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 96 V4 - Main Beam Wire Pick-up Point
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SAAB96L
V4 Mad

United Kingdom
518 Posts

Posted - 01 Apr 2024 :  16:31:45 Show Profile Reply with Quote
Hello.

I'm looking to pick-up a feed from the Main Beam wire at the lighting relay; the reason being is to supply power for auxiliary lamps.

Looking at the wiring diagram in the WSM and also the useful A3 colour wiring diagram I cannot ascertain which of the connections on the lighting relay [30, 86, 5, F, 56a] supplies power for the main beam.

Currently my money is on connection 5 OR 56a.
F appears to be for the main beam warning light.
30 is the main feed to the unit from the fuse box.
86 seems to be the wire from the headlight switch to the lighting relay.

If anyone can confirm which is the connection, I will be most grateful.

The attached link is an excellent wire tracer, but I'm still not sure.

http://www.saab-v4.co.uk/speedball/topic.asp?TOPIC_ID=39676&SearchTerms=lighting,relay

Thank you.

Richard.

beardydave
V4 Fan

133 Posts

Posted - 01 Apr 2024 :  19:02:26 Show Profile Reply with Quote
Search H4 wiring on the interweb, that gives the pinout for the connector. I think it will be the rh wire with the centre one at the top.
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SAAB96L
V4 Mad

United Kingdom
518 Posts

Posted - 01 Apr 2024 :  19:52:40 Show Profile Reply with Quote
Thanks for getting back to me, much appreciated.

That's not where I want to pick the feed up from, as per my opening post - it's at the lighting relay source.

Regards.

Richard.
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beardydave
V4 Fan

133 Posts

Posted - 02 Apr 2024 :  08:04:22 Show Profile Reply with Quote
Do you mean the power feed upstream of the relay? Or the output from the switch to the relay coil?
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SAAB96L
V4 Mad

United Kingdom
518 Posts

Posted - 02 Apr 2024 :  08:46:50 Show Profile Reply with Quote
I'm trying to ID the wire that connects to the relay which provides power to the main beam.

It's probably going to be a process of elimination by wire removal & refit on the relay.

I need the aux lighting to illuminate when main beam is selected and extinguish going to dipped. There will also be a switch that isolates the aux lighting from main beam activation if required.

That's my goal, albeit I'm not back in the garage until end of the week - hence no rush.

Regards.

Richard.
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beardydave
V4 Fan

133 Posts

Posted - 02 Apr 2024 :  09:53:51 Show Profile Reply with Quote
5 is trigger from the switch to the relay for main beam, the switch grounds the relay using power from 30
56a is the power from the relay through fuses 11 and 12 for the main beam.

Difficult to add in extra lights on the main beam if youre wanting to also have them isolatable.

Without the isolation you can just stick the relay inline on the 56a wire before the fuse box, and pull a clean fused power from somewhere to power the aux lights. The relay coil won't drop the power to the main beam much, but running the aux lights directly from the 56a might overload the relay. If the aux lights relay fails you'll loose all main beam lights.

With isolation the only way I can think of would be to take the power from the aux relay and run it into the cabin through a switch rated for the power, and back out again. Not a fan of switches on full power wires in the cabin myself.
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andydeans3
V4 Guru

United Kingdom
2016 Posts

Posted - 02 Apr 2024 :  11:33:26 Show Profile Reply with Quote
Richard
I did this for the spots on my blue Saab. I'll be out in the garage later today, I'll have a look later when I'm in the gaarge agin.

You could also just tap into the main beam feed down near the headlights, feed it through a switch inside around your dashboard, and use that to trip a relay, that takes its power feed from the bank of 4 fuses, that go live with the igntion. Feed that power to the headlights

I renewed all the feed wires, (Plus the plug on the back of the bulbs) ,to main beam with new, heavier cables, as well as the earth lines to the main beam.

In fact I went one step further, having tapped in to the lighting relay for the main beam out, I used that feed, to trip another relay, to take power to the main beams. This takes electrical strain off the lighting relay, since the power going through it to power main beam is only tripping a relay, rather than supplying all the current to the meain beam filaments.


1978 LHD SAAB 96,1975 96
1978 MGB Roadster
2008 LHD "Classic" Renault Twingo
1991 Nissan Figaro

Edited by - andydeans3 on 03 Apr 2024 01:48:53
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SAAB96L
V4 Mad

United Kingdom
518 Posts

Posted - 02 Apr 2024 :  18:16:33 Show Profile Reply with Quote
Many thanks Dave and and Andy.

Dave - The breakdown you have given is very useful and makes sense. I agree fully with your last sentence about the switch taking the brunt of the electrical load. That will not be the case here.

Andy - That's brilliant if you can have a look, I will be most grateful.

What I'm looking to do is to spur off the main beam wire to feed the auxiliary 5-pin relay. Of note the connections 30 and 87 will be swapped around so that I can use the 2x 87 relay spade terminals to feed the lamps - one number to each.

The diagram below gives the set-up which also shows how the switch is incorporated to isolate the aux lighting, if not required when the main beams are used.

Regards.

Richard.




Edited by - SAAB96L on 03 Apr 2024 17:16:54
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beardydave
V4 Fan

133 Posts

Posted - 02 Apr 2024 :  23:48:14 Show Profile Reply with Quote
Only problem with that is that the relay coil will have much less resistance than the main beam bulbs, so would cause almost a short circuit. Putting a big ballast resistor in there would only cause the main beams to dim.

As Andy said, better to have the 56a trigger 2 relays, one to to main beam and the other for the spots. No problems with imbalances, the power for the main beams is taken away from the headlamp relay reducing the load on that, and you can keep a switch before the coil on the spot relay for isolation.

Means more re-wiring of the original wires, but a much safer setup IMO.
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SAAB96L
V4 Mad

United Kingdom
518 Posts

Posted - 03 Apr 2024 :  17:45:28 Show Profile Reply with Quote
Thanks Dave, the info is appreciated as always.

I was having a trawl through some old threads on this Forum and found this flagged by Woody in August 2010:

I have taken a feed from the "F" terminal on the head light relay to terminal 86 on a smaller SWF relay. Power to the spots relay (terminal 30/S1) comes via auxiliary fuses fed from the main fuse board. Terminal 87 is the feed to the spots. Terminal 85 is the earth which goes to a pull switch on the dash and then to earth.

It's an avenue I need to explore and echoes my initial train of thought that "5" may provide the feed opportunity. The feed is just to open the relay, so it can allow the relay to power the spots.

Regards.

Richard.
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