A Discrete Puller Fan On Light

patrickt · #1 (**permalink**) 12-17-2022, 02:43 PM

From time to time, I'd like to know if my puller fan is on. With road noise, and engine noise, I can't always tell. I didn't want to make a big deal about putting a light somewhere that would bother me, and I didn't want to punch a hole in the dash, and I wanted something that I could see even in the bright sunlight, but I wanted to be able see it out of the corner of my eye without having to actually look at it. But I also wanted to be able to disable it easily. Basically I wanted something that was easily seen by the driver, but only if you're looking for it, but that wouldn't be noticed any other time, and that could be turned on and off easily. This little blue light latching push button switch mounts over in the bottom corner of the dash so it's over in a pitch black area of the door jamb. The driver can see it easily without having to look at it. It lights up blue when the puller fan comes on and goes out when the puller fan turns off. To disable the light, just turn it off by pushing it. And if you want to remove it entirely, the bracket is just held on by the dash screw. It's wired directly to the 12v+ output of the puller fan relay and protected by a 2 amp fast blow fuse. Wired this way if you saw your temperatures climbing higher than normal and your blue light is not on (because either the fan relay failed or the thermostatic switch failed), but should be, you can throw the pushers on and limp home without overheating. Not a huge project, but a fun one.

KarlzEE Bebout · #2 (**permalink**) 12-17-2022, 06:52 PM

On my ERA 2119, I wired the unused red warning light for the fan. that sits between the turn signal indicators. Many times I'd manually turned on the fan, to avoid warming up in traffic, and due to my lousy hearing, didn't realize that the fan was still running after I parked. voila!

patrickt · #3 (**permalink**) 12-17-2022, 07:03 PM

Quote:

Originally Posted by KarlzEE Bebout

On my ERA 2119, I wired the unused red warning light for the fan. that sits between the turn signal indicators. Many times I'd manually turned on the fan, to avoid warming up in traffic, and due to my lousy hearing, didn't realize that the fan was still running after I parked. voila!

Initially I was going to use a set of diodes to have the blue hi-beam light come on when the puller fan came on. But then I wanted to shut it off as well as it could become a nuisance. So then I just sat in the seat there in the garage and looked around and spotted the dark cavity over by the door jamb and hinge cover. You'd never spot it unless you were looking for it.

davids2toys · #4 (**permalink**) 12-19-2022, 06:16 PM

Great idea Patrick!
Can you provide a link or info on where to purchase the light and bracket?
Thanks

patrickt · #5 (**permalink**) 12-19-2022, 06:27 PM

Quote:

Originally Posted by davids2toys

Great idea Patrick!
Can you provide a link or info on where to purchase the light and bracket?
Thanks

Here's the switch: https://store.marinebeam.com/illumin...ired-latching/ but I fabbed the bracket from scratch. Nothing terribly fancy, just cut and grinded from thin steel plate, then drilled for the switch and a hole for the fastener. A quick black finish and you're done! Then just wire it in.

cobra · #6 (**permalink**) 12-21-2022, 12:28 AM

I always noticed the switching on and off by the pointer deflection of the ammeter.

DanEC · #7 (**permalink**) 12-21-2022, 06:37 AM

Me too. But then I would forget about it if I hadn’t driven the car for a couple of months and I would notice those wild swings in the amp gage and wonder for a moment what that was about. Since I wired in a shunt wire on the fan circuit, the fan coming on or going off, hardly makes a quiver in the gage needle.

davids2toys · #8 (**permalink**) 12-21-2022, 01:45 PM

Quote:

Originally Posted by patrickt

Here's the switch: https://store.marinebeam.com/illumin...ired-latching/ but I fabbed the bracket from scratch. Nothing terribly fancy, just cut and grinded from thin steel plate, then drilled for the switch and a hole for the fastener. A quick black finish and you're done! Then just wire it in.

Just ordered it, thanks. May have to follow up with the proper wiring and fuse you mentioned. Happy Holidays

patrickt · #9 (**permalink**) 12-21-2022, 01:55 PM

Quote:

Originally Posted by davids2toys

Just ordered it, thanks. May have to follow up with the proper wiring and fuse you mentioned. Happy Holidays

Ho, Ho, Ho... and God bless us, everyone.

davids2toys · #10 (**permalink**) 12-22-2022, 08:45 AM

Same to you

spdbrake · #11 (**permalink**) 12-24-2022, 06:00 PM

You can use a DC current sensing switch, anywhere on the Fan feed power wire. Once the switch trips (meaning the fan is actually working) it will complete the circuit to the LED indicator (grd or pwr) whichever you prefer.

