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Manifold heater on hs2 carb on 948 engine

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0123 Mike D
Biddulp, Staffs, UK   GBR
18 gauge wire is rated to 10 amps Jim sad smiley

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0123 Mike D
Biddulp, Staffs, UK   GBR
Thanks John smiling smiley

Please will you clarify,
you say your manifold heater
ran your battery flat after the
thermostatic switch failed on.

Was your heater wired direct from
the battery or wired through the ignition?

In reply to # 26447 by John in Eugene I believe that is the maker of the thermostatic switch that controls the induction heater (the black domed cylinder device). At least a similar switch is used to control the AED on my Jaguar saloon.

John F. Quilter
Eugene, Oregon USA

In reply to # 26444 by 0123 What did your "Otter" switch do please John?

0123 Mike D
Biddulp, Staffs, UK   GBR
In reply to # 26449 by usmh3 There should also be a wire direct from the terminal on the dashpot heater to that little clamp that is screwed against the bulbous side of the Otter switch. That is where it gets power supplied from.

No details here of the power rating, presumably because the UK never really needed such heaters????
I could have done with one in 62/63 Rob


I wonder if there was always power from the coil to the Otter switch and the heat only came on when the switch cooled down enough to trigger??? Green wire to the switch or is it white, John? Looks green from my PC.



Edited 1 time(s). Last edit at 2017-10-08 01:37 AM by 0123.

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0123 Mike D
Biddulp, Staffs, UK   GBR
Are you likely to use your heater John?

John in Eugene Avatar
John in Eugene Gold Member John Quilter
Eugene, Oregon, USA   USA
I'm sure it was fed through the ignition but apparently the draw could overwhelm the generator if on continuously which it was not intended to be.

John F. Quilter

In reply to # 26452 by 0123 Thanks John smiling smiley

Please will you clarify,
you say your manifold heater
ran your battery flat after the
thermostatic switch failed on.

Was your heater wired direct from
the battery or wired through the ignition?

In reply to # 26447 by John in Eugene I believe that is the maker of the thermostatic switch that controls the induction heater (the black domed cylinder device). At least a similar switch is used to control the AED on my Jaguar saloon.

John F. Quilter
Eugene, Oregon USA

In reply to # 26444 by 0123 What did your "Otter" switch do please John?

John in Eugene Avatar
John in Eugene Gold Member John Quilter
Eugene, Oregon, USA   USA
I think it is green and on a Minor (1960) comes via the windscreen wiper motor. Now, who knows what the band around the carb dashpot is for? Another heating element?

John F. Quilter

In reply to # 26454 by 0123
In reply to # 26449 by usmh3 There should also be a wire direct from the terminal on the dashpot heater to that little clamp that is screwed against the bulbous side of the Otter switch. That is where it gets power supplied from.

No details here of the power rating, presumably because the UK never really needed such heaters????
I could have done with one in 72/73 Rob


I wonder if there was always power from the coil to the Otter switch and the heat only came on when the switch cooled down enough to trigger??? Green wire to the switch or is it white, John? Looks green from my PC.

tjt77 timothy Trevithick
Grass Valley, California, USA   USA
These are common on N American import versions.. its MIGHT possibly be of use in sub zero temperatures where carb icing is an issue (Canada's northern territories) .. in normal climates (up to 2 -3o below freezing) its not needed however.. Ive got a few of these in my parts stash removed from various minors over the years.. the Marina's had them too.. as do the 'austin america' (1100/1300 fwd cars) and minis.. my advice is remove it and go with the 'normal' distance piece....

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emjay Jim English
Marietta, PA, USA   USA
Being a green wire it is on the fused side of the ignition with it's 35 amp British rated fuse, which is about 17 amp usage. That circuit has the fuel pump, turn signals, brake lights, heater, wipers. (did I forget any?) On a rainy cool night you probably will be using all of these including the heater and typically the fuse will not blow. Now the dynamo will not be able to keep up, but the fuse will be good, so the load of the heater can not be excessive. The dashpot header tends to show up on later models and continued on the Mini and ADO16 variants. The power for this heat comes from the terminal clamped on the outside of cover for the thermostat putting the two heaters in parallel. You can use the wire from the wiper motor (the solid green) but originally it came from the fuel gauge as I recall.

0123 Mike D
Biddulp, Staffs, UK   GBR
Am I correct please John,
your manifold heater was wired
through the ignition yet it still
flattened your your battery even
though the engine was running?


