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Relay will not stay in - ideas?

Andy Green

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The other day as I left work it was getting dark. So headlights on. No joy. They worked on main beam but not dip. Not that dark and only 3 miles home so got home on sidelights OK.


So at the weekend changed the fuse. Headlights now work fine again. Tested old fuse which is OK, so I put it back in, still worked so I assumed that the fuse had not been seated correctly from new. So job done.


Headlights not working again during come mist on an early morning blat yesterday.


Had another play and wiggling the fuse made it work. After a while it was clear it was the relay that was the issue. Swopped relay with one of the others and still have the problem. Wiggled wires into back of fuse/relay box and that does not seem to be the issue.


If I put a little pressure on the relay they work fine in dipped and main. Sometime they work for a while after removing pressure.


I am off out now and when I get back ill try some contact cleaner in the relay holder.


Any other suggestions that might work. Changing the fuse/relay box is not something I want to start if it is not necessary.


I did notice that the headlight relay was different from the other two. Would you not expect them to be all the same as Caterham only sell one type of relay. I built the car and have never played with any of the wiring,




Car is an 2009 R400 SV Duratec without Stack. So it has 3 relays and the flasher unit in the 5 holder relay box/fuse box. The 3 relays are in the 3 top positions. The headlight one is in the middle of the 3.

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If its the same as earlier relay sockets, the female brass contacts in the socket are crimped onto the wires and pushed in from behind the socket. The contact has a slightly raised tab in the middle of one face that locks it into the moulding. Sometimes these tabs get bent or are not raised enough and can unlock and get pushed out so the relay contact is not being inserted properly and only makes an intermittent connection. Another possibility is that the female connector just needs nipping up a bit if its loose on the relay contact.


Either way, the only way is to undo the screws that mount the socket to the firewall and carefully pull it away. You should then be able to pull out the offending contact and lift the locking tab and then reinsert until it clicks and locks. If its really bu99ered you'll need to get another brass contact, crimp it on and fit it. You can packs of them from any good motor factor for little money or, if you're near Guildford, I've got a box of them.


Unfortunately you may have to lie on your back upside down in the passenger seat to see what you're doing. Make sure you completely disconnect the battery before you do this as its very easy to get a short circuit. I wouldn't just rely on the FIA battery cutout switch if you have one. Also, before you tighten the fixing screws after sorting the problem and are putting the socket moulding back on the firewall, make sure you haven't trapped any wires under the mounting pillars or you'll get a short circuit. Guess how I know that 😳


Edited to add, before you start undoing too much, remove the relay and use a torch to check if one of its socket connectors is visibly different to the others.


Best of luck






Edited by - Paul Deslandes on 20 Nov 2010 12:13:22

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