240 General: New (to me) 1980 Volvo 244

[360beast]

Originally Posted by Laird Scooby

I'm surprised the 940 BFU monitors the headlamps Luke but as Alan suggests and as i told you last night, the BFU is looking for balance between left and right so as long as the two LED headlamp bulbs draw the same current then the BFU lamp will remain off. Also did you switch to headlamps and not just sidelights? On dim-dip it may cause more of a problem than normal dip.

I'd say try the LED headlamp bulbs before deciding the BFU is triggered by them

Thanks Dave, I have sent that place you linked to in WhatsApp an email to see if they think it will trigger the BFU.

Yeah I tried the lights on all positions and it stayed on in every position. How come the brake lights need resistance for LEDs? Something in the back of my mind says you or David put LED brake lights in and kept the high level light along with the spoiler brake light in his saloon.

[Othen]

Originally Posted by Laird Scooby

I'm surprised the 940 BFU monitors the headlamps Luke but as Alan suggests and as i told you last night, the BFU is looking for balance between left and right so as long as the two LED headlamp bulbs draw the same current then the BFU lamp will remain off. Also did you switch to headlamps and not just sidelights? On dim-dip it may cause more of a problem than normal dip.

I'd say try the LED headlamp bulbs before deciding the BFU is triggered by them

If it is the same arrangement as the 240, then it is even more crude than that Dave. This is the internal wiring for the unit in a 1980s 240 (same as above):



... so as long as the left and right side bulbs are drawing about the same current it won't trip. I tried this yesterday with one LED and one halogen bulb fitted. The halogen was drawing about 5A (60w) and the LED perhaps 1-2A (I don't really believe the 30W rating, that is just to keep people happy), but I still didn't get an error message. The tolerance of the little inductance switch is obviously quite large (at least a factor of 5 I'd say). As long as there is a circuit both sides there probably won't be an error.

:-)

[BicycleBoy]

Originally Posted by 360beast

https://classicandsportscar.com/news...s-legal-or-not

No mention that Alan has to use E marked bulbs in his car because the headlights are E marked.

Here's the relevant notice you might want for the MOT:

https://www.gov.uk/government/public...mp-conversions

It appears that ALL motorcyclists and pre April '86 cars have now been granted an exemption since March 2021.

[Laird Scooby]

Originally Posted by 360beast

Thanks Dave, I have sent that place you linked to in WhatsApp an email to see if they think it will trigger the BFU.

Yeah I tried the lights on all positions and it stayed on in every position. How come the brake lights need resistance for LEDs? Something in the back of my mind says you or David put LED brake lights in and kept the high level light along with the spoiler brake light in his saloon.

The LEDs shouldn't trigger the BFU as long as they draw similar current Luke, the only time maybe would be on dim-dip as that feeds both bulbs through dropper resistors. The arrangement for David was a one-off because he not only had the OE high level stop light in the rear window but added a spoiler with a built in LED brake light. The way the BFU is set up is it has two coils of wire round one reed switch. Normally there is similar current in each coil and they are wound in opposite directions so the magnetic field one produces is cancelled by the other coil resulting in no operation of the reed switch inside the coils. If one bulb fails, only one coil produces a magnetic field, operating the reed switch.
On the brake light circuit, the left side (that ffeeds the left and high brake lights) only has half the number of coils of the right hand side, resulting in needing twice as much current to produce the same number of Teslas (the unit of magnetic flux, took over from the Weber) as the the coil feeding the single bulb. Because David was effectively feeding two high level brake lights from the same feed as the original, we had to load something with resistors, can't remember exactly what now but it was quite protracted working it all out.

Originally Posted by Othen

If it is the same arrangement as the 240, then it is even more crude than that Dave. This is the internal wiring for the unit in a 1980s 240 (same as above):



... so as long as the left and right side bulbs are drawing about the same current it won't trip. I tried this yesterday with one LED and one halogen bulb fitted. The halogen was drawing about 5A (60w) and the LED perhaps 1-2A (I don't really believe the 30W rating, that is just to keep people happy), but I still didn't get an error message. The tolerance of the little inductance switch is obviously quite large (at least a factor of 5 I'd say). As long as there is a circuit both sides there probably won't be an error.

:-)

There isn't as much leeway as you'd think Alan, even two brand new bulbs from the same box can cause an imbalance in the magnetic flux intensities. See my description of the BFU operation above ^^^^^

There is some tolerance on the reeed switch but surprisingly not much.

[Othen]

Originally Posted by BicycleBoy

Here's the relevant notice you might want for the MOT:

https://www.gov.uk/government/public...mp-conversions

It appears that ALL motorcyclists and pre April '86 cars have now been granted an exemption since March 2021.

Ah ha! That explains why none of my biker mates have any issues with LEDs on their motorcycles.

That is also good news for the Barge and perhaps GAM as well. If this eve's test drive goes well and I'm happy they are safe and useful, I may order two more pairs of bulbs to fit out GAM, my Triumph and Royal Enfield (I'll check, but I think they are all H4, which is convenient).

:-)

[Othen]

Originally Posted by Laird Scooby

... There isn't as much leeway as you'd think Alan, even two brand new bulbs from the same box can cause an imbalance in the magnetic flux intensities. See my description of the BFU operation above ^^^^^

There is some tolerance on the reeed switch but surprisingly not much.

Maybe Dave, but my empirical test with one LED and another halogen bulb would tend to suggest otherwise.

:-)

[Laird Scooby]

Originally Posted by Othen

Maybe Dave, but my empirical test with one LED and another halogen bulb would tend to suggest otherwise.

:-)

I don't think the 240 BFU monitors the headlamps Alan, same as i thought the 7/9xx didn't, however it appears my 760 does and Lukes 940 does whereas my previous 740s didn't. I know they changed the BFU some time in the mid-late 80s so perhaps why.
That said, looking at the diagram of your BFU, it shows connections for dipped beam (lower beam as they call it) so maybe your BFU is faulty or bypassed on that circuit.

[360beast]

I've unplugged both headlights and the BFU doesn't light up on any position so as Dave suspected it is measuring a voltage difference not resistance.

I only ever have my headlights in the driving lights (off position) or the headlights on position as the sidelights means they stay on with the ignition off and my dim dip doesn't appear to make the sidelights any brighter so I never use it.

[Othen]

I’ve just taken the Barge for a short test run in the dark. The headlamps have gone from being mediocre (by modern standards) to good. They aren’t as bright as the xenon lights on the Skoda, but they produce more light than average. The biggest difference is the colour of the light - much whiter and I think therefore far safer (both seeing and being seen).

I think this is a good upgrade. I may turn the aim down just a fraction.

Alan

PS. Does anyone happen to know which knob is the vertical adjuster (and by elimination which does the horizontal)?

[Othen]

Originally Posted by Othen

I’ve just taken the Barge for a short test run in the dark. The headlamps have gone from being mediocre (by modern standards) to good. They aren’t as bright as the xenon lights on the Skoda, but they produce more light than average. The biggest difference is the colour of the light - much whiter and I think therefore far safer (both seeing and being seen).

I think this is a good upgrade. I may turn the aim down just a fraction.

Alan

PS. Does anyone happen to know which knob is the vertical adjuster (and by elimination which does the horizontal)?

... and the answer is: the bottom knob does the up and down, the top one adjusts left and right.