[TR] Spal Fan Installation
tr3driver at ca.rr.com
Sat Jul 20 10:27:59 MDT 2019
I believe it could be done, but not with standard electronics.
Most fan controls are looking for a contact closure, so obviously they aren't going to work with a gauge sender.
Even with a fan control that expects a variable resistance (like the gauge does), it will "read" that resistance by passing a current through it, and measuring the resulting voltage. The gauge does the same thing. But with current from two sources, the voltage will be much higher, which will confuse both fan and gauge.
One way around that is to build your own fan controller that only looks at voltage. Not hard to do, one IC, one transistor, and a handful of resistors will do the job. But probably more than most want to tackle. It also makes fan operation depend in the gauge, which might not be desirable.
FWIW, since my car lacks the optional heater, it was easy to mount a fan sensor in the heater return fitting on the water pump housing. Although I did not try it, I believe you could put a tee in that hole, and connect both heater return and fan sensor. Heater operation would affect the fan to some extent, but I think not enough to matter.
On 20 July 2019 11:08:18 GMT-05:00, TERRY SMITH <terryrs at comcast.net> wrote:
>I'm still researching this but thought I'd ask anyway. I've a Spal
>pusher fan with a thermostat from years ago I never installed.
>Deciding to install it because the 3 is running fine at thermostat temp
>on the road, but shortly after I shut down in this heat it barely
>starts again and runs rough until the float bowls clear. Letting the
>fan run after shut down ought to help keep the float bowls from
>Awhile ago I installed SunPro electric temp guage and sending unit. So
>question. Can you use the same temp gauge sending unit as the temp
>sensor for the fan also? The temp gauge sensor uses some sort of
>resistance affected by heat, I suppose, but whether the fan reads it
>the same as the gauge is puzzling.
>Thanks, everyone (again!)
>Terry Smith '59 TR3A
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