My newly installed electric fan controller needs switched twelve volts. The instructions call for a voltage that doesn't waver or have too much noise or it could cause damage to the controller.

Any suggestions on a source under the hood which would be good for this?

The only ones I can think of off hand are the coil and the choke but both of these might waver or be noisy depending on the load.

I'm guessing here but would it be better to run a line from the switched radio power or right from the ignition switch inside the cab?

Thanks.

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Sweet Emotion

If this is to support the whole electrical load of the fan, it needs to be a LOT higher capacity than you can get off the radio line! Suggest you run a new fused power line to the alternator output stud, which is electrically common with the battery positive terminal, and splice a relay into this new line, which is triggered by any ol' key-switched 12v circuit (radio would be fine for this, since relays take almost no current at all). You could even get a fancy relay with a time delay-on-off (Bosch makes one) so the fan would run for a minute or so after engine shutdown to help cool the engine bay and prevent gasoline evaporation.

If there's electrical noise, it's going to be present clear across the whole system (though bad grounds will increase the effective "noise" locally). If your voltage is flickery, now's the time to fix it.

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Too many people who were born on third base actually believe they've hit a triple.

No it's not the fan primary power. It's a low current control line to the controller brain. The Hayden controller also has a 40 amp relay built in which is controlled by the controller via the coolant sensor and switched power. The source for the fan comes from the battery plus side via a 10 or 12 gauge wire. This control line I'm speaking of is a 22 gauge wire. BTW I currently have this switched power tied to permanent 12 volts and the fans stay on too long after power down so I want to run this control line to ignition switched power.

I like the delayed relay idea as well. Do you have a part number? I did some searching and was only able to find soem with very short delays. A minute or two would be ideal but in the current configuration the fans stay on for 10 to 20 minutes until the top tank cools enough to shut the fans down. This is too long for my tastes.

Your point about noise being throughout the system is well taken. I was just wondering if tapping off the coil or the choke might not be ideal for this Hayden controller.

Thanks.

One other thing that's stumping my thinking here is I am controlling the fans based on the temperature of the coolant in the top tank. I don't hav a convenient port in the bottom of the tank but the top seems like the wrong place as it is the inlet to the radiator. I suppose I could put an adapter on the drain plug and install it in the bottom. I'm wondering how much the temperature drops from the top of the radiator to the bottom of the radiator? Not sure this would help the fan on time after shut down but it might require less fan on time during operation. There is an adjustment on the contoller for 160 to 220F I have it almost all the way up right now.

The other thing that I'm having a hard time getting my mind around it there are really two temperature control loops. The block/thermostat loop and the radiator fan loop. I'm just not sure what the system can tollerate under harsh conditions in terms of the collant temperature as it enters the water pump. Any help here would be appreciated.

BTW I have not run this on the road during the day yet until I get these issues resolved, but at night I get good performance. At least the temperature gauge remains fairly constant although sitting in line at a burger joint it started to go up a little but I think this is normal. Fans were on of course during the 10 minutes or so I was in line. I guess what I'm saying is I'm not sure my fans have enough capacity.

Also what should the alternator gauge do at idle? Mine wavers at idle below the charge line bobbing around. Above idle it's at about 1 oclock solid. It goes up a little when the fans come on. I have good wiring and rebuilt alternator. I completely repaired all the under dash and under hood harnessing this past year when we had the car disassembled so I think my wiring is in near perfect condition. Including the amp meter wiring which I know is critical.

Thanks

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Sweet Emotion

Oh, OK. Anything'll work, then. Your radio idea is a fine one.
Gotchya. Which Hayden controller did you get? They make some very fancy ones.
Yes, I have the P/N for the Bosch adjustable-delay relay, at the office. When I'm there next, I'll post the number for you in this thread.
Yep, definitely too long.
It might seem so, but the top of the system is where most factory systems sense coolant temperature. All the late-model Mopars, for instance, have the temp sensor in the head or thermostat housing, up at the top of the system. And gauge senders have always been up top, too. It doesn't stand to common sense, but that's how it works, so enjoy not having to reëngineer things and leave it be.
There is nothing to be concerned about here -- you'll be boiling and steaming and frothing and knocking long before the water pump's thermal resistance is taxed.
Sounds as if they might not -- they shouldn't be on for 10 minutes at a time, and your temp gauge shouldn't rise when sitting at an idle.


