Classic cars forum & vehicle restoration.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

I will have to study it tomorrow. All this relay stuff has given me a headache! Smile

Peter_L · Posted: Thu Jan 28, 2021 7:38 am Post subject:

Basic wiring diagram for relay/s

The relay coil/actuator only takes very small current. 85-86

The contacts within the relay 30 - 87 (Normally open) take the higher current required by the load, such as a Horn or Lights.

The fuse protects the wiring and relay contacts from damage in the event of a fault/overload in either the load or its associated wiring.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

The diagram shows the small current being taken to the relay AFTER the switch. MUST the layout ALWAYS be like this?

I have the current going from the A1 fused terminal to the relay first then onto the switched load.

badhuis · Joined: 20 Aug 2008 Posts: 1390 Location: Netherlands

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

As heavy current will only be pulled through the wires supplying the headlamps, will the two relays that cover the main and dip beam switch automatically protect the main switch?

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Here is another attempt at a diagram which aims to show how relays might fit into the re wire of my MG TC.

Please feel free to pick me up on errors etc.

DM · Joined: 21 Dec 2008 Posts: 212 Location: North Cornwall

Link across A1 and A2 on the regulator bypasses the accessory fuse.

Alternator output wants to go to the A terminal on the regulator, alternator wired as per your drawing means the ammeter will not read correctly.
Will only read the current drawn by the car without taking into account the charge current from the alternator.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

The instructions that come with the dynamater show it not connected to the regulator at all.?/Users/raywhite-newair/Desktop/http-::www.accuspark.co.uk:InstructionsPDF:Dynamator%20Positive%20Earth%20Instructions.pdf 2.webloc

Sorry, I can't seem to paste it like you did...

BTW I get the point about the A1 A2 fuse link error.

DM · Joined: 21 Dec 2008 Posts: 212 Location: North Cornwall

Your diagram has the alternator feed on the wrong side of the ammeter which will mean the ammeter will never show the charge current.

As long as the alternator output is connected to the A side of the ammeter the ammeter will read correctly.

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

One thing that confuses me about wiring the alternator is that the fitting instructions say take a 45 amp wire from it to the battery. I then have a heavy wire in the loom which according to the original wiring diagram (for a dynamo) should be connected from the starter switch to the 'B' side of the ammeter.

It has now been explained that the alternator needs to be connected to the 'A' side. This would mean that I will have wires from the - battery terminal to BOTH sides of the ammeter ...which I don't understand.???

ukdave2002 · Joined: 23 Nov 2007 Posts: 4104 Location: South Cheshire

Hi Ray as promised:

Whilst the RF 95 has fuses its less complicated no to use them, and you avoid have in circuits with 2 fuses.

Dave

Peter_L · Posted: Mon Feb 01, 2021 5:47 pm Post subject:

Excellent drawing Dave. Very Happy

Ray White · Joined: 02 Dec 2014 Posts: 6303 Location: Derby

Nice drawing, Dave. Thank you.

It looks like the small wire from the alternator eventually goes to the ammeter at A.

I will get it right eventually.