S40 V40: CEM Wiring/Repair Information

[pierremcalpine]

Originally Posted by Joe Soap

Thank you to all the users who posted really helpful information, links and photos. I recently bought a V40 with a non-working left low beam. The bulb worked when tested so an online search lead me here.

Time was against me as I had my NCT (Irish roadworthiness test) booked and would have been charged a fee to alter the booking.

I thought I'd try the easy repair first before ordering new relays. I disassembled the CEM in the car (with the battery disconnected), located the correct relay, drilled a small hole in the lid, squirted a small amount of WD40 in, left it to soak for an hour. It worked, and I now have two working headlights. It may only be a short term fix but it's good to know where to get new relays if I need them.

The car passed it's roadworthiness test, so thanks again to all the helpful users who posted.

(Other work required was replacing a water damaged side impact sensor and clearing the SRS faults, one ball joint which required a new wishbone as some 'genius' had welded the old ball joint in, and two rear brake lines due to corrosion around the fuel tank area.)

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?

[FunniFir]

[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?

[pierremcalpine]

[QUOTE=FunniFir;2202160]

Originally Posted by Russell_S

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?

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.

[Joe Soap]

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

Originally Posted by Muckeroja

Hello just wonder the year of your car mate? thank you Paul

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

Originally Posted by canis

Never heard of this trick before. I'll be sure to keep it in mind.

Originally Posted by pierremcalpine

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?

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.

Originally Posted by Thethompa

Hello.
I had this problem with my right low beam not working. After reading this Most helpfull thread i removed and opened the CEM on my V40-03 2,0T.
I located the relay for right low beam from earlier posts here, drilled VERY GENTLE a 3mm in the plastic cover over the relay, filled it with "oxide remover". Let the remover do its work for ½hour, put the CEM in to the car again...and Yes there was light! If/when the problem comes back i will buy a pair of new relay and change them.
Thanks again for a very helpfull thread!

Originally Posted by FunniFir

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?

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.

[LPR]

Any alternative for main beam relay?

[Worms]

Originally Posted by LPR

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.

[LPR]

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

[Worms]

Originally Posted by LPR

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

Sorry you are correct, mine was for dipped.

[LPR]

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?

[canis]

Check fuse 12 in the interior fuse box.