Technical Wierd buzzing and eraatic voltage

[azzer1704]

Hi there
I'm new to the forum so please go easy on me lol.

I've recently purchased a 2004 fiat ducato 2.8 jtd autotrail motorhome.

I'm mid way through fitting an android head unit, and I've run into some strange electrical issues.

The main issue is a pulsating buzzing noise coming from the dash, along with voltage readings all over the place on the display in the motorhome (starter battery)

I noticed the buzzing seemed to be coming from this black box behind the switchboard.

I remade the connections as it was spliced I to a red/green wire on the white 20 pin plug. This seems to have helped, but still getting crazy voltage fluctuations.

Any body know what the black box is, or what the green/red cable is that it is spliced into.

Now when I plug in the switchboard I get a constant load buzzing sound.

Thanks

 

[bugsymike]

Hi there
I'm new to the forum so please go easy on me lol.

I've recently purchased a 2004 fiat ducato 2.8 jtd autotrail motorhome.

I'm mid way through fitting an android head unit, and I've run into some strange electrical issues.

The main issue is a pulsating buzzing noise coming from the dash, along with voltage readings all over the place on the display in the motorhome (starter battery)

I noticed the buzzing seemed to be coming from this black box behind the switchboard.

I remade the connections as it was spliced I to a red/green wire on the white 20 pin plug. This seems to have helped, but still getting crazy voltage fluctuations.

Any body know what the black box is, or what the green/red cable is that it is spliced into.

Now when I plug in the switchboard I get a constant load buzzing sound.

Thanks

Personally I would revert back to pre installation wiring and have it checked by an Auto Electrician, it may be an relay or something is getting a back feed or worse.
Electrical wiring fires can result in choking fumes as well as fires , not something you want to wake up to in the middle of the night!!!

 

[porta]

I’d agree with bugsy, get rid of the black box altogether and go from there…looks like something to do with the past radio installation.

 

[azzer1704]

I think perhaps the black box is something to do with the alarm, could be where it splices into the indicator wires for when you lock via the remote?

Anyway, the problem has worsened
The van won't start at all now, or lock. The voltage reader in the motorhome says 2v, (starter battery) however it turns over fine.

 

[bugsymike]

I think perhaps the black box is something to do with the alarm, could be where it splices into the indicator wires for when you lock via the remote?

Anyway, the problem has worsened
The van won't start at all now, or lock. The voltage reader in the motorhome says 2v, (starter battery) however it turns over fine.

Unless you are an experienced Auto Electrician, given what you are describing I would disconnected any batteries on the Motorhome and have it checked professionally.
If it catches fire from what you have mentioned, I suspect it would invalidate your insurance in the result of a claim.

 

[Communicator]

Recommended standard practice when working on vehicle wiring, is to disconnect the starter battery negative, and with an MH this is best extended to include the habitation battery.

It may have helped, if the pin number of the 20 way connector had been quoted. I have also had to deduce that the 20 way connector was that for the "Switch Control Module", but then 20 way connectors below the radio are limited in number.

The black box probably relates to an after market alarm system, or perhaps a tracker system.

If I have observed the photo correctly, there are only three connections to this mystery box. It seems to be connected in series with the red/green wire, and tap into a negative (black) wire?

Following from the above if the red/green wire is connected to pin 17, it is the 12V permanent supply for the hazard warning system via F53, but why interrupt that supply? Again is the buzzing heard with the connector plugged in, or when disconnected? Could it be a simple current limiter for the hazards, but then why 3 connections?

The "Switch Control Module" to which I believe the 20 way connector mates is another "black box" on the x244 Ducato. I have prepared my own table of connections, and connector pin B17 is the supply mentioned above. The associated eLearn circuit diagram for the hazard warning lights is E2020, but the module appears on many other diagrams. There does seem to be a connection with the OEM alarm system, but I found conflicting information when preparing my connection table for the Switch Control Module.

If the purpose of the original black box can be determined, it should be relatively simple to remove if that is the desired course of action but the 1mm red/green wire may need extending.

May I mention that I am not impressed by the quality of the crimping. Specifically there does not appear tto be any crimping on the insulation, and the blue crimps are probably oversize for the conductors.

I am concerned that the engine is not starting. It would seem that either the ECU is not being powered correctly, or an unknown immobiliser device has operated.

I will attach some further reading. Corrections and contributions are welcome.

 

[azzer1704]

Thanks for you advice.

Interestingly, when I was driving yesterday, the temp guage was all over the place, and today the speedo was going crazy.

I think the black box spliced into the 20 pin plug was a bit of a red herring.

The lock symbol is illuminated on the dash, so I'm thinking maybe an ecu problem or immobiliser issue. It's got an autowatch alarm system.

I wo der where the ecu is and how to treat the power supply to it.

 

[PuntoHowTo]

Thanks for you advice.

Interestingly, when I was driving yesterday, the temp guage was all over the place, and today the speedo was going crazy.

I think the black box spliced into the 20 pin plug was a bit of a red herring.

The lock symbol is illuminated on the dash, so I'm thinking maybe an ecu problem or immobiliser issue. It's got an autowatch alarm system.

I wo der where the ecu is and how to treat the power supply to it.

Leading on from @Communicator ’s post above that plug going into the hazard warning light switch connectors, depending on the model there probably isn’t a lot else on that switch panel, the “pulsing” you’re describing could very well be something like an alarm connection that is trying to flash the hazard lights but instead shorting a dash hi, to ground or trying to send a current to ground. I’d suspect that box may very well be the problem.

I agree there has been a proper hatchet job on a lot of the wiring in the dash, though this can often be the case with motor homes and is not actually that unusual, also it can often be very difficult to get any information on these wiring jobs as one motor home can be made differently from the next even made at the same time

 

[bugsymike]

Thanks for you advice.

Interestingly, when I was driving yesterday, the temp guage was all over the place, and today the speedo was going crazy.

I think the black box spliced into the 20 pin plug was a bit of a red herring.

The lock symbol is illuminated on the dash, so I'm thinking maybe an ecu problem or immobiliser issue. It's got an autowatch alarm system.

I wo der where the ecu is and how to treat the power supply to it.

Just a thought re lock symbol, if you have a spare key try that.

 

[Communicator]

The ECU is on the inner left wing, outboard of the air filter, but I would not worry about that yet.

The key code symbol is serious. The engine will not start when the padlock is shown. It could be that there is a loose connection somewhere, and the code receiver is not receiving sufficient power, but there are many possibilities. +The key code receiver shares a supply with at least one power input to the ECU, via F18 in the engine bay fusebox. Very simply, if the code receiver located under the steering column, fails to recognise the key it will not respond to a coded request from the ECU, and if the ECU does not receive a coded reply, it will not allow the engine to start.

The attached fusebox chart is specific to my vehicle, which does not have Aircon or ABS, but still useful?

 

[azzer1704]

Thanks to those that offered useful info.

I removed the black box behind the heater controls which turned out to be a signal beeper for the hazard, indicator lights.

The weird voltage readings were due to an existing poorly made splice connector near the starter battery, which must have been a sensor wire. I remade that and all is well.