FG Electrical Problem - Location of Earth connections in cab?

[gait]

2005 FG649 Aus.

Can anyone tell me where the major shared earth connections are for headlights, exhaust retarder, blower fan, aircon, electric windows, are?

First symptoms after stopping, a few minutes after ignition off, smoke and smell from under dashboard to left of instruments.

Disconnected battery quickly.

10A fuse for "internal light" melted but still intact. Seemed a bit high value for just light. Removed fuse.

Reconnected battery. Small spark. Bit of a whirring noise. After about a minute all dash lights came on. More smoke. Disconnect battery.

Turned off blower fan. Reconnect battery. Same again, with addition of starter motor started running. Ignition definitely off. Disconnect battery.

Dismantled most of dash. Wire to oil level test switch melted. No insulation left. Melted to a couple of other wires. Disconnected it. Made sure no odd connections.

Reconnected battery. No spark. No lights. No smoke. Started engine ok. Battery light slow to go out. Alternator volts a bit higher than normal (at 14.6v, normally about 13.8v). Engine warning light on - I'll check the code later.

We are mobile again - we were stopped on a mountainous Nepalese road.

Then realised that headlights, aircon, electric windows, blower fan, exhaust retarder, not working.

I'm guessing that a major shared earth connection has come loose. Power found its way through the oil level test circuit and was too much for the thin wire.

So. I'm about to head into the manual. Shortcut is, can anyone tell me where the shared earth connections are for alll those things I mentioned?

 

[SkiFreak]

Rule number one.... don't let the magic smoke out.
Hope you find the cause, sooner rather than later.

 

[gait]

thanks Owen. The special magic smoke is still in there .......... at least the engine runs.

I'm a bit surprised the circuits could be designed so that aircon, blower, and electrical windows can fail at the same time - its a bit warm here - ... just as well the doors open!

Cross reference between circuit diagram and physical location drawings is hard for me without a key to the diagrams. And of course I'm not too sure if I have a wrong circuit diagram or my hypothesis is wrog ... the wiper/washer still works but the circuit diagram suggests it shares a ground with the others on the list don't.

But slowly things are leading to what should be a collection of ground connections adjacent to the big box under cab, aligned with hinge, that has all the cab-chassis connections. Dark now so the excitement will have to wait until morning.

Scary bit. I removed the melted interior light 10A fuse. I have zero resistance across the fuse box terminals and the interior light works.

Any other suggestions as to root cause gratefully accepted.

 

[whatcharterboat]

Hi Julian,

Yeah. That is scary.

There is two main 6mm earths that run up in the harness from the battery through the plugs in the black box (next to the small cab earths). One does the computer, ignition etc and the other does some of the bigger loads such as AC, fans, etc. The earths down near the black box under the front cab are instruments, lights, etc. To me it sounds like one of the main 6mm earths that failed. It should go up into the back of the relay/fuse box. Stretching the memory a little. A mate has a 649 nearby that I could double check on. The other spot might be to check the earths at the back of the AC control switches but that my first hunch is more likely.

Hope this helps. Please keep us posted.

Kind regards
John

 

[gait]

thanks John,

found the multiple small earths next to the big cab/chassis junction box. They certainly don't look big enough for the sort of loads on the things that don't work. Very clean. No resistance before I cleaned it some more. No change in symptoms.

I have most of the dash covering off. Easy access to back of fuses and removal of aircon/blower switch panel.

I'll also check what I actually have power to. And trace the melted oil level wire behind the speedo. Attack from both ends as it were.

I had the cover off the big junction box and looked remarkably spotless inside. Didn't dig deep enough to spot the two earths - thanks.

Any checking you can do would be much appreciated.

I've taken to pulling the fuse for the starter circuit so it doesn't decide to start turning while engine running ....

I have a deadline to enter Myanmar on 20th Feb so have to keep moving a bit each day.

 

[whatcharterboat]

thanks John.......

Any checking you can do would be much appreciated

I've taken to pulling the fuse for the starter circuit so it doesn't decide to start turning while engine running ....

.

Yeah, no problem. I'll drop over to my mates place tomorrow arvo and have a quick look. Have you pulled the fuse panel off yet?

Re: the starter circuit. I had a mate put his old EH wagon in the auto leccy shop ....this was way back........anyway it was parked in the car park out front on 6lane Bowen Bridge Rd just down from the RBH and by itself the starter engaged and it drove diagonally across 4 lanes and had a head on with truck. True.

 

[gait]

found another earth connection to chassis near the big junction box. Clean but cleaned it anyway.

Got to the "doubting sanity" stage. Headlights now working (but maybe they always were, maybe I just didn't check enough, and disconnecting the earth I just cleaned doesn't effect them!).

Also central locking now working, but not electric windows.

