AHU A3 I could probably cut the connector off, if it's still there. Only thing is they're in an area that was completely flooded a few weeks ago, not sure if they're accessible or not atm...

 

[Abacus]

I’m hitting the yard again on Saturday. I need more parts to send out for previous people.

 

[kmjunge]

Thank you!!