wiring in electric fans

what wire can i use underhood to hook up the wire from the fans so i have power when i turn on the key Thanks

The blue wire at the ballast resistor is keyed power but you can only use that to energize a high-current relay to carry the load of the fans.

you'll need to know what the fans draw current wise for two reasons, 1. make sure your charging sytem can handles the addedd load and 2 so yo know what size fuse and relay is needed

A diagram I made quite ago for a full dual fan setup, including the option for the extra cooling when A/C is on. Using temp switches.

Nice diagram nacho
He still needs to check his current draw and charging capacity

I installed one large aftermarket electric fan on a drag only car years ago and found that it would draw 70+ amps on startup initially
To much amp draw can melt overloaded, to small, wires real quickly

A little more info on how you have or plan to have this fan wired would be helpful. A relay switch and possibly a breaker switch is highly recommended to help isolate the load on your electrical / charging system.

The relay has four wires: 1) 12v constant from battery 2) 12v remote-on (powered by key switch) 3) Ground 4) Output to Fan. If you run a simple breaker, it goes inline on the 12v constant wire from the battery to the relay.

The 12v remote-on source you're looking for can be found in various places. Most fuse panels have extra tabs on a few of the 12v sources that only have power when the key is in the run position. You can simply run a wire from one of these 12v sources to your relay switch. Since this wire only triggers the relay switch "on" they draw very very little current and don't need to be a heavy gauge wire.

Fans can draw a lot of current. It's important that you're running a relay meant to handle the load of your fan. Additionally, an electric fan may require an alternator that has an output greater than stock to keep your battery charged.

-Dan

Many good replies already.

To get the full benefit of an electric fan addition, and most $ return on investment from fuel economy, there should be a switch to turn the electric fan off at highway cruise to lessen un-needed air coming in through the grille and going out the bottom of the engine compartment, then flowing against the rough under carriage.

With the fan turned off the engine coolant temperature should be allowed to rise to at least the 220 to 240 degree F level which also improves part throttle engine efficiency, and heats the air up flowing through the throttle so the throttle blades will open up, improving manifold absolute pressure, and lessening the amount of ‘negative work’ the engine produces dragging pistons down against a vacuum on the intake stroke.

Either a knowledgable human driver, or a well written microprocessor program, should decide when to turn this switch on/off.

On top of this recent Ram trucks have grille shutters to lower harmful airflow at part throttle highway cruise.

I use a pulse width controler from Auto cool guy, works awesome, CLICK HERE

That is why the load for these should never be off the alternator stud. Worse on older cars with inductive ammeters and failure prone bulkhead connectors. Alternator should be wired with protection direct to the battery or a buss connector. All loads should be off that point and correctly set up with relays and fuses.

I have one of Autocoolguy's controllers on my 451 Dart, with Ford Contour electric fans. Pricey but works great.

With ammeter, all loads must be sourced from alt side of the charging network, never from batt

You are so wrong. Anyone that wires these old cars off the alternator stud with old wiring and connections is a hack.

I used this on my car, thought it was a good price and saved some time.

https://leashelectronics.com/products/dual-70-amp-relay-board

I have dual electric fans. One is wired in and thermostatically controlled to come on automatically through the Racepak. The second one is wired into my overhead switch panel mounted to the cage halo bar.

Two conditions to get it right.

Once you add accesories as an upgrade on your car, i.e. electric fans, the alternator must be upgraded accordingly. Stock configuration for a correct ammeter reading is everything must be sourced from alt side. You need just to check a factory diagram to prove this is a must.

So the conditions if keeping ammeter on car to be correctly sourced are:

-Everything must be sourced from alt side
-alt must be upgraded accordingly to the new accesories to keep the right reading and the loads going throught the correct side.

Several reasons why wiring on Mopars are a weak spot and this is on 70% of times owners/mechanics fault by the unkownledgement of how the system works.

The alt provides what the car and its accesories requires to work and tries to keep the batt fully charged, nothing more, but less is not capable.

