V35 Sedan - Electronics Problems After Parking In The Sun

[10 4]

01 V35 Sedan - mums car.

After parking in the (hot) sun for a while, the dash instruments don't work, nor do the dash lights.

Temp display works - but air con power / sound system power - nothing works.

Then everything starts to work after a while when it cools down.

As you can imagine, this gets annoying...

Any ideas?

Edited November 17, 2013 by 10 4

[The Max]

Given it affects AC and stereo control as well, I'd say you have a dry joint somewhere in the AV system, starting with the AC+instrumentation amp module. That said, I'm not familiar with the V35 as much as I am with the V36 but that's where I would start.

Get your hands on the factory service manual for it and trace the schematic back from the dash cluster (or combination meter, as it's called in the manual). See which module it plugs into and then take out that module for an inspection. Dry joints aren't all that obvious to pick up on without some serious magnification but if you're good with a decent soldering iron (i.e. a proper temperature controlled unit), if you pick the logical points where it wires into and resolder the joints with just a little touch of fresh solder, that would be your starting point. Should it still exhibit the same issues, keep working your way through the circuit, reflowing all joints leading back until it comes alive.

Also, check for any capacitors which may have dried out. It's pretty obvious, even with the SMD types, where you notice the can having bulged out at the top and/or sides. Pay particular attention to any electrolytics which may have been also heatshrinked as well. Carefully cut the heatshrink off and inspect accordingly. Be sure to replace them with not only the same value capacitance but also the same minimum working voltage ("WV"). You can go to a higher WV rating if it physically fits but don't go lower. Also check for any leaked electrolyte on the board, which can result in corrosion of the copper traces. Be sure you clean it with some circuit board cleaner and double check it's all gone by applying a little heat from your soldering iron and wafting it for any unusually pungent smells. If you still smell something pungent, it's not entirely cleaned up.

Given the problem is thermally related, I'd say the cause is a fairly simple one, hence why I've mentioned dry joints first. The caps may not really be the result of a thermal issue but they may be possibly storing enough of a charge eventually to power up so while you think it's because it has cooled down, the reality may be that it just had enough time to eventually charge up.

The less likely cause is a bad semiconductor, typically a transistor or two supplying power to all those devices. In which case, diagnosing a bad one while in circuit isn't as easy, particularly when dealing with a thermal issue. That takes a can of good freeze spray (such as Electrolube's MCF400) and hitting the suspected components until one of them gives you the expected result.

Unless it's a common fault mentioned on one of the G35 forums in the US or something, you'll be hunting for the culprit but you'll feel very satisfied for having fixed it. Best of luck and let us know what you find. You might save someone else's bacon one day.

[10 4]

Hey man, appreciate the detail. Unfortunately I'm useless. Will show mechanic next time its serviced.
Otherwise will keep googling US forums - ta.

[10 4]

Old problem still not fixed - no one has had same issue as far as I can tell....

New issue today: THUD/CLUNK into drive / reverse and when put into tiptronic mode, its stuck in 4th gear. Restart car = same issue. AT check light comes on then goes off so no issue there. Also speedo works, fuel gauge works, tacho and temp gauge does not work.

Is not driveable atm.

FFS.

Edited April 28, 2014 by 10 4

[scotty nm35]

Just because the AT light goes off, doesn't mean there is no fault.

The auto is in limp mode, you need to get a Consult unit on it to find out the code. Wish I could help but it would be a long drive.

[10 4]

Ok, will do it next service time. Cheers.

All is well now after I left it alone for a day... -_-

[scotty nm35]

Every time you re-start the car it returns to normal operation, as long as the reason for the fault is gone.

Sounds like an overheated transmission fluid fault. You may want to get it looked at sooner rather than later, it's not like we are in summer anymore, so if it's overheating you may have other issues.

[10 4]

I like the theory.. But the trans thud / stuck in 4th along with 1 side of dash working.. only happened once when it was ~ 8deg outside in the morning. I started the car and that was it. Parked it, restarted same issue. Left it a day then all was well...

[scotty nm35]

It's not a theory, my trans has been in limp mode many times. It gets locked in 4th when it overheats/faults.

I would say you had an issue with the temp sensors in the gearbox, but only a Consult unit can read it properly to prove the fault.