Electric Fan Wiring Question!

[jrhone]

I used the diagram in the faq for electric fan wiring. Everything works great EXCEPT the bypass switch. I have a switch to turn on the fan regardless of the temp. It works fine. I used a lighted switch that turns on when you switch the fan on. I tapped into the radio power for the light in the switch. When I use the switch it all works perfectly, but when the fan comes on from the temp switch it blows the fuse for the radio. Its as if there is power coming back into the switch and then into the line I tapped into for the light. So I thought...add a diode and a fuse on the so power cant go the other way....then I thought maybe tap into the same power the fan is using...but would I run the risk of causing a loop in the circuit? If I use a diode what power is needed? Right now I dont have the light wired...but I'd like to! Is there something I need to do to wire a lighted switch?

[Swiftus]

If you add the diode across the coil circuit, as long as it is pointing the right way, it *should* prevent the voltage spike that occurs when the field collapses in the coil. This may be what is blowing your fuse.

To be safe, however, I would look at the contacts on the underside of the fuse panel and see if they are corroded. These are often overlooked and are a pretty easy fix for many electrical issues.

[Tommy]

So you used this diagram - right?

What exactly did you change? You should have the power line going through 30-87 and control line 85-86 clearly distinct. You can change the telltale light to control side but then it wont tell if the 30A fuse is blown. I'm afraid your connection somehow pulls power from the control side.

Tommy

[jrhone]

So you used this diagram - right?

What exactly did you change? You should have the power line going through 30-87 and control line 85-86 clearly distinct. You can change the telltale light to control side but then it wont tell if the 30A fuse is blown. I'm afraid your connection somehow pulls power from the control side.

Tommy

I changed NOTHING in the diagram. The switch I used though has a light on it, so it pulls 12v power to turn on its light when you use the switch. That works just fine EXCEPT when I DONT use the switch and it turns on with the temp switch. Then the fuse blows on the line I pull 12v power from for the switch.

[Tommy]

The switch you have - is there 3 prongs so that one is for the light?

If yes which line did you have the one for the light connected?

T

[jrhone]

Yup...3 prong. 2 are for the ground...one is power for the light....its a lighted SPST thats rated for 240V DC and the bulb is 12V DC. So here is what it looks like....I have no diode and it shows the 12v+ going to the switch. Its that fuse that constantly blows when the fan turns on with the temp switch..so it seems I am getting a surge from the fan when it kicks on (or off).

[Schweineback]

Why no take the + from the 87 pin (like on the drawing) and have the whole system of the electric fan locked away thight behind one fuse? Keeps it simple.

[Tommy]

It's starting to look like I can't help from here. Maybe someone else gets an idea.

Anyway I don't believe in surge or something like that. What bothers me is that if the connection is like you describe there should be no difference whether you turn the switch or the thermoswitch engages. The connection in your switch is probably like this.

T

[jrhone]

Why no take the + from the 87 pin (like on the drawing) and have the whole system of the electric fan locked away thight behind one fuse? Keeps it simple.

Thats my question...should I take it from there?The reason I didnt in the first place was that its not close...but since I used that for my light....I can use it for the switch just as easily....The only thing that concerns me is if I was blowing a fuse before....would that just blow my fuse on the electric fan? Or would I blow the relay because its between the +12v and the fuse? Or is there any danger to the $110 fan?

[Fishhead]

Thinking out loud..

If your wire that runs to the SPST switch is on the "other" side of the switch (as shown in this photo shop pic), then I think when your fan kicks on with the thermo switch, you would blow the fuse.

You shouldn't need a power source to the SPST as it gets its power through the relay from #86 to #85 and the switches (thermo and toggle) are on the "ground" side of the power switch supply. The schematics shown above all have the "switched power source" connecting to terminal #85 and use #86 as a ground to activate the relay (push power from the battery through the fan)