If you source anything on batt side, more load will go through the stock wiring, bulkhead, ammeter etc… like if the batt will never get fully charged. So if you source, on this case, electric fans correctly on alt stud, the load the alt will supply to source them, WON’T EVER RUN through the stock wiring but straight from alt to the fans relay setup. BUT if you source them on batt side the required load to feed them will be stressing unnecessarily throught the stock system and amm will be constantly on CHARGE side.

Which is true, bulkhead is a weak spot, and stock alts are tipically unable to keep the batt charged at iddle, hence why when revving up the engine, the ammeter senses CHARGE. This is increased with loads hooked up on batt side as mentioned.

The only moments weakness of the stock system becomes critical sourcing CORRECTLY the added accesories on alt side is when the alt is unable to source most of the required loads (or engine is off, so does the alt ) and battery becomes on the constant main source. This is the moment when the ammeter becomes on a dancing gauge going back and forward along with engine revs. The more load going back and forth along the charging system, the more heat is able to get and this is the moment becomes on a dangerous stage.

Since the beginning EVERYONE began to source added accesories on batt side. This along with the weak bulkhead spot (which is true) and the unneficient stock alts at iddle is what got our Mopars burning wiring along the years. Add to this, ppl “upgrading” batteries with more reserve capacity to hold added accesories, which it took MORE time to keep them charged by the uneficient stock alts… so more stress to the system.

So in conclusion:

Hook up the fans on alt stud and upgrade the alternator are the correct way to proceed to keep safe the wiring and ammeter and EVEN THE BULKHEAD conector, because bulkhead won’t get ever this load correctly soorcing the fans. But is true some easy wiring mods are advice just in case, like save the bulkhead connections with some paths and wiring upgrades… which has been already shown and discussed in the past on several threads when talking about alt upgrades and those who thinks the ammeter bypass ( or the jumpong wire between alt and batt ) is the solution. No need to jump out batt with alt, which bypasses the amm reading. And with the correct procedures, the ammeter will be still safe and reading strong and correctly

Being there done that, on a driver ( A REAL DRIVER ) 74 Mopar on a heavy transit city.

Which is also true is when proceeding with any add on or upgrade, the related system must be correctly checked to be sure if will survive to the new part or upgrade.

Wrong. You show me one car or truck that the loads are sourced off the alternator stud. Show me do not avoid this direct question with mambo jambo. Next tell me with your VooDoo alternator stud taking all the add on load what happens when the alternator quits charging??? Where does that load no go? Answer that. There are right ways to do this and yours is not it.

ALL CARS ( not just Mopars ) with ammeters are sourced from the alt side of the ammeter... no matter where... if straight from the alt stud, the ammeter stud or an intermediate splice... as far the loads are taken from the alt side of the ammeter.




diff stuff you tipically never see anything hooked up to the alt stud because splices are down the tape harness, but for new adds without untape the harnes, the two points to source correctly new accs are amm stud or alt stud

You never answered all the questions.

unfortunatelly the thread where I explain all details about upgrades of the charging system got missed the attachments due a forum software upgrade. Will work on recover those, but for a while:

https://www.forbbodiesonly.com/moparforum/threads/poll-about-ammeter-reading.198930/page-3 ( linking to the 3rd page whre I begin to put pics about how the charging system works )

http://www.heritech.org/cuda/Charge.html

questions are answered on dozens of threads where this has been discussed. BUT just begin with those. I can post many but don't wnat to highjack the thread (more).

BTW, diagrams are mine... which I made back in 2007... weird you haven't seen these also on Moparts.

all answers you posted are on diagrams and their explanations...

The main issue here is whether or not the car has an ammeter. With an ammeter, the goal is to avoid having large amp loads flow through the ammeter. Hooking large loads to the stud is one way but, if the ammeter is left in place, a large wire from the stud directly to the battery will bypass the ammeter and carry most of the load...a voltmeter will be needed to monitor the system voltage.

