Bill,
Thanks for doing the diagram with the manual switches also.
Maybe you can clear this up for me. When the temp reaches 192 degrees, the
fan goes from low to high, correct? When the temp drops down to 183, does it
kick back to low or does it stay on high till it drops to 165 and then go to
low? I'm trying to figure out if my Viper fan will run continuously on high
in FL summer with the air on if it can't drop the temp down to 165.
Won't it always run on low if the temp stays above 156 degrees?
Thanks for any help,
James
In a message dated 4/24/2003 3:51:50 AM Eastern Standard Time,
bill@nissley.com writes:
> 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
>
> mbggt@hotmail.com
>
> For any thinking person the title "Criminal Justice System" should have
> been
> sufficient warning. L. Neil Smith
>
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