1976 T3 Starter Motor wiring problem.

[Geoff]

1976 T3 Starter Motor wiring problem.
This is the problem they all get - where the relay under the right side panel clicks but the current supplied to the starter motor is not enough to energise the “big solenoid” that sits on top of the starter motor and throws in the heavy duty power and moves the gear. I now suffer this 50% of the time.
The published solution is to beef up the power supply to the relay behind the right side panel.
I am pretty sure I do suffer the inadequate power problem as the starter motor spins fine and the bike starts if I bridge the heave duty battery supply lead on the starter motor to the small spade connector on the “big solenoid”

I wanted to avoid doing the standard fix as the relay is inaccessible behind the brake master cylinder, the linked brakes can be tough to get working again if I disturb the master cylinder, and the 34 year old wiring is prone to develop fresh faults if it is disturbed too much.

So I set about a short cut solution. I decided to power the “big solenoid” with a cable direct from the positive battery terminal, switched through a new micro relay that I intended to site behind the left side panel.
And the plan was to energise the new micro relay by connecting the cable with the inadequate current from the existing relay under the right hand panel to one of the low power input terminals, and connecting the other low power cable to the battery earth side.
So I set up the relay cables
One high power with a banjo connector for the battery positive terminal. Other high power with a female spade connector for the “big solenoid”.
One low power with a male spade connector to receive the female spade connector on the existing 34 year old wire transferred from the “big solenoid” Other low power terminal on the new micro relay fitted with a banjo connector to batter earth (negative) terminal.

I tested the micro relay wiring and operation by using it to light a test bulb that I placed in series on the high power switched circuit of the relay. The light went on and off with a nice sounding click when I connected the low power leads to the battery, one lead to Postve, one to negtve. All was fine.

So then I connected up the new extra relay for real.
Turned on the ignition
Pressed the starter.
Click from the old relay, nothing else happened
Tried again
Click from old relay.
Fuse that protects old relay blows (15A Fuse)
I am pretty sure I connected it up same as I did when I did the test with the bulb. The connectors on my relay wires are all different depending upon their purpose, so it would be tough to get it wrong.


Anyone got any ideas why my alternative fix will not work?

Thanks
Geoff

 

[john zibell]

Geoff,

Just replace the funky starter relay with a standard 30 amp automotive relay. You don't have to remove the MC to remove the old relay. You will also find the numbers on the Marelli relay and on the standard 30 amp relay are the same. Just follow the numbers. http://shop.advanceautoparts.com/webapp ... AMPAMS____

 

[Geoff]

Thanks John
But this is not really the issue.
The original relay works fine
What is lacking is the power supply to the starter "big solenoid"
And my solution to fit a direct cable powered by a new relay caused a fuse to blow

Any ideas why my modification would not work?

Geoff

 

[Brian UK]

From what you describe, I don't see why it does this. All I can think is that you have made a small error somewhere. Are you sure you got the right terminals on the micro relay?
Other than that, when you re-routed the wire from the original relay (which went to the solenoid) maybe it was damaged, and is earthing out, or broke?

 

[john zibell]

Thanks John
But this is not really the issue.
The original relay works fine
What is lacking is the power supply to the starter "big solenoid"
And my solution to fit a direct cable powered by a new relay caused a fuse to blow

Any ideas why my modification would not work?

Geoff

The contacts in those old relays aren't great. Also they are not tightly sealed. After a couple of decades, they don't work so good even if in energizes. Try the relay, easiest solution. Besides, I've seen this before and the new relay cured the problem.

 

[Brian UK]

Equally, my V50 has the old type relay and had the same problem. I changed the wiring with a new supply direct from the battery, and cured the problemm. The old relay is still there.
Did the same mod on the SPIII when it became uncertain whether the starter motor would go or not. Again still the same relay.
Also cured a Cali 1100i in the same way, though that was more difficult due to the interaction between the relays.
I agree that relay contacts don't improve with age, but the real problem is the fact that the supply to the solenoid goes up and down the bike a couple of times, via the ignition switch and fuse, and many connectors, with wire that was barely up to the requirement in the first place.

 

[Geoff]

New fuses arrived in post yesterday. Blown two more already.
I retested my wiring using a test bulb with everything connected direct to the battery. My relay wiring works fine.

