Bryan,
The relays seem to be working just fine, but I am going to use your
suggestion for wiring the A/C relay in parallel.
As for the position of the thermoswitch, I see your point, but the truth
is that the thermoswitch doesn't turn off at the same speed that it
turns on. The tests I did on the stove top with a temp probe and a ohm
meter were as follows.
Low ON = 183
Low OFF = 156
High ON = 192
High OFF = 165
I don't know how accurately these test tell what happens during semi
constant temperatures achieved by the thermostat opening and closing,
but it does tell me that the on temps are different than the off temps,
which I think will keep the cycling down. I do know that older mid '80s
Saabs controlled their fans this way.
My real in truck observations are still minimal. Today the outside
temperatures were very mild. The fan would go on in stop and go traffic.
When I was freeway driving it stayed off until I got off the freeway I
then drove for about a mile and was at work and the fan ran for about 5
minutes after I parked. I haven't had any off on fan cycleing except for
when the engine was cold and I had the A/C on. As the fan clutch cycled
off and on so did the fan.
Thanks for your input.
Bill
-----Original Message-----
From: owner-dakota-truck@bent.twistedbits.net
[mailto:owner-dakota-truck@bent.twistedbits.net] On Behalf Of M.Bryan
Galloway
Sent: Wednesday, April 23, 2003 7:03 AM
To: dakota-truck@dakota-truck.net
Subject: Re: DML: Viper Fan Saab temperature switch
This is supposed to be part of my previous post, Oooops.
I have two questions, one about the 2nd wiring diagram and the other
about
the placement of the thermostatic switch.
1st: You drew the a/c fan control relay in series with the a/c comp
clutch
relay. I think its possible that the combined resistance [impedance,
actually] MAY be sufficient to reduce current flow to the point that the
relays act erratically, or possibly that the voltage drop across the
first
will cause the 2nd to go erratic. Wouldn't the coils in parallel off the
pcm
provide full voltage/current to both and operate the way you want them
to?
2nd: You said you installed the thermostatic switch in the upper radi
ator hose. Every liquid cooled volkswagen I've seen puts that switch in
the
lower area of the radiator near the radiator outlet [lower hose]. Won't
placing a 180 switch just downstream of a 180 t-stat have the fan come
on
when the t-stat opens? I believe the temp controls are set up to work
in
stages; I.E. high temp leaving the engine opens the t-stat to provide
radiator cooling, high temp leaving the radiator enables the [low-speed]
fan
circuit to increase radiator cooling, and continuing temp increase
leaving
the radiator enables the the high-speed fan circuit. Won't having the
switch
in the upper hose cause increased cycling of the t-stat/fan? These
question
are purely theoretical as I haven't done the install myself, yet and I'm
trying to anticipate/head-off operational problems
M.Bryan Galloway
For any thinking person the title "Criminal Justice System" should have
been
sufficient warning. L. Neil Smith
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