The Stovebolt Site Forums The Shop Area The Electrical Bay Dash light knowledge (wiring) for activated electric fan on AD with 350?

Would like to know how to wire up a dash light for when my electric fan is activated in my '51 AD? The way that I have it now...it seems to work, but it bleeds off to the dash light when I'm driving down the road. And its "ON" when I going down the road at times. Do I need a resistor put in-line or what? Or some kind of a diode? Have a 350-V8. (The light just lets me know as to when the electric fan is activated and working...and at the temperature that I have it set. A manual dial. Would like some help please. Thanks, diditanole

diditanole,

I think I've seen this problem mentioned on here before. I'm guessing your dash light is connected to the load side contact on the relay. When the thermostat calls for 'cool', the relay closes, powers the fan AND lights your tattle-tail dash light.

If air passing through the radiator spins the fan, the motor turns into a generator, and through that connection on the relay powers your tattle-tail light.

You might have to add another light in series to act as a resistor, or add a resistor...or power your tattle-tale light off off the coil on the fan relay. Powering it this way wouldn't be 100% like it is now but unless you are a real unlucky fellow, should be 99% fool proof.

There could be someone along soon with a much simpler solution, lets see who pops in.

Stuart

I asked the same question last summer and never got a good solution. I've just learned to distinguish between when the fan is running (bright LED) and when the wind is pulling it (dimmer LED).

I thought about wiring to the trigger side of the relay but that won't tell me if the relay goes out.

You might try triggering the coil of a second relay off of where you have the led hooked up now. Then you could turn on the led through the contact of the second relay. You will have to find a relay that will trip from the 6 or 12 volts but not trip on the voltage generated by the fan. I guess you could spin the fan and measure the voltage and current generated by the fan. Just waht I would try. I do however try a lot of crap that doesn't work.

Neil

I use my fan as a "PUSHER" because there isn't clearance for mechanical fan set-up. I have a 16-inch Hurricane fan. And you know, I never thought of the wind turning the fan and as a generator...so to speak. I have "HEI" in my 350. Hmmm, maybe a second relay installed, huh? And yes, the LED dash light is "DIMMER," when the electric fan is "NOT ON," and I'm driving down the road. And it is brighter when it is "ON." The relay is a Bosch. I like the term: tattle-tail light!
I'll wait and see who else pop's in on this thread. Many thanks to all who responded to my thread, and the knowledge ...diditanole

diditanole...

diditanole,

If you are determined to kill that dash indicator light when the relay is open, you could see if Bosch makes a double pole relay that fits into the same base and wire the tattle-tale light on the second set of contacts that would be powered from the first set when the fan relay was ON.

This would indicate power to the load side of the relay, proving that there was power applied to the fan, but would be open when the relay was OFF...hence, no connection with the motor turned generator.

Bosch surely makes a automotive DPST relay, even if you had to get a new base/socket.

The easiest answer would be to power your tattle-tale light from the relay coil and assume the fan has come on. Your temp gauge would be the last word of proper fan operation.

Stuart

Atomarc,
Yeah, I have a bosch relay switch for my 16-inch electric fan. Also have alternator in place. I'll have to try something different. Because I want that "tattle-tale-light" in place. Thanks for all your help. I'll keep my eyes open for knowledge. again thanks...diditanole

Bosch does make a relay with two independent '87' terminals. Terminal 30 is battery feed, terminal 86 is input from the thermostat switch and 85 is a ground for the relay coil. I haven't loaded my John Deere pars info on this computer so I can't give you a Deere P/N.

Do not get the relay with a 87a terminal--it feeds battery voltage to the 87a terminal when the relay coil is NOT energized. This relay (with the 87a) is a SPDT.

automarc and Racecarl,have got it.Get a relay with more contacts,one set will operate the fan,an other set to operate the light.

BC52,

Yes...that's the answer. I mentioned that a few posts ago, stating that Bosch surely made a DPST relay. I looked for one and lo and behold, they don't seem to make one. I couldn't fine anyone that made a DPST automotive relay.

The obvious answer would be to stick two SPST relays side by side which would accomplish the same thing...but not quite as neatly.

Stuart

Potter/Brumfield,make relays.Maybe they make one that has the same values you need,or if at second relay is needed it can be concealed.

The relay you need is a 5 blade double make and break. The fan would be connected to contact 87 and the LED to 87b. The two contacts are isolated from each other till the relay operates and provides power to them both via contact 30. Take a look at part number R30BD on this page.
http://www.vehicle-wiring-products.eu/VWP-onlinestore/relays/relays.php

You should be able to find a US supplier for the relay which is a standard Bosch type.

Stuart.

Thanks... diditanole

You don't need any extra poles on that relay, just isolate the light socket from ground and connect it across the coil terminals. When the coil is energized by whatever turns it on, the light will be too.

thanks, diditanole