HELP! Billet Button Wiring for Footbox Blower

[dbo_texas]

I'm struggling to get this button working the way I want and hoping someone here can help. I'm using this button to control my footbox blowers (via a relay), and ideally I would like the LED to light up when either the button is pressed or the parking lights are on. I thought this method below would work, using diodes, but unfortunately it does not. The lighting function works exactly as I want, but the relay coil won't trigger and therefore the fan won't kick on. It's almost like going through the LED for the ground path (relay pin 86) doesn't get a good enough ground. It's very strange....because the LED kicks on which means it does have a good ground, and yet the relay won't trigger.

Just for clarification, the black wire on the switch is the LED common anode (+), and each color LED has a cathode wire ( - ). So if you want to use the blue LED, you ground the blue wire, for the red LED you would ground the red wire, etc. In my schematic I used diodes to make sure there is no current reverse flowing. I've now tried re-wiring this multiple ways, all with no success to get the desired LED + blower on combo. The part that really confuses me is that logically it seems like this should work --> the LED common anode (+) black wire can get power from either source (parking light OR from the relay coil pin 85). This is confirmed because the LED works for either condition. But the relay just won't trigger (as if the coil ground circuit isn't closing)..but if the LED is coming on, then the ground circuit is working. If I connect the orange wire (NO) directly to the blue wire (LED negative), the relay will trigger and the blower will come on, but then I lose the ability to turn on the LED when the button is pressed (the parking light still illuminates it). I've wasted so many hours messing with this stupid button, hoping someone has a setup similar to this and can help me out. I must be missing something obvious.

https://thefactoryfiveforum.com/attachment.php?attachmentid=210562&d=1739904747

[D Stand]

Looks like you are providing both sides of the relay coil with a + source, which is why it is not working. Move your switched output (purple) to coil + (86) and ground the coil - (86) and it should work. That is if you are intending to only run your fan when the parking lights are on..

[dbo_texas]

Looks like you are providing both sides of the relay coil with a + source, which is why it is not working. Move your switched output (purple) to coil + (86) and ground the coil - (86) and it should work. That is if you are intending to only run your fan when the parking lights are on..

Can you explain how pin 85 is getting a + source from the switch button side? The point of adding the diodes is to prevent the parking light from providing 12V+ to pin 85. Or am I not understanding how diodes work? I know they only allow current in one direction. So I thought they would prevent what you describe (and also prevent the relay coil from powering the parking lights when the button is pressed). To clarify, I do not want to only power the blower when the parking lights are on. Should be able to turn them on any time IGN is ON.

[D Stand]

I miss interpreted your diagram at first. Looks like you do have the diodes in correctly. In general it looks like the LED in the switch is not letting enough current through to pull the coil in. I would try to add another diode from orange to blue to allow a direct path to ground but still allow LED to light

[F500guy]

I will tell you why it is not working, but not sure I understand the goal for the light function.

It will not work because the voltage drop across a diode is .7 volts in this case. So, at the junction of the 2 diodes you have (Source voltage -.7) say for example if source was 12, then diode junction would be 11.3 volts. The remaining voltage would be dropped across the led. So you really have <.7 volts difference between source side of the coil and relay junction, not enough to operate the relay.

[F500guy]

You could disconnect the Diode from the orange and instead connect that end to 87 terminal, so when the relay operated the LED would be powered. Connect the orange to ground so it operates normally when active with the switch. Make sure the wiring and switch can handle the 15 amp supply.

[dbo_texas]

You could disconnect the Diode from the orange and instead connect that end to 87 terminal, so when the relay operated the LED would be powered. Connect the orange to ground so it operates normally when active with the switch. Make sure the wiring and switch can handle the 15 amp supply.

