I started this as a reply to an Auxiliary Water Pump Question and it
Morphed into an Un-Solicited Rant.

[Auxiliary Water Pump's Purpose:

'Burn out it's bearings and/or wear out it's brushes to be able to Pull more
Amps and burn out the CCU (Climate Control Unit) so the dealer can sell you
both!

UNLESS, You're savvy enough to install a 1 Amp inline fuse on the Aux pump's
Positive lead.(As close as possible to the Power Source.) ]

1 amp ATO/ATC fuse (BLADE TYPE)
Blue Sea Systems (In A "Package" of Two each.)
"Tin Plated Non-Corrosive Blades"
Blue Seas Part Number 5235
From West Marine (They'll probably have to Special Order them...3-4 days)
[Sorry I didn't save the receipt,So I don't have the WM part #]
(2) packs of fuses was about $5.00 USD

Inline type ATO/ATC fuse holder (Black Rubber with W.T. Cap)
ANCOR brand part # 607022
From the "soon-to-no-longer-be-in-business" Boater'sWorld
Two fuse holders $4.66 plus Taxation
[Whoa, these came from MARINCO their number 100208
(707) 226-9600 WWW.MARINCO.COM ]

Radio Shack part numbers for:

Inline Fuse Holder #270-1281 [$2.69 USD + Taxation]
(For Glass Buss type 1-1/4 X 1/4 ",rated 250VAC,10A fuses)

1/4 Amp,250 volt fuse #270-1002 (Pkg of Four) [$1.99USD + Taxation]

1 Amp,250 volt Fuse # 270-1005 (Pkg of Four)[$1.99USD + Taxation]

For connectors,
I really like ANCOR brand Heat Shrink,Adhesive Lined,Butt Connectors
(of the appropriate AWG gauge). 'Once your connectors have cooled,
a nice coating of Starbrite's Liquid Electrical Tape on the ends
(At the wires) provides An Obsessive's final Corrosion Protection.

1.I'm gonna start with an inline 1/4 Amp fuse for the Cabin Air Temp Sensor Fan.
('Cannot seem to find anything smaller ,Yet!)
2.1 Amp inline fuse on the positive side of the Auxiliary Water Pump.
(As close to the Power source as possible)(I'm gonna try a 3/4 amp inline first)
3.The Chassis was fitted with one of the Exterior (Of the Fuse-box) 30 Aluminum Strip Fuse holder for the Cabin Blower Fan.
[Anybody know if these fuses are Fast or Slow-Blow?]
(I think I'm gonna retrofit an ATO/ATC type fuse holder and go with a 25Amp fuse.)
(A healthy Blower Fan [Good Bearings and Brushes should draw less than 25 Amps.] )

The Auxiliary Electric Radiator Fans Relays, are another area of concern.
Even with the Aux Fans Resistor (Behind the LF headlight assembly)

The new K9 relay MB # 001 542 96 19 (Made in Hungary no Less!); I got
to replace the old one came with a Green 30 Amp ATO/ATC fuse installed.
In Reading K6JRF's "Page" http://www.k6jrf.com/MB_CTS.html
I note the Aux fans on HIGH will draw about 23 Amps.
So, I'm gonna swap the 30 Amp out for A 25 Amp.

The relay K10's High Power side is powered by fuse D in the fuse box
(16 Amps) AND K6JRF pegs Low fan operation @ 12.4 Amps...
Not much I can do there (Unless I can find a 13 Amp fuse to put inline
between Fuse D and K10...Too Much! I'll just have to trust the Resistor)
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'84 300SD sold
124.128