Nearly but not quite

[ukkid35]

I thought I was going to get a full year of trouble free fun in the Cerb, and it was going so well until Monday evening

At 10pm I started to head off for track days at Spa and the Ring, but after going over a speed bump (at walking pace) where I live the head lights started flickering

Last year I was able to fix the same problem by reflowing the solder in the headlight relay box, this time it made no difference

The symptoms have settled down now, because previously the flickering was intermittent, but now they are predictable and constant:

Flickering on Dipped Beam only, and only when the engine is running

I can feel and hear the relay (or relays) pulsing when the lights are flickering

I had a look at the wiring diagram for the connections to the relay box but can't make head nor tail of it

A4 Dip Beam
A6 Battery (Dip)
B4 Dip Beam Sig

Nothing is marked Earth
There are two Main Beam, B8 and B9
There is only one Dip Beam A4, why?

If I could have worked out how to jumper the relevant relay(s), I would have been able to drive the Cerb

Instead I'm at Spa in my other car

Any thoughts on what the underlying cause is, and also what could I have done as a workaround?

[Flatplane8]

Hi,

Not sure if this helps, but the headlight control box has a 'dim-dip' function which is designed to supply the main headlight bulbs with low voltage when the sidelights only are on. I've wired in my headlights with heavier cable direct to the battery using relays to switch them, the TVR wiring just triggers the relays now.

I discovered the dim-dip function when doing this as it would cause the relays to buzz, maybe thats part of the issue? After some research I simply cut the wire for the dim-dip function and that fixed my problem.

Simon

[ukkid35]

Thanks - I forgot to mention that I removed the Dim-Dip box ages ago, following some advice that was shared here

[Gladers01]

ukkid35 said:

I thought I was going to get a full year of trouble free fun in the Cerb, and it was going so well until Monday evening

At 10pm I started to head off for track days at Spa and the Ring, but after going over a speed bump (at walking pace) where I live the head lights started flickering

Last year I was able to fix the same problem by reflowing the solder in the headlight relay box, this time it made no difference

The symptoms have settled down now, because previously the flickering was intermittent, but now they are predictable and constant:

Flickering on Dipped Beam only, and only when the engine is running

I can feel and hear the relay (or relays) pulsing when the lights are flickering

I had a look at the wiring diagram for the connections to the relay box but can't make head nor tail of it

A4 Dip Beam
A6 Battery (Dip)
B4 Dip Beam Sig

Nothing is marked Earth
There are two Main Beam, B8 and B9
There is only one Dip Beam A4, why?

If I could have worked out how to jumper the relevant relay(s), I would have been able to drive the Cerb

Instead I'm at Spa in my other car

Any thoughts on what the underlying cause is, and also what could I have done as a workaround?

You could try bridging A6 to A4 to bypass the suspect relay, also check the voltage is stable at +12v or 0v at A6 and A7 and not floating somewhere in between causing the relay to chatter.

The B8 and B9 are 2 relay outputs supplying power to the higher wattage (higher current drawn) main beam bulbs, whereas the dip beam only has one output A4 to supply both bulbs

[Juddder]

Hey Paul

The ones to look at are:

A8 - Battery (Main) (+12V supply)
B5 - Main Beam Sig (on/off)
B8 - Main Beam (output)
B9 - Main Beam (output)

If either A8 or B5 have a loose connection somewhere or a kink in the wire, then you will get the relays bouncing on and off which will cause B8 and B9 to flicker on and off

I'm away from my car at the moment but happy to do any tests you need to check etc.

Alex

[ukkid35]

Thank you both, very helpful

I was confused by the two outputs for main and one for dip because standard H4 are 60/55W, which doesn't seem like a big difference

I know you can fit 100W H4, but they are typically 100/90W, not a big difference, although of course I would never risk trying that in a TVR

[Gladers01]

ukkid35 said:

Thank you both, very helpful

I was confused by the two outputs for main and one for dip because standard H4 are 60/55W, which doesn't seem like a big difference

I know you can fit 100W H4, but they are typically 100/90W, not a big difference, although of course I would never risk trying that in a TVR

It's a strange one for sure, even at 55W/12V the current draw would be nearly 5 amps per bulb, by using only one output the relay would be on the limit, they would have been better off using 2 relay outputs as per the main beam, another thing to check is the condition of the contacts on the suspect relay, if they're pitted or reading a high resistance you may be able to swap it out with the unused sidelight relay

[ukkid35]

Gladers01 said:

It's a strange one for sure, even at 55W/12V the current draw would be nearly 5 amps per bulb, by using only one output the relay would be on the limit, they would have been better off using 2 relay outputs as per the main beam, another thing to check is the condition of the contacts on the suspect relay, if they're pitted or reading a high resistance you may be able to swap it out with the unused sidelight relay

I do have a couple of new relays that I bought a couple of years ago when the box originally went wrong

I wonder whether I'll be able to find them...

[ukkid35]

This is all I would have needed to do to use my Cerb back in October



The red jumper gives me dipped headlights

The black jumper gives me front and rear side lights

This does not correspond to any pinout that I've seen

My car is a 4.5 98, who knows whether that makes any difference

I'm now carrying jumpers for this, just in case

[ukkid35]

One of the relays was really suffering, so I de-soldered it and replaced it with a new relay





Sadly I damaged one of the tracks so I had to add a jumper



Tested and working well, when the ignition is on, when the engine is running, and also tested when driving over speed bumps

Very happy with the result

[Luckyone]

ukkid35 said:

One of the relays was really suffering,

The relay for the starter motor has been causing me a huge number of headaches.

I think you may have added one in yourself for your starter?

Some Cerbs already have one fitted by the factory down in the passenger footwell, it takes power from the big fuse that is also hidden up in the passenger footwell, good idea when the relay works 100% of the time….

[FarmyardPants]

Especially since the starter can draw a few hundred amps! I would expect a regular automotive relay to turn into a marshmallow

[ukkid35]

FarmyardPants said:

Especially since the starter can draw a few hundred amps! I would expect a regular automotive relay to turn into a marshmallow

The starter relay only has to power the solenoid, rather than the starter itself, even so I think it draws about 25A initially, then only half that on 'hold' when only one coil is energised

[Luckyone]

ukkid35 said:

when only one coil is energised

Bugger, you knew about that then?!

I wish I’d come on here to ask about the starter solenoid before buying a new one now (in too much of a hurry to get it working). I didn’t realise jt had duel coils so assumed it was broken when testing it off the car. It wasn’t till I was testing the new solenoid I realised it needs the main battery terminal connected up too when you’re touching the solenoid to +ve.

I think the starter was fine all along, seems it was just that little normal relay inside the car causing my issues.

Intermittent faults are such fun….

[ukkid35]

Luckyone said:

Bugger, you knew about that then?!

I wish I’d come on here to ask about the starter solenoid before buying a new one now (in too much of a hurry to get it working). I didn’t realise jt had duel coils so assumed it was broken when testing it off the car. It wasn’t till I was testing the new solenoid I realised it needs the main battery terminal connected up too when you’re touching the solenoid to +ve.

I think the starter was fine all along, seems it was just that little normal relay inside the car causing my issues.

Intermittent faults are such fun….

Yes, I found out the hard way, ended up driving home from Germany without a starter motor



https://www.pistonheads.com/gassing/topic.asp?h=0&...

I now carry a spare starter motor at all times

Edited by ukkid35 on Sunday 3rd March 06:01