There are a few thousand types and sizes of these. A bit harder to find a DC 12/24vdc one though.
This is one: https://www.amazon.com/Current-Sensi...09YN9Q9YP?th=1

patrickt · #12 (**permalink**) 12-24-2022, 07:49 PM

Quote:

Originally Posted by spdbrake

You can use a DC current sensing switch, anywhere on the Fan feed power wire.

alright. But did you think what happens when the airflow spins an otherwise still fan motor? It will generate a small amount of current through the wire....

spdbrake · #13 (**permalink**) 12-24-2022, 08:54 PM

A motor needs field excitation become a generator. But A: Even if the Motor could generate electricity, it has no current since it goes nowhere.
B: Shunt field is directional and won't measure reverse flow.

patrickt · #14 (**permalink**) 12-25-2022, 07:27 AM

Quote:

Originally Posted by spdbrake

A motor needs field excitation become a generator. But A: Even if...

I have an inductive ammeter and used it in this thread back in 2010: 300 amp X 12 volt Circuit breaker but I'm trying to think of why I would use that switch instead of just tapping directly into the feed. I suppose if the two voltages were different, or if the feed wire was really current sensitive and you didn't want to change it by firing off the next circuit, but I just don't see that on the Cobra.

spdbrake · #15 (**permalink**) 12-25-2022, 08:42 AM

I think I understand the question (or maybe not).
The Current sensing switch is an normally off(open) switch. As current flows thru (used by the fan motor) it closes at a preset amperage. The one I posted is adjustable. The Current switch has a X1 post, where you can hook a local -neg or +Pos to and also an X2 post that will continue the +power or -gnd to the LED indicator once the switch closes. Basically giving you a remote indication that the motor is using electricity.

Tapping into the feed and sending it to the the LED only tells you the power is available but not if the Fan motor is working.

patrickt · #16 (**permalink**) 12-25-2022, 09:18 AM

Quote:

Originally Posted by spdbrake

Tapping into the feed and sending it to the the LED only tells you the power is available but not if the Fan motor is working.

You're absolutely right, I hadn't thought of that. Kind of like the ignitor/valve switch on a gas stove. If it's not seeing six amps or more being pulled, by being red hot, it won't open the gas valve.

davids2toys · #17 (**permalink**) 12-26-2022, 12:08 AM

Patrick, I ordered the indicator light you used with the link provided. So will it work? Also, I have a voltmeter, not an ammeter like you have.
Edit: Just reading that thread, I think I misunderstood you, I thought you were saying you had ammeter in your car as a gauge, not understanding you meant a tool. Maybe you have a Voltmeter Gage like me?

patrickt · #18 (**permalink**) 12-26-2022, 05:44 AM

Quote:

Originally Posted by davids2toys

Patrick...

Yes, your light will work perfectly. Spdbrake's point, and it's a valid one, is that for truly mission-critical or life-death situations you should check for the presence of a load (like a running fan) on the line as opposed to just tapping in to the line. For example, a broken wire right at the fan will still have the blue light come on even though the fan is broken. For our cars that's not a terribly big deal. But for the gas stove in your kitchen it would be a really, really big deal.

And I have an ammeter on my dash, not a voltmeter. I also have a fancy clamp on inductive ammeter as a tool in my garage for doing electrical work. It's an easy way to measure current without having to cut any wires. If you click on the little link in my previous post it has a picture of it.

patrickt · #19 (**permalink**) 12-26-2022, 08:39 AM

There is an advantage to having your blue light wired directly into the fan feed wire and not into a current trigger device and that is troubleshooting. Since this new circuit is not controlling any mission critical or life-death condition (like turning your natural gas supply on in your oven even though the ignitor is broken) all it's really doing is alerting you to whether voltage is being sent directly to your fan. Now, with a nice quality SPAL fan, and a decent wiring installation, the odds are overwhelming that if the blue light is on your fan is on and, unless the little blue light burned out or blew its fuse, if the light is off then the fan is off. But what if the fan is off and the blue light is on and your engine is hot? Then that would tell you the fan has failed but the relay is working. It also tells you the thermostatic switch is working. A current measuring circuit wouldn't tell you this, it would just leave the bulb off and you'd have to manually test both the relay and thermostatic switch.

HTM101 · #20 (**permalink**) 12-26-2022, 02:30 PM

About 4 years ago I was idling in traffic for quite a while, comfortable that my puller fan was working fine because I had switched it on with a manual dash switch. Eventually I noticed the engine temp was higher than it should be. The fan had switched off because a thermal breaker had reacted.

Subsequently I upgraded the wiring, used a different breaker and added a light that illuminates when I switch the fan on from the dash, or when the thermostat triggers the fan on.