Ignition/fan wiring question

[MaineShark]

I need a source of switched power for my fans.

Specifically, I'd like to tap the IGN3 wire, if possible (from my reading of the wiring diagram, that wire is connected when the switch is in "run," but not when the switch is in "start," which is what I want).

So, I know what I want, electrically, but I'm not sure where that wire is, physically, and where might be a convenient spot to tap it.

Thoughts?

Joe

 

[JohnZ]

If your fans are wired to your ignition circuit, they'll fry the ignition switch - way too much current draw for the switch to handle. Use a relay with its energizing coil wired to the ignition, and a separate power feed, switched by the relay, direct from the battery to the fans.

 

[MaineShark]

I have a pair of relays (Delco P/N 14089936 - C4 fan relay) to run the two fans, but I need switched power to hook to one side of their coils, so they only operate when the ignition is on. I'd like to tap the IGN3 circuit, since it will shut them down when the starter is cranking (reduced stress on the electrical system).

Looking at the diagram, I think the IGN3 circuit runs only between the ignition switch and the fuse block. It goes to a terminal marked "WDO", and from there to the A/C use. I looked at the fuse block, and there's a small silver box between the two - I assume it's a fusible link of some sort. From the A/C fuse, power goes to the climate control switch.

In any case, I think the only place I'll be able to tap this cirucit is the ignition switch, itself. Unless anyone has any better ideas?

If I have to catch it there, what's the best way to get through the firewall?

Joe

 

[biltogo]

Wouldn't a lead from the ACC terminal on the fuse block work? If I remember right, that's the lead to the relay I used with my Spal fans.

Does this help?
http://www.spal-usa.com/pdfs/Fan Relay Harness.qxd.pdf

 

[clar2001]

I hooked my fans relay the ing. one to the fuze block. I just used a meter to test a lead that was only powered when the key was on works great ,the main power wires from the fans I hooked to the 6gage red wire coming out of the fire wall,this way I diden't half to run all the way to the battery .The starter wire witch some people here recomended diden't work out pulled to many amps that way,the thermostat sensor is in the intake manifold instructions said cylender head but it works even beter this way.both fans are wired togeather ,so when they first come on for a 1/2 second my battery/amp guage goes to -40 then right back works great .

It was 90 degress today and I coulden't get over 185 degress in traffic ..............she runs cool

 

[clar2001]

Here is a pic of my fans not that great of a pic

 

[geekinavette]

Joe, does your car have power windows? The silver box you described is a circuit breaker and are usually used for power windows/locks, and I believe that's what the WDO stand for..."window". I suppose they used circuit breakers (as opposed to fuses) since if you hold the window switch (for example) after the window has reached its travel limit the motor current will increase dramatically...blowing a fuse every time.

The 40A draw when the fans engage sounds about right, they're usually rated right around 20A each.

Bill

 

[MaineShark]

Wouldn't a lead from the ACC terminal on the fuse block work? If I remember right, that's the lead to the relay I used with my Spal fans.

I want the IGN3 circuit, since it is disabled when the starter is running. That will help reduce the strain on the ignition system.

clar2001: I'm not sure about the differences between '75 and '79, but my car doesn't have any 6-ga wire anywhere, that I'm aware of. The largest wire is 12-ga, other than the 2-ga battery wire (which connects directly to the starter terminal). The only large wires other than that, are the two 10-ga wires that I just ran - one from the alternator to the starter terminal, and another from the starter terminal to my new fuse block where the fans and electric headlights will get power.

Bill: Yeah, that's the window circuit. The power windows and A/C connection are on the IGN3 circuit so that they won't draw power at the same time as the starter, which is what I want the fans to do.

Are you sure that's a breaker? It's pretty small, compared to the other circuit breakers. That's why I thought it might be a fusible link.

Is the best way to access that circuit to pull the fuse panel and get at the back? I really dislike wire splices...

Joe

 

[clar2001]

well it sounds like your doing every thing properly, the red wire I refure to comes out of the fire wall in two places right next too each other by the wireing harrness then joins togeather and runs to the ac as a single wire stranded copper, the actual wire going to the ac is smaller than were it hooks too the harrness, this was the only heavy gage wire under the hood other than the battery post on the starter. Each fan has its own 30amp fuze right off the wireing harrness.
I did up grade my alternator to a 100amp to handle the fans and my stero amps witch it does no problem ,sounds as if you may of done the same thing since you ran new wires for your alt.

