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Re: heater core

To: Hans Duinhoven <h.duinhoven@planet.nl>,
Subject: Re: heater core
From: Barney Gaylord <barneymg@MGAguru.com>
Date: Tue, 29 Apr 2003 17:19:09 -0500
At 10:00 PM 4/29/03 +0200, Hans Duinhoven wrote:
>.... Very much like my BGT - ('71 as well?).
>.... is there any regulator for the heater motor?
>Mine is on or off - iow silent or noisy...
>....
>----- Original Message -----
>From: "Barney Gaylord" <barneymg@MGAguru.com>
> > .... you can upgrade the heater core, the blower motor, and the 
> squirrel cage fan.  See here: http://chicagolandmgclub.com/photos/b_heater

Hey, I'm an MGA guy.  I only relate to MGB with it's similar to MGA.  I 
don't own any MG new enough to have multi-speed heater.  I helped rebuild 
the heater and took the pictures, but they wouldn't trust me inside such a 
new car, so I dunno what's behind the dash.

But I can tell you how to get a low speed for a heater motor that runs too 
fast.  The stock heater motor might draw about 4 amps, so figure it's 
around 3 ohms resistance when running.  The uprated motor might draw more 
like 6 amps, so figure about 2 ohms resistance when running.  You can wire 
a 1.6 ohm ignition ballast resistor in series with the heater power 
wire.  That would drop the stock motor supply voltage from 12 volts to 
about 7.8 volts, or the uprated motor from 12 volts to about 6.7 volts.  In 
either case they may have about the same mechanical power output and run 
about 2/3 of the speed of the stock motor.  That would reduce the air flow 
proportionately, and would also reduce the noise a LOT, like it may seem 
only half as loud.  Be aware that the ballast resistor would be cooking 
hot, almost the same as it is in the ignition circuit, so you need to mount 
it in a fire safe location.  Then to get the blower high speed back, all 
you need is a single pole single throw switch to bypass the ballast 
resistor, and you have a nice two speed heater.

Barney Gaylord
1958 MGA with an attitude
http://MGAguru.com

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