Subject: Re: [Healeys] Another con - fused question

From: Richard Ewald <[email-masked]>
Date: Tue, 1 Jan 2013 11:03:58 -0800

Only items downstream from the fuse will be protected by that fuse.  So if
you put the fuse downstream of the relay, the relay won't be covered.  If
you put it upstream on the relay the relay will be protected.

On Tue, Jan 1, 2013 at 11:01 AM, john spaur <[email-masked]> wrote:

> There are two white wires going to the OD relay. One comes from the fuse
> block at A3.
>
> The other goes from the relay down to the overdrive switch on the dash. Is
> this the correct wire to fuse?
>
> TIA
> John Spaur
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From: john spaur <[email-masked]> mail.com>
Date: Tue, 01 Jan 2013 12:34:50 -0800

If I understand you correctly the fuse needs to be placed between 
terminal A3 (which is one side of an existing fuse) and C1 on the 
overdrive relay. Correct?

David Nock stated the white wire needs to be protected but I think he 
may have meant the white with green wire coming off for terminal C2 
on the OD relay because the relay should be protected at A3 on the fuse block.

John

At 11:03 AM 1/1/2013 -0800, Richard Ewald wrote:
>Only items downstream from the fuse will be protected by that 
>fuse.  So if you put the fuse downstream of the relay, the relay 
>won't be covered.  If you put it upstream on the relay the relay 
>will be protected.

[email-masked]

---

From: Bob <[email-masked]>
Date: Tue, 01 Jan 2013 16:07:30 -0500

Conceptually this concept is flawed.   The fuse does not protect anything 
downstream of the
fuse except the wire!   If he fuse blows it does so because the device, the 
relay in this case,
has already failed or there is a wire short.  The fuse is sized to allow normal 
working with the
device or devices downstream.

To look at it another way...  In the Kitchen one tries to run the toaster, 
microwave, and the
coffee maker at the same time.  The fuse/breaker trips not because it protected 
any device but
it protected the wire from overload and the potential of an overheated wire from 
stating a fire.

That is the fuse function, to protect you and the wire, not the device....

Bob
55BN1

[email-masked]

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From: [email-masked]
Date: Tue, 1 Jan 2013 17:02:01 -0500 (EST)

I agree with the below & would add that I would put the fuse in the line
leading from the relay to the solenoid. This assumes your wiring harness is in
good overall condition. It is the solenoid that draws a high current during
the initial engagement of the OD & can continue to draw high current if it
does not engage the holding coil circuit due to maladjustment of the OD
solenoid linkage. This could either melt the wire or fry the OD solenoid &
either condition is what I want to prevent with the fuse. My harness is new &
I am not particularly concerned about shorts in the wiring.
Gary Hodson

-----Original Message-----
From: Bob <[email-masked]>
To: Richard Ewald [email-masked]
Conceptually this concept is flawed.   The fuse does not protect anything
downstream of the
fuse except the wire!   If he fuse blows it does so because the device, the
relay in this case,
has already failed or there is a wire short.  The fuse is sized to allow
normal
working with the
device or devices downstream.

To look at it another way...  In the Kitchen one tries to run the toaster,
microwave, and the
coffee maker at the same time.  The fuse/breaker trips not because it
protected
any device but
it protected the wire from overload and the potential of an overheated wire
from

stating a fire.

Bob

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From: Richard Ewald <[email-masked]>
Date: Wed, 2 Jan 2013 11:56:44 -0800

You and Robert are both wrong.
Picture the two following circuits
Batt---------switch----------X--fuse----light bulb--gnd
wire rubs to ground at point X. The switch and wiring upstream of the
failure will burn out due to the excess current running through it.  it is
not protected by the fuse.
Now look at this circuit
Batt---fuse----switch---X----light bulb---gnd.
failure is in the same place, point X.  Only this time the switch and the
wiring is protected by the fuse blowing before the switch is damaged.  The
switch and wiring is protected by the fuse.
I stand by my comments.

On Tue, Jan 1, 2013 at 1:07 PM, Bob <[email-masked]> wrote:

> fuse except the wire!

[email-masked]

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From: Greg Wilkinson <[email-masked]>
Date: Tue, 01 Jan 2013 13:04:29 -0800

A3 offers no fuse protection. The fuel pump and OD white wires are on 
the same side as the ignition power lead. Only wires on the other side 
of the fuse (green wires) will be protected.
> may have meant the white with green wire coming off for terminal C2 on 
> the OD relay because the relay should be protected at A3 on the fuse 
> block.
>
> John

[email-masked]

---

From: "BJ8 Healeys" <[email-masked]>
Date: Tue, 1 Jan 2013 15:18:10 -0500

It depends on what you want to protect with the fuse, John.  
The white wire that goes to the dash switch is a part of the circuit that
activates the relay coil via the white/purple wire to relay terminal W2.
If you put a fuse in the white wire, you are protecting the wiring from a
short in the relay coil.  
If you want to protect the wiring in case of the overdrive solenoid burning
up, you should put the fuse between relay terminal C2 and the white/green
wire that goes to the overdrive.
I made up a wire with an in-line 20A fuse to connect to relay terminal C2 on
one end and to the white/green wires normally connected to C2 at the other
end (I prefer "adapter" wires to cutting into the original wiring).
A few years ago, I actually had a solenoid melt-down before I installed the
fuse.  It didn't damage the wiring, but seeing what it did to the solenoid
rubber cap, I feel better about having the fuse there.

Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC  USA

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of john spaur
Sent: Tuesday, January 01, 2013 2:01 PM
To: [email-masked]
Subject: [Healeys] Another con - fused question

TIA
John Spaur

[email-masked]

---

From: Alan Seigrist <[email-masked]>
Date: Thu, 3 Jan 2013 08:04:51 +0800

Greg is correct here.  On any white wire on any british car (including all
austin healeys), it is switched power, unfused.

http://www.kabel-schmidt.ch/PDF/lucas.pdf

Note what this says about white color on the second page.

I don't know which car you have, but "terminal A3" could very well be
simply a junction block, not a fuse block.

You can put a fuse on the white wire between the junction and the solenoid.

Alan

On Wed, Jan 2, 2013 at 5:04 AM, Greg Wilkinson <[email-masked]
> wrote:

> A3 offers no fuse protection. The fuel pump and OD white wires are on the
> same side as the ignition power lead. Only wires on the other side of the
> fuse (green wires) will be protected.
>
>
>> David Nock stated the white wire needs to be protected but I think he may
>> have meant the white with green wire coming off for terminal C2 on the OD
>> relay because the relay should be protected at A3 on the fuse block.
>>
>> John

[email-masked]

---

From: Alan Seigrist <[email-masked]>
Date: Thu, 3 Jan 2013 08:05:30 +0800

sorry I mean the last page.

On Thu, Jan 3, 2013 at 8:04 AM, Alan Seigrist <[email-masked]> wrote:

> On Wed, Jan 2, 2013 at 5:04 AM, Greg Wilkinson <
> [email-masked]> wrote:
>

[email-masked]

---

From: "BJ8 Healeys" <[email-masked]>
Date: Thu, 3 Jan 2013 09:53:51 -0500

What raised this discussion in the first place was fusing the overdrive
circuit.  The O/D solenoid has a pull-in coil that draws high current and a
holding coil that draws less current.  The solenoids can fail in such a way
that the internal switch from the pull-in coil to the holding coil does not
work, leaving the pull-in coil continuously activated and drawing high
current.  The concern is that the high current can damage the wiring to the
O/D.  I had such a failure once that burned up the solenoid but it did not
damage the wiring, fortunately.  But the possibility that it could have
convinced me to put a fuse in the circuit.  The ultimate purpose of a fuse
is to protect the wiring, because it's much easier to replaced a failed
component than melted wire in the harness.

You can put a fuse in the white wire, but the white wire is a heavier gauge
than the wire to the O/D solenoid.  I preferred to put the fuse in the
white/green wire to the gearshift switch and solenoid so that the smaller
gauge wire is protected.  Plus, if the fuse blows, I can be pretty sure the
problem is either in the O/D wire or the solenoid.  A blown fuse in the
white wire leaves several other possibilities to have to investigate (relay,
throttle switch, dash switch and wiring to them).'

Steve Byers
HBJ8L/36666
BJ8 Registry
Havelock, NC  USA

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]
On Behalf Of Alan Seigrist
Sent: Wednesday, January 02, 2013 7:05 PM
To: [email-masked]
Cc: Healey List
Subject: Re: [Healeys] Another con - fused question

Alan

[email-masked]

---

From: Bob <[email-masked]>
Date: Fri, 11 Jan 2013 18:50:29 -0500

[email-masked]

---

From: Richard Ewald <[email-masked]>
Date: Fri, 11 Jan 2013 16:05:34 -0800

Sorry but  you said
>>The fuse does not protect anything downstream of the
fuse except the wire!
This is incorrect as I showed in my diagram, when correctly placed this is
an incorrect statement.  Any and all components downstream from the fuse
are protected.  If we take your statement and change the word from wire to
component(s) it would be a correct statement.

But what the hell do I know, I just taught this stuff for about 20 years
and edited the electrical fault tracing course manual for a major car
company.
:::shrug:::

On Fri, Jan 11, 2013 at 3:50 PM, Bob <[email-masked]> wrote:

>  Hi Richard,
>
>                  Been away from this for a few days.
>
>                  I will stand by my comments too.
>
>                  The fact that the fuse blows is indicative of an overload
> condition.  It acts as a safety to prevent damage to the wire or wiring.
> You are correct in your example that the switch may be protected.  However
> that is incidental to the fuse's primary function.   Best practices place
> the fuse as close to the current source as possible.  All is subject to
> Kirchoff's 1st or current law.
>
> Bob
> 55BN1
>
>
> On 1/2/2013 2:56 PM, Richard Ewald wrote:
>

[email-masked]