Hi volvo fans,

I have a 2006 Volvo S40, it is a beautiful car, while I am struggling with some electrical problems.....

The ignition switch fuse keeps blowing (fuse 26 15 amp fuse) every time when I turn my key to position II (the accessory position), I have not even reached position III (the ignition and start position).

to limit where is the problem, I have pulled all fuses in the main fuse box and removed the CEM box,

it still blows when I turn my key to position II (the accessory position)......

any ideas what is happening ?

 

its either shorting inside the switch or on one of the output circuits which are energized with the key in position 2. At this point you probably need to start probing at the connectors to see which of the 12v terminal/pins show low resistance to ground when you go from off to position 2 or which carry voltage show ground with the key is off.

 

The way I like to troubleshoot problems like this is to wire a large 12 volt lamp (heavy duty tail light or even a headlight) with leads, and push the leads into the fuse connections. That way, if there's a dead short on the circuit the fuse protects, all that happens is that the lamp lights up (no fuses blow, nothing is stressed). Then start looking for the items that are powered on that circuit and start unplugging them one at a time. When the lamp goes out, you've found your culprit! Also, if the problem is intermittent (like a wiring harness laying against a ground with the insulation worn through), wiggling it will make the lamp go on and off.

I wish Volvo had a "real manual" so we could give you more info on what's likely on that fuse - the best you can do is check your owner's manual to see what that fuse protects.

 

thanks for this detailed method, i figured out the CEM is corroded, since then I have used some contact cleaner to clean.
once i put it back,
there is no dashboard lights and
once i turn key to position II or III, no dashboard lights, no crank, but something under engine has a strange sound (sounds like a dancing dolphin)...

if you would not mind, do you have any ideas what happened?

 

thanks for this quick, cost-efftective method, it is a combination of old school and new technology, this is art!

i figured out the CEM is corroded, since then I have used some contact cleaner to clean.
once i put it back,
there is no dashboard lights and
once i turn key to position II or III, no dashboard lights, no crank, but something under engine has a strange sound (sounds like a dancing dolphin)...

if you would not mind, do you have any ideas what happened?

 

If I'm reading your post correctly, the sequence went like this...

1) there was "something" wrong with the car, but it was running
2) you pulled the CEM and cleaned it, and reinstalled it
3) the car won't start / dash won't light up

If that's the case, it would have been a really (!) good idea to include it with the original post. Otherwise it's "my face just caved in - does anyone know why" - then 12 posts later - "oh yeah, I did fall off a ladder"... ;-)

If my hypothesis above is correct, then it's almost certainly something you screwed up reinstalling the CEM. There are a LOT of connections that can get messed up - maybe one of those long, fragile, skinny pins got bent down? I'd suggest taking it all back apart and going over it all with the proverbial fine tooth comb to see where the short is. I'll bet you find it there.

 

thanks habbyguy, haha, I like your example and it made me laugh.
thanks for your ideas, yes I will go over and have a look again

 

well that update makes your next step a whole lot easier. Disconnect the CEM connectors, turn the key, check the fuse... :-)

 

thanks for your kind words, yes

i find there is a pink colored wire (a very thin 1 mm wire) was cut off when i remove the CEM and this makes the short.
I might need a proper solder to fix the broken wire.