That's a clever idea with little to no downside (except some time spent getting to the CEM, no biggy). Just out of curiosity, why WD40?

How tp open the plastic cover to the cem box?
 

[QUOTE=Russell_S;470421]Hi, I've recently had a headlight problem which, at first, appeared to be the common CEM issue (see this thread http://www.volvoforums.org.uk/showthread.php?t=67437) but finally turned out to be a break in the wiring loom. However, while fault finding the problem I found out a bit about the CEM which I thought others could find useful in faulfinding their own headlight related issues. I've taken a few pictures to help with this.

I have attached to this thread the Volvo wiring diagram for the CEM and headlights because the Haynes manual is worse than useless in this respect as it doesn't even show the CEM in their wiring diagrams.
I have also attached the data sheet for the Fujitsu relays that are used for the headlight switching in the CEM. I originally assumed that they would be solid state relays but in fact they are normal miniature PCB mounting mechanical relays so it they do fail then the data sheet could help find a replacement to repair the CEM.

How did you open the plastic box to the cem unit? i have tried but i could not get it open :/ and how do you replace the relays?

[QUOTE=FunniFir;2202160]There is a single screw that you need to take out in addition to the clips on the side. For me, the screw was hidden under the sticker on the CEM cover.

Apologies for the delay is responding guys, I wasn't getting notifications on this thread.

It's a 2003 1.8 petrol, just getting run it with 150k miles on it. Still getting mid 30s MPG.

Ye, it was the below post from earlier in the thread that gave me the idea, I just said I'd give it a try as an easier/cheaper first fix attempt rather than getting the soldering iron out. WD40 was just what I had to hand, any penetrating oil should work. Just to update, I've since done about 3K miles in it and the lights are still working fine.



It's a delicate job of trying to unclip the clips while stopping them cliping in again as you work your way around. I used two screwdrivers and must admit I cracked two of the plastic clips, but the CEM still went back together fine.

Any alternative for main beam relay?

I'm not sure what you mean by alternative? I've just bought some replacements from RS Components. Ordered online, their part number 3998360, pack of 5, delivered came to £12.68 and arrived next day.

I replaced the faulty one, which now works, but in doing so, it looks like I have upset the working one, so I will need to go back in and either resolder or replace the second one.

EDIT: Looks like you are in Finland, so my suggestion of RS Components might not be that useful - although I think they do accept overseas orders, there is bound to be an equivalent locally that will sell you relays. If you look up the RS Components website and that part number, you should find the specification details of the relay.

In picture there is dipped and main beam relays, is this 3998360 for main or dipped?

Sorry you are correct, mine was for dipped.

I have only parking lights, no dipped, no main beam.
I do herar click from cem with new relays for dipped lights, so I guess light switch is ok.
Also main beam blue light is gloving constantly if I turn light switch to daylight or lights on position. Main beam switch does do notihing.

Any ideas?

Check fuse 12 in the interior fuse box.

It was stupid burned ground connection. Blue light and non clicking main beam relay mislead me
Lesson: loose or lost grounding can make stange things.

Once again, this forum sorts it out....I'd lost the LH dip beam...bulb was OK...so I looked here! Instant diagnosis; ordered a new relay from Poland(!), then took out the module and had a happy time regressing to one of my old persona...electronics technician. Removed the relay and replaced it with new and all was well. A bit fiddly if you haven't done this stuff before, but what a cost effective fix!!! Many thanks to Russell S.....

Same here!
Paid 5€ for parts repairing 600€ new part (CEM modul)!

Big Thanks to all smart and willing to help people on this forum!

Hi although I'm a member of this site I still can't see those photos, can you please repost them , thanks Andy

Hi does anyone know where the boot light on S40 2003 get it's power from as I want to run separate wire because the boot lid wireing loom is plàying up when moved so think I might have a broken wire inside

Wiring diagram here: http://www.matthewsvolvosite.com/dow...03_S40_V40.pdf

Does anyone know where I could source 2 dipped beam relays from? I've tried searching the code on the relay on eBay to no avail and wouldn't know where to start when trying to find one elsewhere.

P1CN012W1

Many thanks, Adrian.

Radiospares/Farnell will have one if you have a pattern , They should be easy to obtain elsewhere too .

There's a place called CPC Farnell near me in Preston which I was considering trying as second in my list tomorrow, an auto electrician is willing to do the replacement for me should I source the part.

That's for the tip!

To anyone looking for relays to replace your old ones, the original relay (P1CN012W1) has been discontinued and is tricky to find. I purchased my relays from RS components for £2 each. The relays I bought are made by Panasonic and it comes up as (JSM1-12V-5) and they have worked on my car.

Yep, I've still got 2 spare if anyone needs one.

Great information in this thread, thank you all!

I had the same issue, no left hand low beam headlights on my recently acquired 03 S40. Replaced new bulb and new fuse and tried this "drill a hole + wd40 quick fix" but no luck. Also tried CRC O2 sensor cleaners and still no light. I guess I have no choice but to solder in new relays?

