So I'm driving along yesterday, thinking what a great car my old Mondeo has been since I got it.....

[indy4x]

Non of the LandRover's I owned had a sunroof, but they leaked nonetheless.

I specifically wanted a Disco 3 SE as they didn't have sunroofs, still leaked, easy fix tho

 

[MetalMonkey]

Why not? Other than restraints control modules, there's no reason to disconnect the battery every time you open or close a connection, after all, disconnecting the battery is just the same as pulling a plug or fuse ...

Generally good practice unless you are very sure about what you are doing or the modules are easily replaceable.

ECU's typically have multiple large multipin connectors to various other ecus in various states, which when pulled, are not going to disconnect or reconnect all those pins simultaneously or cleanly.

Designers also seem to love mounting them in inaccessible areas where they are difficult to get to the connectors.
Pins should be well protected, but depending on the type of connector occasionally it is possible to inadvertently touch something against something else whilst struggling with them.

Now the units should be designed to be reasonably tolerant, but it is not always the case - I've had a situation where I had to run additional earth to an ECU because the ground tracks have been blown off the board.
Unless there is a particular reason to keep the power connected while diagnosing a fault it is usually a good idea to disconnect the battery.

 

[Ubique]

There's a world of difference to connecting / disconnecting something with Term. 30 & 31 still 'live', and term. 15 in all it's variants also energised. It's definitely common practice in dealerships, battery disconnections can sometimes cause more problems than they cure, especially those difficult to get to ground connections where you end up with a little arc light show whilst you're putting it back on the battery....
These days, communication between modules tends to be CAN, LIN, MOST or FlexRay - none of which mind in the slightest being disconnected from their nearest & dearest, there are very few (if any now) module communication networks where actual power is supplied.

 

[Red'n'Black]

'Powered through their signal pins' - are you talking automotive systems? Most automotive sensors work on a 5V supply, the circuits being of the monitored design, so you will get between 0.5 & 4.5VDC at the 'signal pin' when connected, 5VDC open circuit and 0V short to ground, they are also specified to withstand 12VDC on any terminal. Over the years, I have never experienced any failures caused by disconnecting / reconnecting vehicle electronic devices, controllers or actuators with the battery connected. Clearly, restraints control modules require special handling - as does a certain part of an RX8 apparently.

OK, that's the bit I wasn't sure of. Good to hear that it's now standard practice.

 

[Morrisman]

So, the new washer pump arrived today, so I bit the bullet and jacked the car up, cut the wires above the pump, crimped them back together to prevent a repeat of the water problem, should the new pump ever fail. Double safeguard.

All was fitted in, fluid poured in, time to test.....

.....and nothing. Nothing pumped, nothing squirted...

So, off with the pump, had a good look, checked continuity across the pins, all good. I hooked up the original pump, it whirred when I pressed the button. So the electronic controls seem to work. Put the new one on, notified the power plug didn't click into place like the old one, so a good shove, in it went.

Now I have washers power spraying front and back, stronger than before as well. No flashing lights or other weirdness, so fingers crossed I caught it in time and there's no permanent damage.

 

[Morrisman]

I celebrated too soon, reversing out of the drive tonight I noticed I now have no reverse lights....
Everything else seems to work, but is it coincidental they were the first indication something was wrong?

Hard to believe that Ford needed a microprocessor to operate simple lights, and not just a switch and 12 volts. MOT is due soon, will it fail because of a lack of reversing lights?

 

[qwakers]

depends on the year.

4.6.1. Condition and operation​

You must inspect all reversing lamps fitted to vehicles first used from 1 September 2009 other than quadricycles and three-wheeled vehicles.

Reversing lamps must show a white light to the rear. On some vehicles it may be necessary to have the engine running before the reversing lamps will work.

At least one reversing lamp must be fitted.