Currently electric windows, exhaust retarder, blower fan and aircon not working. Interior light now working, despite fuse removed.

At back of fuse box interior light wire melted. Perhaps explains timing of initial smoke. Just after we stopped, ignition off, driver's door open.

I also checked power to fuses. All good.

Can't find any black wires in the loom at connectors. Time to check the colour of earth wires in diagram.

 

[gait]

I'm sure there was a post about the possibility of multiple problems. very prophetic. Not sure where its disappeared to.

First, the connector I went looking for isn't there. "J05" should have had several earth wires from blower/aircon, and only earths. The wiring diagram is now just a (useful) guide, not definitive.

The electric windows have power to the switch, a good earth, but no action. The electric door locks using same power and earth work.

The blower / air con have power to fuse, blue white wire out, disappears into loom, no power on the red wire to the switches. Earths ok.

I'll fault find the blower first as its simple and there are no relays involved (the presence of separate control and power circuits most other places confuses. Electric windows are also relay free though there's some electronics.

Exhaust retarder, the switch for engine warm up was disconnected when I removed the dash panel. Reconnected but no change.

I'm about to start stripping off sticky tape from parts of the loom. I'll start following that power wire for blower fan from the fuse box. If I get fed up of that I'll apply power directly to the blower switch, stand back, and see what happens. But slowly slowly, I'm not in the best position to allow for creation of more problems.

There's a large part of the loom tucked up behind all the dash, runs right across the vehicle. With torch and mirror I can see the trace of something melted.

"Bother" as they say.

 

[whatcharterboat]

Hi Julian

Yeah. I still think you'll need to check the 6mm earth that goes up to the relay panel.....just under the glovebox . Pull the glovebox out and the panel below to give access. I went to my mates place. He still works on a 649 regularly and knows them inside out. Loosing that earth was his gut feeling too. He thought it may have broken in the harness but I'd be checking behind the relays first.

If Chocko (engineer) sees this post....could you please offer some advice?

Thanks mate.

Kind regards
John.

 

[ianc]

Julian,
I'd noticed that you blog had paused but that you had moved to Nepal according to your tracker. Bummer on the electrical problems. I'm afraid I'm not much help on that as I don't have access to a similar vehicle.
The only thought I'd have is that, based on my experience, its more likely to bet he insulation on a part of the harness wearing through, shorting and causing knock-on problems.
Good luck on the hunting.

Ian

 

[kerry]

Did you say that the interior light is working with the fuse removed? I wasn't clear on that. If it is, it seems to me that the problem is not in a ground but in a hot wire shorted to the cab so the light is picking up 12volts from the cab itself. Maybe I misunderstood.

 

[SkiFreak]

...to me that the problem is not in a ground but in a hot wire shorted to the cab so the light is picking up 12volts from the cab itself

That's what I thought when I heard about the light working without a fuse.
As Kerry and Ian have said... seems to point to a problem in the loom.

 

[whatcharterboat]

Hi Julian, any progress on your wiring fault? Regards John.

 

[gait]

well .... after about 10 days of analysis, testing, checking .... I finally got to doing.

The interior light fuse was melted and hadn't broken the circuit. The wire had melted its insulation full length and caused all sorts of "cancer" in the rest of the loom. Simply - "fail to safe" failed by not "failing to safe".

All earths apparently intact.

Basically there are "power" circuits through relays to things like lights, aircon, windows, etc. And there are "control" circuits with switches to operate the relays. Looks like damage to the control circuit between ignition and somewhere it splits to individual circuits.

I haven't found that damage.

I now have a loop from fuse box to aircon/blower panel to by-pass the short/break. Another short loop at the electric window door switch - and cut the normal wire from ignition, otherwise engine stays running with ignition off!!!!

The engine running bit was intermittent. As also was wipers being switched on from interior light switch. There's still a problem lurking somewhere.

With those two loops the alternator light now behaves normally.

There should be a fuse for that ignition "control" circuit. In the FE circuit diagram its very clearly there. Not in my fuse box. I received an FG electrical manual by email today, from Brisbane dealer (first internet since problem) and will investigate.

Exhaust retarder fuse had blown.

Work arounds at best. We are quite nervous about "what next". Hard enough on its own when at home. Difficult to add solving problems like this to the mix of crossing borders and wondering where we'll sleep or find food. We had some deadlines from visas and convoy through Myanmar so wanted to keep moving.

 

[ianc]

Hmm. Not optimal, but are you back to seeing predictable and acceptable behaviour with the temporary bypasses on the control circuits?
The big plus in joining up with the convoy is having other people to talk the problems through. It doesn't matter if none of them have the skills to fix the problem. Just the act of you explaining the issues to others will almost certainly bring you to a good conclusion more quickly.

I hope you get on top of the problems soon. BTW - I'm very glad to see the blog has restarted