Battery polarity foul up - Urgent help needed.

From CEM to VEM, from LED to lightbulb and more. If you have an electrical problem, like a broken info-centre, search for answers in this category. This is also the place to be when you expect the problem to be of an electrical nature...

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yorkshire480
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Battery polarity foul up - Urgent help needed.

Post by yorkshire480 » Thu Jan 21, 2016 1:26 pm

After a spell in hospital I came home to find my 94 ES with a flat battery. One recovery jump start later it's apparent the battery is goosed.
To my eternal shame whilst fitting the replacement I managed to connect it up the wrong way round. I'm blaming all the drugs they've put me on - my head is a shed and I'm still physically weak.

Whilst connected up incorrectly the horn alarm sounded, drivers side window went down and the sun roof opened. Having realised my mistake I hooked it up correctly.

On ignition the engine started up but was quickly very lumpy and now won't start at all. The info centre has power however the LED segments don't light up but warnings such door open, washer fluid level do.
Central locking, alarm light, windows all work.

I've pulled fuses but can't find any burnt out ones.

I've a horrible feeling I've fried the ECU hence the engine quickly giving up for lack of control. The missing data to the info centre suggests this to me also.

I'm absolutely besides myself for such a stupid mistake and I fear I've really gone and done it this time. :badmood:

Please 480 guru's please help me out here. :nuts: :nuts: :nuts: :nuts:

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Re: Battery polarity fowl up - Urgent help needed.

Post by brinkie » Thu Jan 21, 2016 1:50 pm

The sensitive electronics are all protected against reversed polarity. They have a 5 volt supply rail, which is generated by an internal voltage regulator that brings anything between 8 and 16 volts down to 5. The inputs are protected against wrong polarization.

All computers in your 480 work separately and independently. They have only contact with each other through analog sources (voltages, currents). So if one dies, the other shouldn't be affected other than giving or receiving wrong data. The inputs are protected as well. Yesterday I was fiddling around with an info centre and accidentally put 12V on an input that should be grounded, the power supply started to hum (indicating a LOT of current) and the info centre didn't die.

Central locking, windows and alarm light are all controlled by CEM, so that one has survived. The engine did start, so the ECU didn't die either.
What could be broken, is the idle control in the ECU. Try and start the engine with a little bit of throttle.

The info centre isn't a LED, it's an LCD (Liquid Crystal Display), that's why it needs a light source. Shine on the dashboard with a small torch, if you see the fuel segments, then it's only the halogen bulb that has died. If you see a dim green light from behind and the display is blank, it might indeed have died. But the engine doesn't need the info centre to run.
Robert.

Present cars: 1994 Volvo 480 GT 2.0i Vase Green, 2010 Volvo V70 2.0F Momentum Mystic Silver
Past: 1981 Talbot-Matra Murena 2.2 Rouge Mephisto, 1995 Volvo 480 GT 2.0i Paris Blue

Norm57
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Re: Battery polarity fowl up - Urgent help needed.

Post by Norm57 » Thu Jan 21, 2016 2:37 pm

Hi if you need a ecu i can help you i am breaking one of my celebrations its a 95 auto i am in leeds so let me know also may have some other bits and pieces

yorkshire480
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Re: Battery polarity fowl up - Urgent help needed.

Post by yorkshire480 » Thu Jan 21, 2016 3:07 pm

Thanks for the wonderfully detailed and speedy information.

Sure enough she starts up given some throttle. The revs race away up to 3000 and then settle back to 1100 quickly.
Looking at the LCD with a flashlight I can't see any segments and there seems to be some backlight so I'm guessing it's something other than halogen bulb having blown.

Norm57 - I'll pm you as seems likely I'm going to need to take you up on your kind offer!

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glasgowjim
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Re: Battery polarity fowl up - Urgent help needed.

Post by glasgowjim » Thu Jan 21, 2016 5:46 pm

Be aware that the 1.7 and the 2 ltr have different ECUS.

Before getting a replacement ECU note down the numbers on the front of the unit and make sure the replacement has the same numbers

the reason I say this is ..

B20F engine ECU pn 472948/03 seimens s111702102

engine ECU for B20F engine pn 472948/02 seimens s111702102 B

not cutting across anyones sale

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Re: Battery polarity fowl up - Urgent help needed.

Post by yorkshire480 » Thu Jan 21, 2016 6:06 pm

Cheers Jim.

So for the sake of clarity.

Thus far it's looking like I need a replacement ECU (that's the one found in the passenger side footwell right?)
and a replacement info center.

It's been a while since I had an info center apart. How doable is transplanting the LCD elements from a donor?

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Re: Battery polarity fowl up - Urgent help needed.

Post by glasgowjim » Thu Jan 21, 2016 6:55 pm

The CEM is at the left hand side of the passenger footwell . (assuming a RHD car) You dont need that one replaced .
The ECu is at the right hand side of the drivers footwell and is "silver metal" coloured.

changing the LCD display is easy .

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Re: Battery polarity fowl up - Urgent help needed.

Post by Alan 480 » Thu Jan 21, 2016 6:57 pm

yorkshire480 wrote:Cheers Jim.

It's been a while since I had an info center apart. How doable is transplanting the LCD elements from a donor?
AFIK doddle :-)

just swap the unit across it is a separate unit from the rev counter and speedo, ie there are THREE units in the inst cluster, I can't even remember if the spare I have is 1.7 or 2litre but seems to be the same. might have a wee issue with the fuel tank level?

note that there is 'back lighting' and a SPECIAL bulb for the info centre, go and look at the unit in the dark, it might be 'just-visible' using the torch or even now it is fully dark. much easir than taking it apart!

engine managemnet is a different kettle of fish
Alan

480 ES 2litre x 2, C30 1.8ES, SS1

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glasgowjim
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Re: Battery polarity fowl up - Urgent help needed.

