MattDevoCustoms

all of these HUs have at least 4 RCA outputs (FL, FR, RL, RR) though the front and rear plugs can sometimes be located on different harnesses. You can run RCAs from them along with the amp turn-on wire from the HU to your new aftermarket amp.

which unit specifically did you purchase?

dxb9er

@MattDevoCustoms https://www.aliexpress.us/item/10050...apt=4itemAdapt (7862 128G Fiber` for Bose)

niklaskhf

Hi everyone
I have run into a bit of an annoying problem and searching around has not helped much. I hope that someone here may know what my problem is, or how one may diagnose it further.
This is my first time working on a car, so I don’t have much idea what I’m doing.

A couple months ago I installed the Owtosin Android headunit in my 997.2. The car is an imported car (into Japan), and as such has a bit of an unusual setup that looks something like this - from the factory:
1. CANBUS goes into a CANBUS decoder and outputs things like ACC (12V on key)/ILL (12V on illumination/Brake/Reverse/…
2. CANBUS outputs go into a harness, together with ground and battery wires
3. Harness goes into adapter which goes into the headunit - this adapter is different from the usual ones but does the same thing, just without any CANBUS wires
4. The car has an external amplifier. The amplifier takes the following inputs from the headunit:
- 12V trigger to turn on - this is connected to ACC. This is connected with a butt connector.
- 4 RCA inputs for the speaker inputs

Now, to describe the problem:
When putting the key in, I can hear a light sound that indicates the speakers getting power - this was always there. Afterwards, it’s completely silent until the headunit powers on and starts playing music.
When turning the key a bit to turn on the AC etc, there still is nothing out of the ordinary.
When turning on the engine, suddenly a constant beep starts coming from the speakers. This beep is constant at all RPM and does not change in volume when adjusting the volume at the headunit.

When initially setting up the headunit, there was no beep. Recently I attempted to install a backup camera, which involved me splicing into the CANBUS wires to install a different CANBUS decoder (that was supposed to work natively with the headunit and came in the box). I wanted to do this to eventually also get access to the steering wheel controls, if I were to upgrade to a newer steering wheel.
After this, the beep suddenly started, which led me to undoing the splice and going back to the original setup. I totally expected this to eliminate the beep, but it unfortunately did not.
Afterwards, the CANBUS wires that go into the decoder now have a butt connector in them - I know this is not ideal, but this is only for the headunit so I was thinking that this may be good enough for now, as long as ACC/ILL/… still work as before.

Things I have tried so far:
- I read that there may be a ground loop issue. I have tried to put a ground loop isolator between the RCAs. Interestingly, this initially helped a bit when using the new CANBUS decoder. It turned the beep into more of a white noise. However, when going back to the original setup, the ground loop isolators no longer change anything and the beep remains constant.
- I have tried connecting the 12V trigger to a different ACC wire - no luck here (makes sense, since this only turn on the amplifier and shouldn’t really have any impact on the sound)
- When unplugging the RCAs, the sound goes away, so it’s definitely something in the upstream of the RCAs (headunit or before)


The questions that I have now:
- What else can I try to troubleshoot? I have a multimeter, is there any point measuring something around the RCAs to closer pinpoint the issue?
- If it’s not a grounding issue (ground loop isolator has no impact), what else could this be?
- Why does this only happen when the engine is on? I read about issues with charging the battery from the alternator, but it doesn’t seem to be the cause since the volume is steady at different speeds.
- Can this in some way be related to the CANBUS? There is likely some extra resistance there from the connector, but my understanding is that this should not impact the ground or power delivery, since the CANBUS decoder just provides some 12V triggers, and the actual power comes from the battery.

I’m getting quite frustrated and having a lot of regrets about touching a running system.
I’d be grateful if anyone has inputs about how this may be resolved, or what the problem could be. Unfortunately just playing the music louder doesn’t mask the beep

MattDevoCustoms

ok, so this HU uses the older RCA output config. The front outputs are on the harness you pictured, labeled audio out L/R. The rear outputs are on the same plug as the canbus inputs (white 2 wires) and there's a passthru cable sellers used to include for that:



I think I have a few extra still, so DM me if you'd like one and can drop it in the mail for you.

iamuwere

997.2 Turbo Cab.

Ordered the android 12 Qualcomm 6g/128g model. CANBUS and Dual FAKRA



What am I missing?

Also, I have four antenna connectors on my factory radio. 1 Blue, 1 Black, and 2 yellow. Which is supposed to attach to this dual fakra and how? It seems the black makes a semi decent connection to the radio but I can’t connect two of these to the adaptor

order

back of the factory unit with four antenna type connectors. I can't find documentation on which of these to connect


@myw @MattDevoCustoms

Graufuchs

The 997.2 connectors are much different than the 997.1 connectors. Do they make a 997.2 harness?

iamuwere

997.2 is what I indicated when purchasing and it has the dark grey of 997.2, not the silver of 997.1

MattDevoCustoms

black and yellow on the left of the above picture are the 2 radio antenna plugs; if the 997.2 uses an external antenna amp like the .1, it will need to be / should be bypassed. Blue is GPS - you'll need a SMA to FAKRA adapter to connect to the factory GPS plug ($7 on amazon). Yellow on the right appears to be a LVDS (display) connector and will not be used for a USB port and can be connected via a 3rd party adapter

ZedZed

The yellow one on the rigght looks very much like the OEM USB connector to me.

MattDevoCustoms

that makes sense - in which case you can use an adapter plug to connect it to one of the USB ports on the new HU. something like this:

Jabra1871

Just bought the 7862 with Bose for my 987.1. I installed the unit and it powers on but no sound, but I am yet to splice in the cables. Do these cables even impact the sound; my understanding was they are just for power? Are there any good instructions on how to splice the cables? Can you use a Wamo connector?

MattDevoCustoms

Assuming you purchased the Heregoes 7262 unit, and assuming the 987 HU is wired identically to the 997.1, then you likely need to splice in the constant power (yellow), accessory power (red), and ground (black) for the MOST adapter box into the main harness, and connect the front line-level output RCAs from the HU to it. You may also need to wire in the amp turn-on wire as previously discussed in this thread.

ZedZed

Adding to MattDevo's comprehensive reply, also you will need, of course, to connect the fiber optic cable (usually orange) to the MOST box. The MOST box may well have some sort of 'socket protector' piece inside the hole where you plug the fibre optic connector. If so, carefully remove this before attempting installation of the fiber optic connector. I've circled it in red on the image below. It can be quite tricky to remove, so take your time with it.



EDIT:

I missed your query about connectors. I find that T-Taps are useful for the small wires on the MOST box and harness. Something like the ones in the image below. You can get them from Amazon. There are lots of different types of connectors for splicing into existing wiring, but I find these are easy to use, make a good connection and work well. The image shows a twin wire version but you can also get them in single wire versions.


.

I wouldn't use Wago connectors, or any other sort designed for domestic wiring. The wires on the car harness are too thin to get a good connection with Wago-style connectors. Best to use one of the numerous connectors specially designed for automotive use. Also, I wouldn't just twist the wires together and use electrical tape either, since this is not the best way to ensure a reliable connection.

Jabra1871

I've spliced these today but still getting now sound. Haven't heard of need to wire in the amp before - do you have instructions? I've just tried searching but couldn't find anything.

Jabra1871

Thanks for the response. I've now got the most wired in (did have to remove protector which I've done) and got some connectors like the ones above. Frustratingly still no sound..