North American Turbocoupe Organization



Fan Lights
89gted Offline
Senior Member
#1
I think one of my fans failed yesterday. I will track down the problem, but I had a thought that I need a little help on. I would like to mount a led indicator for each fan on the instrument cluster next to the temp gauge. I was thinking that if the led was wired in parallel with the ground side of the fan motor, then it would glow if there was current going thru the fan. This could tell you if they were working when your temp gauge was rising. Any thoughts?
[Image: th_TC016-PaintShiney.jpg]

Another proud dues paying member.

88TC, 210K, Black/Raven, Auto (may change), 140 speedo (by Jeff K), trip computer, 3G, cold air K&N, improved IVR, new AC system, new windshield & 360 tint, new sensatracs all around, interior cleaned up like new, now for the outside....
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Pete D Offline
Administrator
#2
I have some text and diagrams originated by JoeCool about this very feature. I haven't installed it yet so It's a use at your own rick thing, but I'll send them if you want
Pete Dunham


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89gted Offline
Senior Member
#3
Thanks for the diagrams Pete (and JoeCool). That may be the way I end up going. What I was really talking about is indicator leds that light up only when the fan is really, really, really running. You could have power to the fan, but if the motor had crapped out, it's not really running. JoeCool's override switch setup is great, and I will use it, but I want the lights to be true indicators of functioning fans. Would the leds light up if they were wired into the other side of the fan?
[Image: th_TC016-PaintShiney.jpg]

Another proud dues paying member.

88TC, 210K, Black/Raven, Auto (may change), 140 speedo (by Jeff K), trip computer, 3G, cold air K&N, improved IVR, new AC system, new windshield & 360 tint, new sensatracs all around, interior cleaned up like new, now for the outside....
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Martin Offline
Senior Member
#4
Pete. I was just debating this update on my fan switch/indicator light. ( I only wired in one fan at that time)When I wired in my switch, I bought a dash light from Kenworth trucks, that has a "Fan" insert on the face, so when it lights up, it says fan ( just one of those little touches, and Kenworth has a very nice collection of lights with name tags on them). This thread got me wondering? I was going to run lead from the fan positive side (the one I am currently running switched) back to my dash light. I do not have my Elect Schematics handy, but is the negative side switched at the relay, or is it direct to ground and only the positive switched? What I am going to do is run a double cable from the fans back into the dash, so in the future I can add the second light if I want it. Then I can watch when the fans kick in. Current thought is that it would be nice to run from the negative side, to reduce the chance of shorting out the fan wiring if the cable gets damaged at some point. IF the fans(s) ground is direct to chassis, then I guess I will have to run from the hot hot side of the fans back, and make sure I have routed the cable very carefully!
Martin
Stock 87, no mods, Black with the grey interior.
Boost High, Fly Low
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Joe F Offline
Posting Freak
#5
The fans on 87/88 TC's are switched on the hot (+12V) side by the IRCM relay. The fan negative lead is connected directly to ground.

Actually monitoring the fan operation, not just the applied voltage, could be accomplished in a couple of different ways. Easiest (a relative term Big Grin ) would be a current sensing circuit in the negative lead of the fan. This could be accomplished by using a series resistor to develop a small voltage while the fan is running, and using that small voltage to control an electronic switch that in turn activates the fan lamp on the dash. The sensor has to be a specifically-sized, probably high wattage resistor. If you can measure the actual current draw of each stock fan (JR's fan is not stock) I could calculate the value required and design the switch circuit as well. The second way of monitoring would be to actually monitor the fan operation using an optical sensor of some sort, which IMHO would be a little overkill.

Martin, if you're going to run a sense wire into the car from each of the fan leads, I suggest using a 100 ohm, 1/4 watt resistor at the point of actual connection to the fan power wire. That way your sense line isn't able to source any more than a little over 100mA and shouldn't be a potential fire hazard if it gets shorted to ground accidently; it should act like a fuse.

HTH
JR's Place - My '87 Turbocoupe
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89gted Offline
Senior Member
#6
JoeCool, my TC is in the shop until sometime next week (see AC Woes). I'm also getting the windshield replaced and a full tint job next week. Once I get the car back, I'll measure that current draw on each fan and let you know. Being able to turn the fans on at will is a good thing, but I think true fan operation indicators is even more important.
[Image: th_TC016-PaintShiney.jpg]

Another proud dues paying member.

88TC, 210K, Black/Raven, Auto (may change), 140 speedo (by Jeff K), trip computer, 3G, cold air K&N, improved IVR, new AC system, new windshield & 360 tint, new sensatracs all around, interior cleaned up like new, now for the outside....
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Jeff K Offline
Administrator
#7
Remember that even the 10ga wires to / from the fan has some small resistance. Since the fans run with currents of around 20A, it is likely that there will be a voltage drop of 10s to 100s of millivolts either between the IRCM and fan, and/or fan and ground. A simple comparator circuit using a comparator chip could be used to compare the drop on either the power or ground sides to a reference voltage to see if the fan is running.

Another approach would be to use a Hall effect sensor or Hall effect switch mounted on the wire to measure the magnetic field produced by the wire when it carries current.

I have indicator lights (12 V LEDs) that just monitor power applied to each fan. For me, that is enough.... if an LEDs indicate the one or the other or both fans are running, and the motor is still heating up, I can always pull off the road, pop the hood, and check things out.
Jeff Korn

88 Turbo Coupe: Intake and exhaust mods, T3 turbo at 24 psi, forced air IC, water injection, BPV, Ranger cam, subframes, etc., etc.
86 Tbird 5.0 (original owner): intake, exhaust, valvetrain mods, 100 HP N2O, ignition, gears, suspension, etc., etc.
05 Taurus SEL Duratec daily driver
04 Taurus Duratec (wifes car)
02 Pontiac Grand Prix GT
95 Taurus GL Vulcan winter beater
67 Honda 450 Super Sport - completely customized
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Hwyman Offline
Member
#8
Pete. can you send my that diagram. I'm interested in it also
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Pete D Offline
Administrator
#9
Quote:Pete. can you send my that diagram. I'm interested in it also
Not with out an email addy I can't
Pete Dunham


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Matt S Offline
Posting Freak
#10
So if I can take a small 12v lightbulb and attach it to the battery (+ and -) and it lights up without blowing the bulb or shorting anything...why can't I do the same for the 12v across the 2 fan wires?

In the IRCM, is there a separate power feed wire that activates a relay that I could tap into (the 20mA or whatever current that activates the relay to provide juice)?
Sold it Sad*
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