Indicator stalk relays

[cliftyhanger]

The rotary lightswitch is what switches power (for the headlights, dipped and main) to teh stalk.
The stalk is what changes where that power goes to, either dipped or main (or to confuse matters dipped plus flash!)

Relay, have a look at this:
https://www.youtube.com/watch?v=uUSxo-CCLR8
or
https://www.explainthatstuff.com/howrelayswork.html

all a bit overcomplicated. But a small electric current (ie from a switch) is used to make a relay act like a switch for a larger current.

[Bumpa]

The wiring to the stalk remains untouched. Power still goes from the battery to the rotary light switch then to the stalk. The power coming from the stalk on the blue/white (high beam) and blue/red (dip beam) which used to go straight to the bulbs, now goes to terminals 85 on the relays. The wires are shown on the right side of Tony's diagram.

When you turn on the lights the power flows from the switches to the relays, but all it has to do is energise the electrical switch between 85 and 86, and this closes the contact in the relay. The power for the lamps then passes from your new feed wire (shown red 30) to 87 and to the lamps directly. So no large currents go through the light switches in the car.

When installing the relays you have to cut the blue/white and blue/red wires so that the ends that come from the switches connect to 85, and the ends that go towards the bulbs are connected to 87. 30 is your new high power feed, and 86 is simply an earth.

[HQentity]

Thats great, I think I'm there now. Thanks for the video link Clive!

The only new wires I need are for 30 and 86 - 86 can be 5A wire I guess, but what about the 30 feed? Tony suggested 35A fuses but Steve you think they can be higher?

[Carledo]

The 30 feed needs to be pretty substantial, I would say at least 30 amp to give a safe margin. The 86 earth cable can live on 5 amp as you say. A 35 amp fuse is OK for the dip relay but you really need a 50 amp fuse for the main beam relay.

Steve

[Bumpa]

Here's a photo of the relays on my car, next to the battery. The relays are fused with 20 amp for the high beam and 15 amp for the dip. Steve is right that they ought to be bigger fuses, but I have never had a fuse blow yet. Still, I might put in some bigger ones after this conversation.

You can also see the relay for the starter solenoid. I was having some trouble with trying to operate the starter and nothing happening. I fiited the relay and have no more trouble. That one is a big capacity relay with a 70 amp fuse. Apparently the initial current draw when you turn the key is huge.

Mike

[Jummyboy123]

Hi Guys, where are the relays located for the lo / hi beams ?

[Carledo]

Hi Guys, where are the relays located for the lo / hi beams ?

The standard car doesn't have any!

Experience has taught us that the dipswitch is prone to melting under the load, particularly when Halogen bulbed headlights have been substituted for the original design lower wattage sealed beam units. To get round this potentially dangerous and expensive failure, we recommend fitting relays for the headlights on all Dolomites whether standard or "improved" as it takes the load off the weak dipswitch. Not only is the dipswitch weak, it's also getting increasingly difficult to find suitable replacements, the ones sold by many Triumph specialist suppliers as "Lucas" are actually chinese copies marketed by someone who has bought the rights to the Lucas name only! And good used switches are becoming hens tooth rare. So it makes sense to preserve the existing switches by fitting relays which are readily available and relatively cheap!

Steve

[MIG Wielder]

Well, as promised before Christmas I have done an investigation on the 5in headlight units that can be fitted to the Dolomite.
They are a 37.5 W / 60W brand-new Lucas outer sealed beam unit and a 75W halogen Lucas inner headlamp unit plus an H4 halogen unit.

1-line management summary.( As so loved by Management !)
The running currents switched by the column stalk are reasonable, but the cold switching currents are enormous, only limited by the various wiring resistances.
This is the 75W headlight that some of us have fitted to the inner headlights.

And these are the d.c. characteristics measured with a good DVM and a PSU that unfortunatly was limited to 4A.


This peak switched current of 85 -odd A is per unit and is luckilly limited by the wiring resistance.

I've measured mine. And I measure a drop of 1.30V at a current of 5A. I imagine this is fairly typical of Dolomite wiring.
Which equals 0.26 Ohms. So this will limit the current through the stalk to 25.4 amps for the standard units.
And 32.1 A for the 75W units.

Now to look at the fuse data and determine appropriate fuses.
Tony.