P.S I do want to switch to Ing.3 also so when you start it hot it doesen't pull to hard on the system works fine now but that would be a great improvment.

 

[clar2001]

ok here is a pic notice the double red wire on the right thats from the wireing harness the red wires on the left are my fans tied togeather with the blue cap. I removed my wiper washer to be able to do this it hasen't been reinstalled yeat.

 

[MaineShark]

I did up grade my alternator to a 100amp to handle the fans and my stero amps witch it does no problem ,sounds as if you may of done the same thing since you ran new wires for your alt.

I'm going to pick up a new alternator either tomorrow or Tuesday

I'll let you know what I find when I try to get at the IGN3 circuit. I think I'm going to need to unhook the fuse panel and pull it forward (I'm hoping there's enough slack in the wires), then attach a lead to the back. Hopefully I will be working on that tomorrow afternoon/evening.

P.S., I think you have a 12-ga wire in that picture, not a 6-ga. 6-ga wire would be about twice as thick as 12-ga, and at least half the thickness of the battery cables. Big wire...

I like your wiring, though - I didn't have the patience to pull my wiper motor when I ran the wire over to the alternator, so the wire just goes in front of it (but behind the wiring connections to the wiper, so hopefully it won't stick out like a sore thumb. My fan wiring is all on the passenger-side inner fender (next to the A/C compressor), so
I didn't have to run a long wire for it.

Joe

 

[clar2001]

All I know about the gauge is I bought red 6gauge wire a home depot to do this job and it was the same size as under the hood maby dc voltate auto guages are different .
I got my alternator from summit for $124 100amp after shopping around that was a pretty good price for a polished one.Bolted right in , I was suprised to see a tag on it that said at 800rpm would produce 85amps and at 2000rpm was 115amps. now my windows even go up faster .
Your going to love the fans they do a great job has a little bit of noise but kind of a unique sound to here fans like that on a older car, the alt also has a little wine to it not enought to bother you just a different sound than stock....

 

[MaineShark]

All I know about the gauge is I bought red 6gauge wire a home depot to do this job and it was the same size as under the hood maby dc voltate auto guages are different .

Probably different insulation thickness...

I got my alternator from summit for $124 100amp after shopping around that was a pretty good price for a polished one.Bolted right in , I was suprised to see a tag on it that said at 800rpm would produce 85amps and at 2000rpm was 115amps. now my windows even go up faster .

I just bought and installed my new alternator, today. $95 locally for a Delco 100-amp unit that bolts right in. Only change that was necessary, was to get a new plug for the two wires that attach to the side (one triggers the idiot light in the dash, and I believe that the other senses the battery voltage to turn the alternator's charging circuit on and off to maintain the correct charge). The original plug was in bad shape, anyway, so I didn't feel bad about cutting it off and replacing it.

Your going to love the fans they do a great job has a little bit of noise but kind of a unique sound to here fans like that on a older car, the alt also has a little wine to it not enought to bother you just a different sound than stock....

Yeah, it's getting close. I've figured out the mounting brackets (which was the last big hurdle), and I just need to fabricate them now. I've wired each fan with a three-position (SPDT for you electrical types) switch, so I can select each one to be triggered by the ignition, or by the temp switch, or to stay off. That will allow me to bypass the temp switch easily if it ever fails, as well as having it set up so that one runs automatically, and the other comes on with temperature, and will also allow me to switch them both off for short periods of time, if I'm trying to listen for a noise and want to cut off the fan noise.

Joe

 

[Culprit]

Joe,

Are you going to mount the SPDT switches under the hood, or in the cab somewhere, ie under the dash?

Culprit

 

[MaineShark]

They'll be mounted next to the relays, under the hood. It's not really anything I plan on playing with a lot. I just figured I would put them in while I was at it, since they aren't much trouble.

Does anyone have any ideas on this IGN3 circuit? I've tried getting the fuse panel out, but no joy. There were two bolts that I could see, and I removed both, but it still won't pull away.

Is there a trick to getting the fuse panel out? If it's too much trouble, is there an easy (reasonably easy, at least) way to access the ignition switch, directly? I've heard that I need to remove the whole steering column to do it...

Or, alternately, is there any way to access that circuit from the front of the fuse panel, before the fusible link/circuit breaker? I'm guessing I'd need some sort of plug with the same shape as that device's connection, and then a socket for it, so that I could "piggyback" the tap into the hot side...

Thoughts?

Joe