IOW, there is no right/wrong way, it's simply a matter of preference.




Since the stud is hooked directly to the battery (Nacho's first diagram fails to show that), the load is handled by the battery...as long as the wire is sufficient in size, no problem...the load is handled by the battery as a "total loss" system.

I didn't fail on show the alt stud hooked directly to the batt... simply because is not... they are linked sure, but running throught the bulkhead, amm, starter relay stud.

i simply did show how how are actually wired every car with full load ammeters (shunted systems are a diff story, but not so different)... Mopars, Phords... whichever other brand. And ALL cars with ammeters get their devices sourced on alt side of the ammeter... no matter if an intermediate splice, ammeter stud, alts tud or some juntion point... Fuse box is also sourced from this side, being spliced into the amm-alt line. Yes, it says BATT, but just as a reference for a constant power coming from the power sources... alts if cengine is running or batt if engine is off.... or batt-alt combination depending on alt capacity.

JUST the starter motor is not sourced from alt side, of course. Sometimes some accesories which just work at certain points being not a constant power source suckers, like power windows could be also on batt side not on alt side

Thanks John. At least you see it. This nonsense of wiring high amperage devices to an alternator stud without having the rest of the system able to carry all the possible loads is asinine. Its also senseless as there are better ways to CORRECTLY wire an alternator for loads. When using high out put alternators the alternator should be CORRECTLY wire sized and CORRECTLY wired direct to a distribution block with protection on that circuit. The distribution block would be linked direct to the battery. All circuits then would be CORRECTLY fused with relays as needed out of the distribution block.

If keeping ammeter and planning to keeping reading correctly, you SHOULDN’T wire anything into the batt side.

I never said wiring doesn’t need to be upgraded or at least adviced, but there is a just one correct way to make it keeping the ammeter working correctly and is not linking the batt and alt with a jumper wire

BTW, you can install a 500 amps alt, but if the car just sucks 45, the amp will provide just that. Amperage is demanded by the accesories, not simply put out by the alt by its own.

You feed with the same battery the map light with a 18 gauge wire than the starter motor with a 2 or 4 gauge wire. The wiring must be matched with the device to be sourced, not necesarilly with the source capacity

Well that's stupid. It sure wont work as designed that way. Might as well tie the wires together and run a voltmeter.

Some C-bodies of the seventies had such a distribution block in the form of an insulated stud that mounted on the inner fender panel near the battery...when junk yard hunting in the old days I used to snatch these up for use on my rods. Hi-amp loads like power windows/seats and tailgates drew their power from this stud.

Nowadays I use this:

https://www.summitracing.com/parts/rra-fs46540

some late 90's, early 2000's minivans have a nice, compact distribution block with fuses and relays, that measures 3" wide, 8" long, and 3" tall.
these can be easily wired and hidden if necessary, in our early rides.

Just for interest of anyone interested… and just testifying about a satisfied “customer” (if my personal experience I share, made on my own car is still not enough) with some suggestions I made privately for it:

https://www.forbbodiesonly.com/mopa...e-to-a-volt-meter.240840/#post-912248339

There is about half of dozen of ways to make it quite fine… some with more intervention of the wiring (like the one posted), some other with lighter mods (like the one I made on my car). But allways splicing out correctly the power source ON A HIGHER POWER PLANT CAPACITY unit ( aka, alternator ) able to source the new adds at the lower alt speed as posible and still with the stock “tiny” ammeter gauge on line.

On the previous reply to the one I linked (#12), a member is quoting the thread I composed, BUT is still with the attachments missed. As mentioned previously, hoping will be recovered.

Yes, on B bodies with those same options, these accesories were sourced straight from amm stud on batt side (which is the same than using a junction close to the battery like the one you described ) instead the alt side like regularly should be because these are not constant power suckers, just ocassional. Leaving these on batt side, the ammeter will register the small amount of the charge load the battery lost when working althought for more time depending on alt speed, but will be safe from the load peak they suck on the operation moment. Just like the starter motor, which its operational load is not registered on amm, but the load lost after crank up getting back to the batt (charge) slowly and on lower rates than what was used to work once alt is able to do it when spinning.

