Picked this up at Harbor Freight
http://www.harborfreight.com/20-amp-automotive-fuse-circuit-tester-67725.html
I have found it to be helpful working on this kind of problem.
Ken

On Thu, November 3, 2011 1:12 am, Alistair Bell wrote:
> yes, and key on power to "15" on coil is supplied by the notorious D15
> (clear on wiring diagrams for vin G 055 690 and up, less clear on the
> earlier '86). The heater is an added load on D15.
>
> alistair
>
>
> On 2011-11-02, at 9:57 PM, Scott Daniel - Turbovans wrote:
>
>> The breather heaters I have seen were 'stand alone' .......in other
>> words, just added on.
>> They're connected to the black '15' wire going to the coil I believe.
>> they can be retrofitted to any waterboxer engine easily.
>>
>> thanks for your diligent work here and posting of pictures.
>>
>> Scott
>
>