Date:         Mon, 2 Apr 2007 01:55:45 -0400
Reply-To:     Jonathan Farrugia <jfarrugi@UMICH.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Jonathan Farrugia <jfarrugi@UMICH.EDU>
Subject:      Re: Attn: Electrical Gurus! (I searched archives)
In-Reply-To:  <461089DE.4040100@earthlink.net>
Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed

this blower motor overdraw is a problem for all the 80's vw's i have
owned.  to degree i believe it has to do with IEC design standards as
opposed to those of say NEMA.

IEC
http://en.wikipedia.org/wiki/International_Electrotechnical_Commission

NEMA
http://en.wikipedia.org/wiki/National_Electrical_Manufacturers_Association

basically i generally equate IEC with european electrical design.  in this
age of price point comparision and quick obsolescence IEC has for the most
part become the 'world' standard in electrical gear and design.  IEC
components/design is great if you never ask anything of your equipment
above what the user manual lays forth and if in addition to that you
practice real preventative maintenance.

i say that to say that IEC is engineered to function to the specification
but has little if no capacity beyond that.  so little extra capacity that
if anything else on the machine goes out of spec the IEC components tend
to live a drastically shorted life cycle.  in the field i have rarely
replaced NEMA gear due to failure.  on the other hand IEC equipment
failure becomes a regular part of maintenance on heavily used or older
equipment.

often if space allows on the machine, IEC equipment will be replaced with
NEMA gear after multiple failures.  the other hack is if space allows or
you are doing the original engineering is to up size the IEC equipment the
next size up so that it provides some extra capacity and thus lives longer
in its application.

this is exactly what happens with the vw blower fan system and why the
'solution' involves upgrading the original electrical design.  on the
rabbits, jettas, sciroccos.  they used round pins (european models) in
large plastic connectors to plug into the back of the fuse box.  the pin
associated with the blower motor over time melts the connector and the
back of the fuse box but generally doesn't pop the fuse until it is in the
last stages of failure.

what is happening is that the system/circuit that operates the blower
motor was designed just to capacity.  thats okay to get by for the first
4 years of the vehicles life but after that the system starts to move out
of spec and the components cannot handle the additional load.  that is
the blower motor bearings loose efficiency, and the wiring due to the
high heat cycles from 'undersized' wire and connections increases in
resistance.

so the solution is to either rebuild the entire system to bring it back to
stock specs, which is costly if the parts can still be had in some cases,
or to up size certain parts of the system for the extra demand on system.

i've yet to carry this out on my van although it needs it but, i've done
it on several A1's.  my hack has involved using the normal power to the
fan switch to act as the control circuit on one of the larger standard
bosch relays, when the fan switch is in the high position.  to provide
power to the relay i tapped off one of the available pins (1/4" spade) on
the back of the fuse box with either an inline fuse of a fuseable link.
this powers the relay and depending on how thorough you want to be or how
badly your system has suffered you can run a new wire from the relay
output to the fan for the high speed.

none of this of course is going to fix those worn out bearings in your fan
motor.

jonathan

On Sun, 1 Apr 2007, Mark Drillock wrote:

> Yes, of course the terms were used a little loosely. I know the
> difference between volts, amps, watts, ohms, farads etc. The point is
> that full power only goes through the high position of the switch and
> the high position would be the one that could benefit from a relay if
> any could.
>
> Mark
>
> Alistair Bell wrote:
>
>> Hi,
>>
>> my understanding is that the switch handles "full" voltage in all the
>> on positions. I am sure Neil will chime in here, but the switch
>> "merely" directs the power to 2 wire wound resistors, speeds 1 and 2,
>> and directly to motor on speed 3.
>>
>> So it is handling full voltage. Maybe you mean currrent?
>>
>> Alistair
>>
>>
>> '82 westy, diesel converted to gas in '94
>> http://www.members.shaw.ca/albell/
>>
>> On 1-Apr-07, at 3:56 PM, Mark Drillock wrote:
>>
>> You are correct sir.
>>
>> Mark
>>
>> Karl Wolz wrote:
>>
>>> You only need the relay for the highest speed setting, since that
>>> is the
>>> only one that uses full voltage through the switch, or so I've been
>>> told.
>>>
>>> Karl Wolz
>>>
>>> -----Original Message-----
>>> From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On
>>> Behalf Of
>>> neil
>>> Sent: Friday, March 30, 2007 6:38 PM
>>> To: vanagon@GERRY.VANAGON.COM
>>> Subject: Re: Attn: Electrical Gurus! (I searched archives)
>>>
>>> Hi Matt.
>>>
>>> Thanks for all that info.
>>>
>>> I'm always impressed with how much the list knows and contributes!
>>>
>>> I had heard of someone thinking of using a relay in the circuit a la
>>> the headlight upgrade. But as you said it then becomes one relay per
>>> speed. Kinda what I thought would happen.
>>>
>>> I decided to go with stock. (See previous posts) In fact I just got
>>> back from parts place with new switch. Picked up new wiper shaft
>>> assembly, but am still waiting on bushings for brake pedal.
>>>
>>> ................
>>
>>
>
>
>