I think I mentiond this on a previous reply… not extensively detailed like I did now.

Just more jiberish on a hack job.

Wiring an electric fan on a OEM charge path muscle era mopar is an exercise in select the lesser of the evils you wish to confront. There is no perfect spot to pull power in engine running and engine off modes.

The only gibberish in this conversation is coming from you.

Agreed, however also depending on how you wire the setup for the best. If you set it to be turned off with ign key or automatically with a temp sensor switch no matter the ign key.

On the second case the fan should turn off in a minute or so. And if the paths are upgraded you shouldn’t get any problem.

But the ammeter can be still on the line. The fan won’t suck more than the ammeter is able tiohandle, being the only device still sucking once you parked your car.

Assuming also of course, the Charging system has been checked for weak spots before any alt upgrade or accesories added. You can’t expect to get a perfect system on a non checked 40 years car when adding stuff. Call it electrical or mechanical parts, but tipically electric parts use to be underestimated, then failures appear and begin to blame everything but the real cause.

Is like when you select a camshaft going for a power upgrade and CR along with TC being or not considered, so you can fall into an “overcamed” car. The difference is a camshaft won’t get in fire your car, like an underestimated electric system for check and mantenience could be able to.

One crucial point to keep in mind when wiring add-on electric fans..
Since they draw large amounts of current (>30 amps) do NOT use the bulkhead connectors, as it exceeds their handling capabilty..

Just my $0.02....

Yes, but STILL if bulkhead terminals are kept as the main path there is allmost nothing to worry if wired into the CORRECT alt output rate. Just when engine is off, and when this happen as mentioned if you set them up to be on JUST with ign switch on… and if to be automatically off with temo sensor switch, fans will be working for a minute or even less. Still on this stage, bulkhead will hold it nicelly.

Take in mind, RELAYS are made with prongs allmost just like the packard terminals, and they handle the load! But sure, when installing those, they are fresh brass… but bulkhead terminals… not. Check and MANTENIENCE is the key

Over the years, we have rebuilt multiple Mopars and wiring systems which were modified by less experienced guys for electric fans...
Bulkhead connectors and associated OE wires were not designed to handle the high current. Since we have designed & built multiple vehicles for CES and SEMA shows we do know a little bit about this..

Just my $0.02...

The point everybody is trying to make is DON'T RUN HIGH-AMP LOADS THROUGH THE BULKHEAD CONNECTORS AND AMMETER. Whether it's wiring directly to the alternator stud or a parallel wire is a simple matter of preference. No right/wrong here.

small, cheap,
digital readout amp meter
with remote placement hall effect current sensing loop

https://www.amazon.com/bayite-Digital-Current-Voltage-Transformer/dp/B01DDQM6Z4

I would guess there are other designs,
and maybe even past OEM car and truck dashboard gauges to be found in salvage yards?

Yes, there is a wrong way to make it if you don’t understand how it works.

Attaching to the alt stud WITH THE CORRECT alternator, won’t get the bulkhead or ammeter loads going through, except with engine off and if fans are still running.

ONCE AGAIN, WITH THE CORRECT ALTERNATOR OUTPUT RATE.

Anyway, get the bulkhead path bypassed it will get a better charging system STILL with the ammeter in line, as far ammeter is also in good conditions… checked/serviced after all these years of use and abuse.

STILL WITH A 500 AMPS ALTERNATOR.

(Amps are not pushed in by the power source but sucked out by the accesories. Power source just need to be able to provide them anytime)

Sure, it happens… making it wrong sure takes to that scenario. And without considering the correct loads handled on every spot at certain stages.

I guess it got a 8 gauge wire or so to source it? LOL.