Thanks this is really helpful! Is this what you are describing? Basically run the output (Pin 87) of the relay to power the LED & blower? Seems to me this is the fix. I'll have to run 2 more wires from the relays (one for DS, one for PS) up to the dash buttons but I think I have some spare pins in one of my custom harnesses that I can do this with. Does this schematic look correct per your suggestions?

https://thefactoryfiveforum.com/attachment.php?attachmentid=210723&d=1740337540

[F500guy]

Yep

[Nigel Allen]

Thanks this is really helpful! Is this what you are describing? Basically run the output (Pin 87) of the relay to power the LED & blower? Seems to me this is the fix. I'll have to run 2 more wires from the relays (one for DS, one for PS) up to the dash buttons but I think I have some spare pins in one of my custom harnesses that I can do this with. Does this schematic look correct per your suggestions?

https://thefactoryfiveforum.com/attachment.php?attachmentid=210723&d=1740337540

This circuit will work, but has one issue. When fan is not in use, but is free-wheeling, i.e. pushed by the wind when the car is driven, it will generate power, which will feed back and cause the LED to light. This can be over come by installing a 5 pin relay with 2 NO outputs, or by installing a high current diode in the supply to the fan (between the relay contact and the fan motor)

Cheers,

Nigel

[dbo_texas]

This circuit will work, but has one issue. When fan is not in use, but is free-wheeling, i.e. pushed by the wind when the car is driven, it will generate power, which will feed back and cause the LED to light. This can be over come by installing a 5 pin relay with 2 NO outputs, or by installing a high current diode in the supply to the fan (between the relay contact and the fan motor)

Cheers,

Nigel

Thanks Nigel - I hadn't thought of that. If I go the 5-pin relay route (w/ 2 NO contacts), I guess the idea is the blower and the LED are driven with independent PWR OUT from the relay? That way no matter what happens with the fan, it doesn't influence the LED. I did a quick search on Amazon an maybe I'm not searching for the correct terms but I don't see any relays with two NO contacts. Just one NO (pin 87) and one NC (pin 87a). Is there a specific name for these?

The blowers I'm using are 2.5A. I have these 5A diodes (https://www.amazon.com/dp/B07XDJGDQP?ref=nav_custrec_signin&ref_=cm_sw_r_cso_cp_apin_dp_QGP4JJWWZBB2BD7NNQEM&social_share=cm_sw_r_cso_cp_apin_dp_QGP4JJWWZBB2BD 7NNQEM&peakEvent=4&starsLeft=1&skipTwisterOG=1) - would these be sufficient if I want to go that route instead of changing the relays? It would definitely be easier to put some diodes in-line with the blower +12V feed vs. swapping the relays out.

[Nigel Allen]

G'day Darryl,

I had assumed that this was for your cooling fan where the negative needs to be switched for the relay. I will redraw a circuit for you tomorrow when I get into work and send it through.

If you decide to go with the diode route, you may need to parallel them to get 10 amps, to allow for the motor starting current.

Cheers,

Nigel

[F500guy]

Good Idea Nigel, I did not think about a windmilling fan. Interested to see your recommendation, 2 diodes in parallel?

[dbo_texas]

OK folks - I was able to test the re-wired circuit from post #9 (https://thefactoryfiveforum.com/showthread.php?50833-HELP!-Billet-Button-Wiring-for-Footbox-Blower&p=575313&viewfull=1#post575313) and confirmed it is now working exactly as intended.

-pushing footbox fan button turns on the fan AND the button LED
-turning on parking lights/headlights will also turn on the button LED

Still waiting for more info on the parallel diodes connected to the fan motor to prevent illuminating the button when the blower fan is free-spinning. I think it just means putting two diodes in parallel with each other, but in series with the fan power wire, with the current direction flowing to the fan only (i.e. fan can't drive current towards the LED). But I have easy access to the fan power wire so I can add those later.

https://thefactoryfiveforum.com/attachment.php?attachmentid=210869&d=1740543656

Thanks to everyone for the input and suggestions! Feels good to finally have electrical 100% checked and working!

[Nigel Allen]

G'day Darryl,

Sorry it took me a while to get this to you, wife had flu. This circuit will do the job nicely, and is a bit simpler.

210872

There is also provision for an optional resistor to give a lower brightness when parking lights are on, but blower is off. (fancy) Probably would need 330 - 470 ohm resistor depending on brightness required.

Would also recommend using a relay with flywheel diode inbuilt, to prevent possible over voltage to LED.

Cheers,

Nigel

[Nigel Allen]

Good Idea Nigel, I did not think about a windmilling fan. Interested to see your recommendation, 2 diodes in parallel?

I suggested 2 diodes in parallel due to motor current. You can just use one, but will need to be 15amp rated, to be protected by the 15amp fuse in your drawing.

Cheers,

Nigel