[Mexglx]

Ok, I used an electric powerwasher to wash my ´04 V8 TReg including the grill area. I did a little extra time spraying through the grill to hopefully clean the radiator and oil cooler.

• The day after I noticed the external temperature was displayed higher than actual temp by 10 degrees and climbed to 104 deg ambient when it was a 75 deg morning.
  • I disconnected the sensor behind the VW grill emblem, sprayed some parts cleaner on the terminals, blew with shop air and connected ohmmeter. I put it in a cup of ice and saw the resistance rise and then removed from ice and saw the ohms drop. I checked the wires at the sensor and they all looked fine. I followed the wires down a ways in the loom and still looked fine. Figured I would re-install. Unfortunately, it is still not working. It quickly shows rising temperatures far in excess of ambient. Before I replace it I want to see if it is related to the other issues.
• Also within a day, I had an airbag fault light. Faults 01738 (G283) Front drivers side crash sensor and 01739 (G284) Passenger side airbag crash sensor - static- closed. I don´t know where these are in order to check connections. Are they under the headlights? What´s the best way to get to them? I can find any pics or DIYs on them anywhere.
• Then a week later, I had a hood open light despite the hood being firmly latched. I had driven 20 minutes in the rain before it came on while I was driving. I checked the forums and saw multiple posts about the stereo not seated correctly. I removed the stereo as mentioned in some posts. My CD/Nav unit does not have the micro switch some said may be the issue. So I figured I´d check the hood latch assembly.
  • I removed the grill, disconnected the harness to the hood sensor. The hood light dimmed a little. Hmmm. I connected the terminals in the harness with a piece of wire to see if that would turn off the hood light. It dimmed the light but didn´t turn it off. 2 things about this. I expected it would either turn off the light or not. If jumping terminals turned off the light, I would assume the switch at the latch was bad. If it didn´t, then I would know I had a problem somewhere else. The fact it dimmed threw me. When I removed jumper wire the hood light would brighten.
  • I then removed the whole latch assembly to check it. With the harness connected, I could push the microswitch down with a small screwdriver and make the light dim, like when I jumped the harness terminals, but the lights would not go out.
  • I followed the wires down the loom all the way to where the hood and ambient air wires meet a larger group of wires at a ¨T¨. I didn´t see any cut or exposed wires up to and in the ¨T¨

My main question is do all of these three systems (crash sensor, air temp, hood latch sensor) share a circuit or share a ground or fuse or something in common that could cause them to be erratic after getting wet from a cheap lowes electric powerwasher.

Anyone have a similar trifecta situation? What would you all think would be the top three steps to start the troubleshooting with?
Thanks for your input.Overview of hood sensor issues, ABS Crash Sensor and Ambient air temp sensor.

 

[lachoradkov]

That’s an interesting thread. Hopefully you’ll find that ghost

 

[Mexglx]

That’s an interesting thread. Hopefully you’ll find that ghost

Thanks. I hope so too.

 

[meanyhead]

I would check relay box (vw calls it "e box") driver side windshield cowl ("plenum chamber"). I bought my treg used and the fusebox was held together with only one of the six or seven or whatever screws there are supposed to be. Possible water got into there and is getting jiggy with the electrics, there are some fuses and power/ground distribution panels in there. My cowl was already cracked and I don't like removing wiper arms so I "carefully" broke it enough to swivel out of my way but still stay attached lmao

 

[Mexglx]

I think I found the problem. The harness that all of those wires go into was completely filled with water, and all the contacts were starting to corrode and have a bunch of rust. I will add a video of the area where I found a harness connector underneath the driver side headlight.

 

[jeffnhiscars]

The moral of this particular story is...keep the pressure washer away from the engine bay

 

[Mexglx]

The moral of this particular story is...keep the pressure washer away from the engine bay

Seeing where this harness is, it’s difficult to believe water got in there. I think it came in under the driver headlight and onto harness below and wicked in somehow. When I disconnected it, about a teaspoon of water came out. I cleaned with electric contact cleaner, tooth brush scraped female side with small screwdriver then sealed it all with dielectric grease. Also tested the drivers side horn (400hz) that seemed not to work. It’s dead. Straight 12V and nada. Tested other side and scared the **** out of me so it’s good. I’ll order a horn while I got the bumper off.

 

[TommiT]

Horn fix - squirt W40 or similar up the trumpet.

Wait 24 hours.

Then go somewhere where you won't be a nuisance and lean on the horn button long and hard.

With a bit of luck there will be a squawk or two and then normal service.

If it works remember to use the horn once a week thereafter!

 

[Mexglx]

Horn fix - squirt W40 or similar up the trumpet.

Wait 24 hours.

Then go somewhere where you won't be a nuisance and lean on the horn button long and hard.

With a bit of luck there will be a squawk or two and then normal service.

If it works remember to use the horn once a week thereafter!

I’ll try that. Thanks.

 

[TommiT]

Also, as a matter of urgency, check your air filter to see if it is completely dry.

If not change it ASAP before it gets ingested.

 

[Mexglx]

Here is a wrap up video. Air Temp Sensor no longer erratic. Hood Open light on dash is now off with hood closed. No more air bag light on dash.

 

[AlexUK]

Good info here, thanks.

I assume I could access that electrical connector by simply removing the front left wheel arch liner, instead of having to remove the front bumper and headlight?

 

[Mexglx]

Good info here, thanks.

I assume I could access that electrical connector by simply removing the front left wheel arch liner, instead of having to remove the front bumper and headlight?

I’ll have to look at the pics. I don’t know for sure. I put the air suspension all the way up so getting to the fender screws with a 90 degree drill extension made removing the bumper cover a breeze. In this pic it does look possible. Also slightly easier. Since I was trying to troubleshoot I took the whole cover off. I think you are right though. Now that I know, taking that fender liner off, seems a little quicker.

 

[Mexglx]

Horn fix - squirt W40 or similar up the trumpet.

The horn is dead. I tried WD40 and actually feels like it fell apart internally. Loose pieces flopping around inside. No sound at all when connected to 12v. Thanks for the idea anyway. I tried.

 

[Mexglx]

I am still getting water in the harness connector under the headlight. Anyone have any ideas where water could be getting in from? We had some rain and it got in there. Twice, since I first posted I have removed water from the harness. The tell for me is the ambient air temp sensor starts reading higher than ambient by 20 Deg or more. I did verify you can get to the harness through the fender. The connector was wrapped in electrical tape this time. I cut it all off and opened it and another spoonfull of water came out. It looks dry where the wires go in to both male and female side. Could it be wicking through a wire? If so, anyone else ever have this happen?

 

[Mexglx]

I took a close up of the harness and I think an internal seal has fallen apart. See the purple gasket missing in certain parts. I placed a small rubber band in there and dielectric grease then wrapped it in plastic wrap and electrical tape to see if it seals. I’ll also see if I can order a new connector and swap the pins to a new connector next.

 

[SaVAGeSoot]

It's the weather seal on the inside of the connector as you've already noted.

 

[jeffnhiscars]

I was advised to pack grease around that type of connector to mitigate a damaged seal. It's worth trying IMO

 

[meanyhead]

It's definitely worth buying a new connector before it leads to other problems. It seems you have tracked down the problem so fix it before the VAG gods get angry. 👍

 

[Mexglx]

…so fix it before the VAG gods get angry. 👍

When you’re right, you’re right.