Buses over 6m long may have 4 reversing lamps which may be:

• all showing white light to the rear
• 2 showing white light to the rear and one on each side

Defect	Category
(a) A reversing lamp inoperative	Major
(b) A reversing lamp lens defective	Major
(c) A reversing lamp: (i) not securely attached (ii) likely to become detached	Minor Major

 

[Morrisman]

It's 2012. Looks like I'm screwed. It's got to be something fried in the board, but I have no idea what or where to look at. It looked good when I had it out, no corrosion, green or burnt looking areas.

 

[qwakers]

i believe it is still technically legal to have the reverse lights operated off a clearly marked switch...

 

[Morrisman]

i believe it is still technically legal to have the reverse lights operated off a clearly marked switch...

I shall pull the connectors off the board, clean them all, see if anything changes.....then I might have to run manual wires from the gearbox switch to the lights somehow.

 

[dobbslc]

Is it worth checking the bulbs and reverse switch before delving into the ECU again?
Edit:
I once spent hours messing around with the headlight switch and relays on my wifes Peugeot 206 cursing French electrics as the lights didn't work then found that both bulbs had blown

 

[Morrisman]

Is it worth checking the bulbs and reverse switch before delving into the ECU again?
Edit:
I once spent hours messing around with the headlight switch and relays on my wifes Peugeot 206 cursing French electrics as the lights didn't work then found that both bulbs had blown

It'll be worth a look, but it would be highly coincidental that either of them failed, unless the original issue actually caused it.

 

[Seadog]

One of my number plate lights failed. I replaced it and tested. Still nothing. Started stripping the bulb holder out (MB estate, so it's above your head ).
I won't bore you with the rest of the story. Suffice it say that there was nothing wrong with the holder, or wiring.

I'd left the key in the ignition, which didn't allow the ECU to reset

That was a frustrating, and wasted hour from my life...

 

[ajlelectronics]

That was a frustrating, and wasted hour from my life...

We have all done daft stuff. When I worked for Heathkit, I realised that I had completed a repair on a communications receiver whilst still connected to the mains and powered up! That was just a very minor one. Also the stripping and rebuilding of an appliance to find that the mains outlet was actually dead.

 

[dobbslc]

Talk about taking your own advice then ignoring it!
Just this morning I stripped the stop start switch off my compressor as it wasn't starting up, couldn't find anything wrong with it.
Bit of head scratching and I noticed the blxxdy compressor was full of air that hadn't leaked away like it used to as I'd fixed the leak.
A quick blast to drain the air out and it started perfectly

 

[Red'n'Black]

We have all done daft stuff. When I worked for Heathkit, I realised that I had completed a repair on a communications receiver whilst still connected to the mains and powered up! That was just a very minor one. Also the stripping and rebuilding of an appliance to find that the mains outlet was actually dead.

I think my worst one was back in the mid 90s, first job in electronics repairing PC monitors.
I forget what this one originally came in for, but once I had it working there was a small wobble on the picture. I tried all the usual suspects but couldn't get rid of it, ended up replacing bigger and bigger parts including the CRT.
Eventually I went and got one of the senior guys, he looked over my bench for a few minutes then reached over and turned off my new desolder station . Problem solved. The stray mag field from the transformer was doing it all along.

We both agreed to keep quiet about it, I don't think the company made much profit on that one...

 

[The Artilleryman]

What genius decided to use aluminium bolts to hold the electrics onto the steering rack for a UK spec. Mondeo (2015 - 2016).
Now a major recall to fit steel bolts, but quite a few alloy bolts snap when being undone - now needs a new steering rack and at least a 6 week wait without a car - not a Ford design this time but Bosch.

Luckily mines a 2018, so should have escaped this disaster.

 

[Morrisman]

Bulbs checked, switch checked, jumpered across the connector, still no reverse lights.

A place in Stoke is getting me a new plug and play BCM, only downside is it's £250

But as long as I can keep me old faithful Mondeo alive for a few more years I'll be happy.

Some people pay £250 a year just for their road tax, whereas mines £30.

 

[dobbslc]

£250 a year tax would be cheaper than mine!

 

[prepman]

£250 a year tax would be cheaper than mine!

Same here...£320 it is