ATTENTION: All UrQ Owners!

[Robert Houk - SMCC Bos Desktop Hardware <rdh@UrQ.East.Sun.COM>]

Some time back I posted a "fixit" tip on derouting the radiator fan
through the A/C/Fresh-Air circuit (since it tends to melt the A/C/
Fresh-Air fan fuse/relay panel) and rewiring to run through the
main fuse/relay box.

Well, don't do that either, the main fuse panel will melt.

Re-route the radiator fan to have its own dedicated feed wire, bypass
ALL AUDI fuses!

Gawd I could learn to *HATE* these cars . . .

I don't know how this applies to later UrQ/fuse panels, but for those
of you with the 15-fuse main fuse/relay panel, with 6 auxilliary fuses
modularly mounted above the main panel, with a secondary fuse/relay panel
mounted in the glove box -- heed this warning. The radiator fan high
speed setting (A/C engaged, or overheat) will melt the stock Audi fuse
and relay sockets used. Note the fuse itself doesn't melt, just the
fuse holder! (although when I went to disengage the #15 fuse, it in
fact disintegrated in my hand; I guess the fuse panel gave its life
to protect its darling baby fuses . . .).

Background -- This is for early UrQs, I don't know if or how it would
apply to other Audis of that vintage, but y'all might want to pay heed
and check out your cars for this problem as well . . .

The stock system has three radiator fan speeds, ignition off ("low"),
ignition on ("normal"), and A/C engaged or overheat ("high").

Low, normal, and overheat-high are fed via the #15 fuse in the main
fuse panel, with low/normal being governed by a relay bypassing a
resistor to fed one of two fan motor windings. Overheat-high is fed
by a second relay feeding the second fan motor winding.

A/C-high is controlled by the secondary fuse/relay panel mounted in
the glove-box (against underside of dash bottom); there is one fuse
and three relays. From left-to-right (facing forwards to front of
car), the fuse controls the fresh-air fan, the A/C power (to A/C
clutch, etc.), *AND* A/C-high radiator fan feed, in parallel with the
overheat-high fan relay mentioned above. Next to the fuse is the
master relay (controlled by the "load reduction relay" in the main
fuse/relay panel, which is switched by the ignition switch, off for
"Off" and "Start", on for normal running) for A/C/fan, then (I forget
the order) the A/C control relay (controlled by the A/C microswitch on
the center console control cluster), and the A/C thermostat/clutch
relay.

If you have not already done so, I *strongly* recommend you inspect
the secondary A/C/fan fuse/relay panel for meltdown.

(Also note that the fresh air fan is nominally fused by the SERIES
connection of the main fuse box fuse [I misremember the number off-
hand, maybe #8??] with the secondary A/C/Fan fuse in the glove box.
The former is in the owners manual, the latter is not mentioned any-
wheres that I have seen . . .)

I rewired my A/C to switch the overheat-high relay, rather than di-
rectly try to power the radiator fan (through an additional dozen feet
of Audi wiring, replete with Audi crimp connectors...thereby helping
drop the voltage to protect the radiator fan, as well as helping to
defrost the underside of the dash) so as to not melt another A/C/fan
fuse panel. This directed all radiator fan "high" speed through the
main fuse panel #15 fuse (the one the owner's manual tells you about).

This subsequently melted my fuse panel around the #15 fuse, intermit-
tently shorting it to the rear-window-defroster circuit (and killing
the battery too! Since the rad fan is unswitched +12...). Of course
this led to the interesting loop whereby if I switched on the rear
window defroster, it now would feed power back into the ignition-
switched +12 in the main fuse panel, enaging the load-reduction relay,
which would activate the A/C/fan master relay, which fed power to the
A/C relays, which in turn could then activate the "high" speed radiator
fan relay, thus ensuring the defroster of a continuing source of +12,
for as long as the battery lasts...

So far, the high-speed fan relay (and mount/socket) shows no signs of
incipient melt-down.


To help avoid a damned-inconvenient situation (if not outright dangerous,
as things start melting . . .), I *strongly* recommend you consider
rewiring to provide the radiator fan high speed with its own dedicated
10ga feed circuit. Or just don't use your A/C . . .

I run a dedicated separately-fused 10ga from the battery to the high-
speed fan relay, bypassing completely the main (and secondary) fuse
panels.

Harumph!

					-RDH

P.S.	All'uh'youse UrQ owners out there, I would be interested in
	feedback on the state of your car vis-a-vis the above -- how
	many of your cars shows meltdown damage (or no problems at
	all)?