Tried to light my test bulb by using the starter motor "Big Solenoid" lead from the spade connector. Kept all wires well clear of both each other and the bike. Definitely no opportunity for shorts (had got to the point that I was convinced that shorts were the answer. Starter fuse blows again

Fitted new fuse.
Noticed that new micro relay has a diode fitted and that two of the terminals are marke as positive.
Switched around wiring to recognise polarity
Re-tested the micro relay as now wired with direct connections to battery. Bulb lights fine.

Switched wires to give feed from wire taken from solenoid
Fuse blows......

I am now contemplating a simple answer
Maybe the power draw of the diode fitted micro relay is simply too high for the circuit??
Buying new bog standard non diode 4 pin relay today and will try again

Let you all know of progress

Geoff

 

[Brian UK]

I think I got a bit lost in there.
Are you saying that with your new relay correctly wired (accounting for the diode) but the solenoid not actually connected to it, the fuse blows?
Because that would not be possible unless there is a short somewhere.
BUT, if you are saying that with the new relay correctly wired (etc. etc.) and the solenoid connected, when you press the start button the fuse blows, then that could be a faulty solenoid. But it could also be the fuse is a little on the small size for the current now flowing through the solenoid (now that it's getting the full 12 volts).

 

[Geoff]

I am saying that with the new micro relay correctly wired I can make the relay light a test bulb if i make direct connections to the battery.

But if I use the wire removed from the spade connector on the solenoid to put the positive current into the new micro relay low power circuit. Then the relay is only powered when I press the starter button. And when I press the starter button the original starter fuse blows even with only the test bulb in the circuit. So the fuse blows with a trest bulb in the circuit. I have not tried to use the new set up to put power into the solenoid. So the possibility of a fault in the solenoid does not arise.

I will try again with a more simple relay (no diode)

And I am tempted to replace the old starter relay that fits under the right hand side panel, to see if that helps

Geoff

 

[Geoff]

Thanks to all of you for your thoughts and ideas.
Today I bought a basic 4 post relay. I was going to use it either as a substitute for the Micro relay with the diode that I had been using in my custom solution, or to use it to replace the original relay that sits under the right hand panel behind the brake master cylinder.

I started by looking at the original relay. That thing must have its origins in a 1930’s Milan telephone exchange! It is large and made from semi opaque plastic through which a neat little copper coil is visible. The whole thing is clamped to the frame. This is not a relay socket that will receive a plug in replacement. So my idea of plugging in a replacement became more complicated.

So I decided to have a go at the more normal starter relay solution - beefing up the power supply. So I disconnected the brown wire that bridges two terminals, and replaced the connection to the second terminal with a new wire direct to the battery. It works. Over the next few days I will discover if it is a cure.

Will let you know

I still cannot figure out why my original plan to fit a tandem relay to switch power direct from the battery to the spade terminal on the solenoid will not work. I felt that was a rather elegant solution. Full power to the spade terminal coupled with minimal disturbance to existing wiring.

Geoff

 

[john zibell]

Geoff,

Go back and look at my post. The spade terminals on the old relay, have the same numbers as the new relay. Just transfer them one at a time.

 

[Brian UK]

I trust you have put the new feed to terminal 30. This should be a permanent cure, but for peace of mind, changing the relay is easy, as John says, the numbers on the terminals are conveniently the same.

 

[Geoff]

John, Brian
OK
You have shamed me into it
I will replace the existing relay as well

Geoff

 

[john zibell]

John, Brian
OK
You have shamed me into it
I will replace the existing relay as well

Geoff

Geoff,

Take a close look at Brian's post above. Using a new supply line (12 V) on terminal 30 is a good idea. Be sure to insulate the old spade connector well (tape it up) so it cannot short to ground.

 

[Brian UK]

Ideally, you should add a 15A fuse to that new wire.

 

[Geoff]

OK, I have now done the complete job.
In my original plan you will recall that I blew a fuse every time when I used the existing red wire to the solenoid spade terminal to trigger a new micro relay that takes full battery power direct to the starter solenoid.

Now I have discarded the old Marelli relay that sat under the right hand panel.
And replaced it with the same micro relay that blew a fuse every time I used it as planned above

The replacement micro relay has a direct feed from the battery to tml 30

Everything now works perfectly.

I will add a fuse in line on the terminal 30 lead

I still cannot figure out why the original fix would not work

Thanks for all or your help

Geoff