In reply to # 26457 by John in Eugene I'm sure it was fed through the ignition but apparently the draw could overwhelm the generator if on continuously which it was not intended to be.

John F. Quilter

In reply to # 26452 by 0123 Thanks John smiling smiley

Please will you clarify,
you say your manifold heater
ran your battery flat after the
thermostatic switch failed on.

Was your heater wired direct from
the battery or wired through the ignition?

In reply to # 26447 by John in Eugene I believe that is the maker of the thermostatic switch that controls the induction heater (the black domed cylinder device). At least a similar switch is used to control the AED on my Jaguar saloon.

John F. Quilter
Eugene, Oregon USA

In reply to # 26444 by 0123 What did your "Otter" switch do please John?

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0123 Mike D
Biddulp, Staffs, UK   GBR
Do you cold climate chaps
twist your air intake round so
it picks up near the manifold?

In reply to # 26459 by tjt77 These are common on N American import versions.. its MIGHT possibly be of use in sub zero temperatures where carb icing is an issue (Canada's northern territories) .. in normal climates (up to 2 -3o below freezing) its not needed however.. Ive got a few of these in my parts stash removed from various minors over the years.. the Marina's had them too.. as do the 'austin america' (1100/1300 fwd cars) and minis.. my advice is remove it and go with the 'normal' distance piece....

0123 Mike D
Biddulp, Staffs, UK   GBR
In reply to # 26460 by emjay Being a green wire it is on the fused side of the ignition with it's 35 amp British rated fuse, which is about 17 amp usage. That circuit has the fuel pump, turn signals, brake lights, heater, wipers. (did I forget any? Coil) On a rainy cool night you probably will be using all of these including the heater and typically the fuse will not blow. Now the dynamo will not be able to keep up, but the fuse will be good, so the load of the heater can not be excessive
How about someone measuring the
current manifold heaters take please?
.
The dashpot header tends to show up on later models and continued on the Mini and ADO16 variants. The power for this heat comes from the terminal clamped on the outside of cover for the thermostat putting the two heaters in parallel. You can use the wire from the wiper motor (the solid green) but originally it came from the fuel gauge as I recall.

emjay Jim English
Marietta, PA, USA   USA
It was recommended to rotate the intake on the dry element air cleaner for the 948 clockwise as far as it would go, which was no more that 20-30°. They must have thought the air was significantly warm over there. I do it once in a while, but more as a gimmick then thinking it makes a difference. On the other hand the later FWD cars had a short curved intake that was to be inserted into a shroud around the exhaust manifold. That could make a difference. Marinas had the connection controlled by a bi-metallic flapper.

John, Mike has a point there. When your car was at rest, the circuit should have been turned off, so even if the thermostat failed closed, your battery would not have gone flat in the garage. Or was the draw so significant that the battery went flat while driving with other accessories in use? Please confirm the details of the occurrence.

emjay Jim English
Marietta, PA, USA   USA
The coil is a white wire, which is un-fused. It does of course consume the available amps out of the dynamo.

0123 Mike D
Biddulp, Staffs, UK   GBR
The very smartest way
to connect current soaks
like the manifold heater,
the interior heater is via
a voltage sensing relay.
Only works with alternators.

The next smartest is via
a normal relay pulled in
by a connection to the
output post on the dynamo.
Only works with dynamos

The third smartest method
is via a normal rely pulled
in by the ignition circuit.
Works with either.

The power wire to the relay
should come from the battery.
It must be fused.

John in Eugene Avatar
John in Eugene Gold Member John Quilter
Eugene, Oregon, USA   USA
Yes. That was a standard feature of the air cleaner intake on the America but not on any Minors I've seen.

John F. Quilter
Eugene, Oregon USA

In reply to # 26463 by 0123 Do you cold climate chaps
twist your air intake round so
it picks up near the manifold?

In reply to # 26459 by tjt77 These are common on N American import versions.. its MIGHT possibly be of use in sub zero temperatures where carb icing is an issue (Canada's northern territories) .. in normal climates (up to 2 -3o below freezing) its not needed however.. Ive got a few of these in my parts stash removed from various minors over the years.. the Marina's had them too.. as do the 'austin america' (1100/1300 fwd cars) and minis.. my advice is remove it and go with the 'normal' distance piece....

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