Most fans are wired into 14-16 gauge wire rate. Sure the start up instant would require thicker wire if the load for it was constant, but the start up high peaks are not larger than 1/4 of second or so, then the decay is abrupt once the fan stopped inertia is beaten

Correct fan wiring.

You are not understanding.

NOT WITH AMMETER EQUIPPED CARS,

I fully understand. I would bypass the ammeter and install a voltmeter. I would also install a fused larger gauge wire at the alternator to either a buss terminal, relay stud or battery, large enough to support the alternators maximum output.

Thats a DIFFERENT STUFF. All my explanation is based on cars still with ammeters in working order and also explaining how ammeter can be kept in place still with upgrades and safe.

The installation you posted is exactly the kind one which, on stock setup, acelerated the bulkhead burning process along the years and get ammeters out of their limits, being constantly stressed.

Now, bypassing ammeter and bulkhead at the same time with the tipical batt/alt jumper wire is, as told by John is a matter of prefferences, but even this must be made on the right way.

What happens when you are 50 miles from home and the alternator quits. Where does the load go then?

It comes from batt to feed fan, ammeter will show discharge. Sure, bulkhead and ammeter will get the fan loads.

Are we assuming the fan is replacing the stock fan clutch? Or being added to reinforce it?

But if alt quits the right thing is take the car appart and wait for tow, just like if brakes fail or Ign module.

In any case, that’s the exception, not the rule. If we think on every “WHAT IF” posible then don’t try to live.

You can also disconect the fan, and drive back home. Just 50 miles.

Also, if you think on every “what if” well, the same than get small spare parts on trunk, a piece of wire to jump out batt and alt and bypass the amm and bulkhead.

If you are driving at night, lights also will be affected, then the ammeter too.

Alt can fail also with belt broken… which is maybe easier than an alt fail itself.

What about if fan fails?

P.S.:
That’s why I’m fan of the stock fan clutch.

How many modern cars have an engine-driven fan?

It should not be forgotten that the silicone fluid in viscous or lock up fan clutches can be changed
so that the unlocked fan rpm can be varied - less to save horsepower or improve fuel economy,
but also more viscous to move more air.

Realize that fan designs done by CAD have greatly improved in the past 15 years - quieter and use less power to move more air.

Today’s best fans “look like mean Klingon weapons”
with sharp points, edges and creases that both stiffen and improve aero
but the blade positions around the hub are not always symmetrically arranged

If you are a bit shocked,
and think:
“I would really hate to stick my hand down into that”
it is probably an improved design.

John, how many cars still have carburetors? How many got ammeters? How many have a single coil or even a distributor? That premise doesn’t have sense my friend about the cars we are talking and working.

But it does reply to the question "what about if the fan fails". The same as if your fan belt breaks, s**t happens and that's no reason to reject a modern upgrade.

Well, yes… but at the end is cheaper and easier to replace the belt than the fan LOL. And you can get a spare on trunk

Yes, because OEM electric fans have such a failure rate that it is an issue

If you use a non OEM style fan, well you take your chances.

I put an electric fan on my 51 Plymouth. Several reasons why. I watched an engine masters dyno test where the fixed style fan my 51 had used approximately 30 hp to run, on a 97 hp (when new, lol) engine. So that was a cheap and easy 30+% increase in HP to the wheel. Not to mention it's quieter and fuel economy improved without that fixed fan running all the time.

If you're driving down the road and your fan belt breaks it usually drives something else as well. So not only have you lost the cooling effect of the fan but you're no longer pumping coolant through the motor. And quite likely you've lost power from the alternator as well.

On the other hand, if your electric fan bites the bullet you'll still have coolant flow, power, etc. and the airflow through the rad just might be sufficient enough for you to limp home.

Guys, I just said and fan of the stock fan clutch, not saying anything againts the electric fans LOL.

About what I’m not agree is getting the power to the fans from battery without take in mind you have an ammeter, which is a wrong procedement. This is the deal on the thread. Aside the alternator must be upgraded accordingly for it/them.