Thread: Auto Electrical Equivalent of Electric Busbar??

Without being able to inspect what you did, your wiring changes seem reasonable.

I wouldn't fit another earth link between the fuse block earth and the body/chassis because if the main body earth strap from the battery fails then all the current for the starter would pass though your new wire from the negative battery terminal to the fuse block which would cause that wire to burn-out and possibly start a fire.

When doing auto earthing....

IMHO and in a perfect world

on old school electrics there should be one earth cable going from the battery to the engine OR to a primary chassis earth (and then to the other), from that point all other earths should branch.

the issue you will have if you go for more of a networked pattern and you are relying on body earthing when a main earth cable fails then every secondary earth can potentially carry the full current of the starter or the alternator.

New school stuff follows a slightly different rule set because computers and charge monitoring systems.

Hello All,

Can a faulty 87A pin on a Bosch Five Pin Relay cause the relay to squeal? I can feel that the relay is opening and closing very fast and this is causing a vibration that in turn, emits a squeal. Take the connector to 87A off and silence rules.

Here is how I have wired the Low Beam circuit for the headlights.

Power to the lights is via the dash mounted off/on switch. The 2A has a floor mounted dipswitch.

Terminal 30 Power Input
Terminal 85 Ground
Terminal 86 Trigger from Dip Switch
Terminal 87 Output for Low Beam (Left)
Terminal 87A Output for Low Beam (Right)

For the High Beam I have a second five pin relay that is wired the same way - the only difference is that it picks up the high beams.

When I have swapped the relays around the circuit that squealed before is silent and the previously silent circuit is squealing.

================================================== =======================================

I also changed the wiring on the Five pin by just having an output off Pin 87 and linking it into the Low Beam Circuit. This means that Pin 87A is not used at all. Both headlights for low beam work

Same circuit for the high beam - output Pin 87 linked to common high beam and both lights work. No hook up to pin 87A and no squeal out of either relay.

Is it just a dicky relay?

================================================== ======================================

Did I mention that after turning on the dash lights switch I have never moved out of a vehicles seat and arrive at the front of a vehicle before!

I did not know whether I was somehow frying a gekko and it was in its death throws, or that I was about to see big clouds of smoke and sparks flying everywhere. It makes one hell of a loud squeal.

Kind regards
Lionel

youve made a self resetting relay.

the power is coming through the switched side of the relay to drive the signal side of the relay...

when the power comes on the relay tries to pull over, when the relay pulls over the power is cut (87a is NC to 30) so the relay relaxes, when the relay relaxes the contacts close the power comes on and when the power comes on.........

(add a small capacitor across the coil and you can make a pulse generator to fire an ignition coil)

what you have is a switching relay you would use it to alternate between a high and low beam

Changeover_relay.png

high beam on 87 low on 87A power through another relay or switch coming in on pin 30 to turn the lights on and off.


to achieve what I think you're trying to do you need a twin output relay (basically it has 2 pin 87 terminals usually 87 and 87b)

Relay_with_twin_output.png

Negative battery terminal would’ve at the same potential as the bonnet so the current flowing through the screw would be minimal.

Originally Posted by Blknight.aus

youve made a self resetting relay.

the power is coming through the switched side of the relay to drive the signal side of the relay...

when the power comes on the relay tries to pull over, when the relay pulls over the power is cut (87a is NC to 30) so the relay relaxes, when the relay relaxes the contacts close the power comes on and when the power comes on.........

(add a small capacitor across the coil and you can make a pulse generator to fire an ignition coil)

Hello Dave,

So I go back to the 87 output that taps into a common wire to the low beam for one relay

The second relay is for high beam circuit.

I got both examples of wiring off the internet specifically for Bosch style 5 pins plugs. Each circuit appeared on different author's pages.

I thought one circuit cuts into the pre-existing dicky system: the no 87a pin circuit

While the using 87 to power the left light and 87A to power the right light meant I could use brand new wires that did not have any joints in it. All done independent of the old wiring.



Kind regards
Lionel

Originally Posted by Lionelgee

Hello Dave,

So I go back to the 87 output that taps into a common wire to the low beam for one relay

The second relay is for high beam circuit.

I got both examples of wiring off the internet specifically for Bosch style 5 pins plugs. Each circuit appeared on different author's pages.

I thought one circuit cuts into the pre-existing dicky system: the no 87a pin circuit

While the using 87 to power the left light and 87A to power the right light meant I could use brand new wires that did not have any joints in it. All done independent of the old wiring.



Kind regards
Lionel

from your description, you've pinned up for having twin out puts (one for left one for right) and are just trying to turn on the relay to turn on both left and right filiments of high or low beam with one relay.

that will work fine with a change over relay untill you get a bad earth and then the relay becomes self energising (or de energising depending on which way and where the earth failed)

bet if you tied both the wires for each sides relevant filament to a single pin 87 on each relay while powering up from 30, earthing to a solid earth (not your fuse block termnial) that is carrying potential from both the headlight and the battery) from pin 85 (signal power comes in on 86, double check this its been a while but its only relevant if you're using relays with blocking diodes, bleeds, internal voltage sensing or internal LED indicators) to the battery(ies) (and no Im not going into the specifics of current flow versus voltage potential here, just make sure all the earths are good and tied together)

oh and check my first post for the edit.

Originally Posted by workingonit

Battery terminal too close to but not quite touching steel bonnet, enough to start a welding arc and when enough metal migrated welded the bonnet to the metal battery terminal bolt. Flat battery and bonnet that wouldn't open without a lot of force. Diesel engine...petrol engine with fumes might have meant a vehicle fire.

Dreaming