Post by glasgowjim » Thu Jan 21, 2016 6:58 pm

Swapping over ECu is again rather straightforward.

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Re: Battery polarity fowl up - Urgent help needed.

Post by Alan 480 » Thu Jan 21, 2016 7:11 pm

glasgowjim wrote:Swapping over ECu is again rather straightforward.
Jim, sorry didn't explain that clearly, easy to do the swap as seem to recall just a couple of self tappers and a multi plug?

BUT must be compatible part number, don't think the LCD is engine specific
Alan

480 ES 2litre x 2, C30 1.8ES, SS1

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Re: Battery polarity fowl up - Urgent help needed.

Post by yorkshire480 » Thu Jan 21, 2016 7:31 pm

Okay so it would seem the first course of action is to remove the ECU and get a part number for it. They seem to be fairly readily available.
Then it's sourcing a suitable info centre donor I guess.

Looks like it's gonna be an uncomfortable Friday for me!

I'll go and have another look at the LCD's now it's dark. Presumably I can check the state of the halogen backlight by using the brightness adjustment wheel.

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Re: Battery polarity fowl up - Urgent help needed.

Post by glasgowjim » Thu Jan 21, 2016 8:17 pm

I have an info centre display unit spare :D

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Re: Battery polarity fowl up - Urgent help needed.

Post by yorkshire480 » Fri Jan 22, 2016 2:43 pm

Well I'm kinda stumped removing the ECU. Removing the trim no problem. I can feel the connector but
for the life of me can't find the oft mentioned two screws holding it in either by touch or with aid of phone video.

This is what I'm looking at
Image
Image

Clues appreciated! What am I missing?

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Re: Battery polarity foul up - Urgent help needed.

Post by yorkshire480 » Sun Jan 24, 2016 3:44 pm

Well I finally got the bugger out with aid of a stubby screwdriver that had cut down even further in order to gain access!

I may have sourced a replacement already - hopefully they're a match.

Image

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Re: Battery polarity foul up - Urgent help needed.

Post by Alan 480 » Tue Jan 26, 2016 12:55 pm

when you put it back in, leave the screw at front 'just tight so you can maybe slide the unit in easier.

I do like the fact that the version 'C' has 20F on the label as well, saves ANY ambiguity, which is odd as normally you need a cross reference sheet (or two) :-)
Alan

480 ES 2litre x 2, C30 1.8ES, SS1

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Re: Battery polarity foul up - Urgent help needed.

Post by yorkshire480 » Fri Jan 29, 2016 4:15 pm

Okay.....the saga continues.

The replacement ECU is in and all seems well with the engine. The LCD module however.... :cry:

The replacement cluster Norm gave me is an exact match for mine so all good there. Due to various issues surrounding previous repairs to my cluster I decided the best option was to use the PCB, the LCD section and rev counter from the newer donated cluster. That way I can keep original mileage and to be honest the PCB looked in better nick than mine.
Having inspected the PCB for dry joints and perused the ribbon connector (again it's in better condition than mine) I assembled a new cluster and loaded it with bulbs testing them as I went.

Putting the rebuilt cluster back in the car still no LCD gauge. Halogens are ok. I can see them illuminate and they're warm when I remove them. The car drives fine and speedo and rev counter are both working. At this point I begin to suspect the fault is elsewhere.
:(
Having searched the forum I see mention of the MFU that is housed from what can gather in the PCB that piggybacks onto the rear of the cluster. Consulting photos I realise I've used the one that was one the car originally. However swapping it for the new one yields the same results.
Is the MFU actually on PCB section of the speedo section? My next logical step is to try the donated speedo module which I'll do tomorrow.

So come on 480 gurus. Where else should I be looking? As I say, I can't help thinking the problem isn't in LCD module.


Sidenote: my mechanic did a speedo repair some years back which has worked ever since. It involves drilling out the lower right hand side connector of the connector block and hard wiring a connection wire through the hole and soldering it to the receiving pin. Then at the other side of the block soldering onto the loom wire. I had to replicate this but opted for screwblock connector instead knowing that I'd probably have to take it off again soon!

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Re: Battery polarity foul up - Urgent help needed.

Post by Ade » Sun Jan 31, 2016 1:59 am

This is probably a long shot but I'll throw it into the mix anyway....

There is an earth somewhere near to (in the case of my turbo) or actually to (in the case of a 2.0 that I knew) the alternator, without which the info centre does not work. I discovered this when I put my engine back in after changing the clutch as I mysteriously had no info centre on initial start up and with a little poking around I found a little brown wire that I had neglected to reconnect. Once reconnected it worked fine again. Just wondering whether having the battery on backwards could have fried this earth (or something related to it if it goes to your alternator), it is a very small guage cable and normally would only carry a tiny amount of current. Still scratching my head wondering if/how having the battery arse about face might subject small earths to a higher current........ If the body/engine etc suddenly have the + charge and its able to find its way back to earth the wrong way, you might have a higher current through these little earths right? Maybe!? Help!

Just a thought, something to have a look at, any input appreciated as always. I might be talking complete bollocks...... I'm not exactly an electrical expert, I have a working knowledge sufficient to keep old cars going which I kind of add to/refine with each new electrical problem posed by my 480! The longer I own it, the more proficient I become at interpreting wiring diagrams, fault finding and excommunicating then circumventing the CEM from stuff that it won't let work anymore! The car that gives something back, forget doing an electronics course, just buy a 480. Probably cheaper too, and more fun :)


:kill: CEM
O.C. 480 D.

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