The WD40 trick may work if the internal contacts are just sticking a bit and the relay is in the early stages of failing. When the relay gets worse and worse, some of the internal contacts get slightly burnt and there will be no current flow, no matter what you try. I have refurbished over a 100 CEMs until now and I have taken all the old relays apart to check where the damage is and what was causing them to stop working. Anyway, new relays are cheap as chips and they are way much more better built than the cheapy original ones

hi just to say thank you, what a fantastic fix. two relays from rs 20 mins start to finish getting old ones out a pain no special tools needed fantastic :teeth_smile:

Does anyone know what the other 2 relays not marked up on the left hand side of the module control

https://www.volvoforums.org.uk/attac...1&d=1539905483

1 Rear window wiper (P1CN012W1)
2 Windshield wiper (P1CN012W1)
3 Main Beams (NH010/01AY)
4 Left dipped beam (P1CN012W1)
5 Right dipped beam (P1CN012W1)
6 Parking light (P3CN012W1)
7 Rear and side marker lights (P3CN012W1)
8 Front fog lamp (56ND12-W1)
9 Rear fog lamp (P3CN012W1)

I would love to be able to download Pdf's on CEM headlight and front beam relays but am unable to do so any suggestions. when I click the pdf's I just get a blank page and nothing else.
Thanks

Teodor Todorov
teotodorov@yahoo.com

same here!:omg_smile:

Me as well
 

Guys seriously, post is great but pdfs are undownloadable... Please upload to a reliable server

Fog Light Hell
 

I appreciate the thread and I'm hoping that I could just get some questions confirmed or clarified. :confused_smile: I have a 2002 s40 that did not come with factory fog lights. After purchasing OEM fog lights and a OEM headlight/fog light switch, I later found out that the CEM needs to be programmed to enable the fog lights. I have read through the thread fully and from what I can see, I can buy a CEM that already has these enabled OR I can have them enabled in my CEM for a hefty price from the dealership. Correct? :thinking: If I do purchase a CEM that is already enabled, are the part numbers the same over here in the US?

Is it possible to just bypass the CEM all together with my own relay and have it wired to the OEM fog light switch? I'm trying to make it look as factory as possible and avoiding an ugly rocker switch mounted under the dash. :Not_Impressed:
I appreciate any help. Thank you!

CEM Wiring/Repair Information
 

Hello everyone,
From Belgium, to thank you for the information published on the forum. Thanks to this information, I was able to repair the CEM by replacing one of the two dipped beam relays.
It works, the work is not very easy and requires patience.
But my 2004 V40 with 341,000km, can ride now at night .... Thanks Alan

Brilliant, well done. Future reference tho, if you replaced one, sometimes easier to swap both out with new ones. Unless it’s only me the second one fails within a week.

I changed both of mine, one had failed and the second one was bulging like the failed one, probably due to fail shortly afterwards. One year and no issues for me yet!

Cem
 

I greatly appreciate your post.
I purchased the Haynes book, and I am very disappointed, in the past I got a BMW Motorcycle book from Haynes, and that one is very detailed.
I knew there had to be some relays for the low beams, and by google I found there was a mention of a CEM....but I could not find the location in the car.
Your pictures above gave me hope...but again, I was confused as it shows right above the gas pedal...in my car is on the extreme left of the dashboard....I realized that you show the British car (I am in the U.S.)... I am happy I found this forum. I find that in the UK you care more for your vehicles. Thank you.

My second one failed a year later.

My dipped beam is out with a good bulb, I suspect the relay.

The P1CN012W1 is a very special animal. High inrush current rating (30A) low coil current (50mA 12V/233Ohm), small size 22x17x17mm, unusual 5 pin layout, Form C.

Tough to find a good substitute. Fujitsu is not making a direct substitute.
I'm thinking the whole design is a folly, judging by their recent offerings in automotive headlight relays.
Zettler AC943 has the same pin-out but less current rating. This may be OK if you can accept a shorter cycle life. If changing to LED headlight is an option then it would be OK. Same goes for the above suggestion.
Incandescent inrush current can be 10x the average current, may cause contact-erosion or -welding.

I'm thinking of remoting the relay(s) to a typical socketed automotive relay. Design wise, putting mechanical relays on a board is a bit "optimistic". Those harness contacts and PCB traces aren't very beefy.
The heat generated from those five relay coils is not going to help the reliability of the semiconductors on the board.

Hi all. This thread is extremely useful. Recently I had both dipped beams just fail on me, with all other lights working OK. I got hold of a used CEM with the same part number and fitted it; however, it isn't working properly. Dipped beams and side lights come on together when you turn the ignition, and on the internal light switch, when the side lights are on, the light indicator on the switch goes out, and when you turn the light switch off the indicator lights up...if that makes sense. Anyway, it would at least appear to confirm that it is indeed a CEM issues as the dipped headlights work!

In another thread, a helpful member said the "VIN" would be wrong even if I get a straight swap for a working CEM. In this thread though, swapping them out seems to be a generally accepted practice. My question is, is there actually any issue at all with swapping them for a CEM that is the same part number?

I have also seen people have unsoldered and soldered new relays for the dipped beam. This is tempting, but I haven't soldered since I was about 12 years old in the school electronics club 🤣 can someone confirm exactly what I will need for this - aside from a soldering iron and solder, please? Any specific iron, too?

Furthermore, does someone have a link for the exact relays that would work?

I have a 2003 V40 Sport 2.0 petrol engine.

The part number of the CEM in there at the minute, and that was working fine, until.recently, is 30621305.

Thank you for any help. It's much appreciated.

Which relay was it that needed fixing so that I can look it up in the company that you recommended for selling relays? Can you post picture too? I'm after relay for o/s/f indicator as mine has stopped working. Everything in lighting works just not o/s/f indicator.