With most pre-'88 Mopar systems, with electrical accessories switched on, it'll dip below the centre and point partway towards "D" at idle.
Not good; figure out the source of the slow/poor voltage regulation and clean it up. First thing to try is adding a ground loop (wire from the "GRD" hole on the back of the alternator housing to the voltage regulator base, and from the voltage regulator base to the battery negative terminal). Next suspect is alternator brushes or other internal parts.
"Rebuilt" means a competent auto electrican disassembled and rebuilt it, or "rebuilt" means a piece of junk off the parts store shelf?

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Too many people who were born on third base actually believe they've hit a triple.

Well wait a minute now, is this not so that the gauge will rise rapidly when the water level drops below the level of the sensor? I always assumed that to be the reason.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Nope, quite not. If the water level drops below the sensor, the temp gauge WILL NOT indicate an overheat condition, because the air above the water will never attain a temperature high enough to push the gauge needle into the danger zone. With a coolant level below the temp sender, the engine will be cooking itself to death and you'll never know it by looking at the temp gauge.

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Too many people who were born on third base actually believe they've hit a triple.

The Hayden controller is kit 3651.

Regarding the voltage bobbing around on idle, is it possible the voltage regulator is bad?

That is one thing on this car I have never replaced.

Is there a test I could do with a scope or voltmeter to test the system?

Also what idle speed if any would cause symptoms like this?

And I am wondering if the voltage is wavering could this also be the cause of intermittent engine stalls when I approach a stop sign?

Thanks for the help.

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Sweet Emotion

Really? Weird. I have seen machines that have run out of antifreeze and the gauge was pegged. How does a coolant level sensor work, anyway? I have always wondered about that...

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Same way most temp sensors work: a variable resistance element whose resistance changes with temperature.

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Too many people who were born on third base actually believe they've hit a triple.

Certainly!
Well, you can full-field the alternator and see if the wavering voltage steadies up. Can't recall if you're running a '60-'69 or '70-up charging system. Think it's the latter, though, so I'll give instructions for that. Warm up the engine so it's on hot (slow) idle. Your alternator has two field wires on the back of it. Disconnect them both. Connect a test lead from one (either) of the alternator's field terminals to a good ground. Connect another test lead from the alternator's other field terminal to the alternator's large B+ (output) stud. Start the engine and let it idle under the conditions that normally cause the wavering voltage. Observe the ammeter. If the needle still wavers, there's a fault in your alternator.

If the needle no longer wavers and you have already tried running a ground loop as described above, your voltage regulator is faulty.

Don't increase engine speed above approx 1000 rpm (and then only very briefly and only if necessary) while performing this test, for the alternator is operating without regulation and will crank out lotsa volts if you let it.
The line voltage should be smooth and steady at all engine speeds.
Not terribly likely, no.

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Too many people who were born on third base actually believe they've hit a triple.

OK, I'm (still) at the office. Bosch makes two different time delay relays: One has a release delay adjustable from 3 to 30 seconds (not really long enough, I don't think, but your opinion may differ) P/N 0335330801, and one has a fixed release delay of 90 seconds (just about right, IMO) P/N 0335330802. I've got one of each coming to the US in an air parcel from Germany that should be here in 21 days or so. The terminal configuration of the 90-second relay is a little hard to figure out, but it comes packaged with circuit diagrams. It is configured so that you can wire it up to cause the fan to run for 90 seconds after engine shutdown *if* it is running at the moment you shut off the key. It also comes with a relay bracket/terminal block and appropriate terminals.

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Too many people who were born on third base actually believe they've hit a triple.

Whoops, sorry 'bout that, I misread your question.

Coolant level sensors (windshield washer level sensors, too) usually work on a simple circuit-completion basis: two pole pieces protruding into the conductive liquid (coolant or screenwasher solvent). As long as they're submerged, the circuit is complete and the light stays off (by one or another means of reverse logic...a NC relay or a loopback circuit). When the pole pieces are no longer submerged, the circuit is broken and the light turns on.

Sometimes, especially when the level of a nonconductive fluid must be sensed, a float switch is used instead, just like the kind that tells your kitchen dishwasher when to stop admitting water.

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Too many people who were born on third base actually believe they've hit a triple.

Do they make any with a half second delay for the ignition circuit? The ones Ive been getting from electro.sonic are solid state, but theyre expensive.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.

Half-second delay...?

I give up: What for?

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Too many people who were born on third base actually believe they've hit a triple.

This will delay power to the ign. coil for a half-second to give the starter pinion time to fully engage the ring gear. This will help prevent kickback against the starter that can cause a broken nosecone or chipped teeth.

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I've been calling it as i see it for my entire life and that's not about to change. Take it or leave it.