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Re: Water Wetter?
- To: email@example.com
- Subject: Re: Water Wetter?
- From: firstname.lastname@example.org (Robert D. Houk)
- Date: Thu, 15 Sep 1994 16:49:36 -0400
- Cc: email@example.com
- In-Reply-To: <9409151250.AA11710@alpha.zk3.dec.com> (message from Andrew Duane USG/PE on Thu, 15 Sep 1994 08:50:47 -0500 (EDT))
- Reply-To: quattro
- Sender: quattro-owner
Thanks for the information. I feel a little better about potentially
dumping this stuff in my radiator. I think (actually: thought) the
problem might just be an old radiator that is starting to crud up a
little bit. I'm closing on 100K miles, and they do that.
I just broke 100K...
But, after your mail, I've changed my mind. This is exactly what
happens to me. When I'm cruising, or have the A/C on, all is fine.
But, doing 30 MPH in traffic for 1 minute, or sitting at a light or
two, and my temperature moves up a full 1-1.5 marks on the gauge.
Eventually, after going up almost 2 marks, the fan comes on, and the
temperature comes down a little. It takes a LONG cruise to make it
come down to normal, or I turn on the A/C for a minute.
This sounds a lot like your problem.
So, what relay bank was this, and where should I poke?
Up under the dash, driver side, above the "normal" fuse/relay box, is a
bank of relays (actually mounted to the underside of the top of the dash).
I think (vaguely remember) that there are six relay sockets. I kinda almost
remember that the order is, left to right facing forward:
radiator-fan "high" speed
hot-start pulse relay (big sucker)
radiator fan normal speed (resistor bypass)
xxx (empty on mine - maybe rear wiper?)
It's reasonably-accurately spelled out in the aux factory documentation.
There is a small-guage (18?) brown wire that is the common ground for
everything but the fuel-pump relay (and maybe the xxx?? -- anyways, most
of the relays share this common ground wire, and I vaguely recall it's the
only brown wire "up there" that threads 'twxit the sockets, and is small-
guage). I think maybe the injector-cooling fan does not use this ground,
as the head-mounted sensor closes to ground to activate the relay, but
again this is hazy in my mind. Look for the shared light-guage brown wire!
You should be able to feel the radiator-fan normal relay click in when you
turn on the ignition (I think it switches off during engine-start cycle).
It always stays engaged (except maybe start) since what it does is short
around the dropping resistor for the radiator-fan low speed (ignition off)
Another check you can do is to warm up the engine until it's good'n'hot,
(i.e., radiator fan running) then switch it off. The radiator fan should
be running fairly quietly. Switch the ignition to ON and the radiator fan
should speed up noticeably (subjectively, I will say "double" the air and
noise, plus or minus an order of magnitude) as the radiator fan relay kicks
in and bypasses the resistor. Switch the A/C on and the radiator fan should
again speed up noticeably (although by a smaller "increase"), to the accom-
panyment of a variety of relay clickings from the glove-box area... The
high-speed radiator-fan-relay should not have activated during any of this
(unless you got it REALLYGOODNHOT!).
Fuse 15 (right-most) is the fuse that powers the radiator fan for low and
normal speeds; it also provides power for the high-speed-relay (which is
triggered [in theory] by a thermal switch in the return water line from
the bottom of the coolant resevoir to the bottom of the radiator feeding
back into the engine -- how nifty, a [admittedly-low-volume] coolant cir-
cuit that completely bypasses the radiator!) High-speed fan power from the
A/C system comes via a SEPARATE fuse located above the glove box, just to
the left of three A/C relays. [As an aside, this fuse also powers the
fresh air fan motor! Owner's manual notwithstanding!]
I made three mods to my radiator fan circuitry: I ran a dedicated 10ga from
the battery to the fuse-15 input terminal; I re-routed the A/C circuit for
the high-speed fan to switch the high-speed-fan *relay* instead; and I added
a "cute little toggle switch" to switch on the high-speed-fan relay directly
(mostly to speed up the cool-down cycle for a hot engine - rather than wait
for the engine to heat up enough to keep the radiator fan normally engaged,
I can force the engine temp down another 30 degrees (F) or so! [thermostat
opens at 180; radiator fan thermoswitch closes around 200-210 or so]). The
dedicated 10ga wins me a volt or so extra (depending on which particular
circuit/path is in use) to the radiator fan (and offloads the main fuse box
as well, keeping it cooler). It's easy to replace, it's the right-most upper
heavy-guage red wire on the back of the fuse-panel, connecting to the #15
fuse position via a [drumroll!] crimped-on spade connector. Pulls right off
too . . .
The wiring/relays are fairly accessible, once you pull off the whatever-you-
call-the-plastic-thingie. You can easily get in under the steering wheel to
fondle the relays, and carefully insinuate your voltmeter probes to the re-
lay socket pins. I ended up using small insulated alligator clips/wires -
connect one end to the relay pin you want, the insulation protects against
shorting to an adjacent pin, and you can then "leisurely" measure the what-
ever, switching the ignition on/off and the like. Many of the "electronics"
stores carry nice sets of (e.g.) 10 multi-colored wires with these little
insulated alligator clips on each end. Very handy. [I'm sure that Radio Shit
has them!]. You can also use them to "force" the relays on as well . . . I
carry a couple in my tool box in the trunk! They're fairly light-guage wire
(22ga??), so don't try to run the radiator fan itself with them!