240Z altenator with twin 12" thermo fans

[d3c0y]

Can i run two 12" thermos on stock 240Z altenator?

 

They draw 6.7amps each and the car doesnt have a stereo or internal fan.

[sexual_sushi]

I've got two 10" thermo fans, a head unit (no amp) and h4 headlight upgrade running on my 240z (with l26) and it is fine. Note sure what amp the alternator is, although it is definitely an externally regulated one.

[PZG302]

Standard 240 alternator is rated at 35amp if memory serves me correct.

 

So all up you should be OK, depending on what other accessories you are running at the time, eg headlights & wipers.

[d3c0y]

Yeah still packing sealed beams, only other thing i run is a crane CDI. I'll give it a go!

[twosixty]

It might seem okay looking at the numbers, but if you do go ahead with it I would suggest budgeting for an alternator with a larger output. It is just a matter of time before a not so new battery and alternator, some short trips in the zed and 40 year old wiring losses catch up to you.

 

On a related note, what thermos are you going to fit?

[matty260z]

That should be fine. I imagine your running the fans on a thermo switch? Let me know if your looking at upgrading your alternator or cooling system, you don't want to pay full retail price

[Zedman240®]

240Z standard system should handle that ok, you might look at a 11 plate or 13 plate battery for that extra back up, all the electrics run off the battery, the alternator tops it up.

 

It's the other way around; car runs off the alternator and battery is a backup source and really only there for starting.. 

[luvemfast]

It's the other way around; car runs off the alternator and battery is a backup source and really only there for starting.. 

+1

Start the car and remove the battery, point proven

[zedrally]

You might to to consider the fact that the fans will not be used when "flying" down the road, only when stationary!

[luvemfast]

Think that would say more about the condition and state of the individual's car (alternator) as a whole.

 

This is a direct quote from your link Salty

A car alternator is responsible for powering a car's accessories--radio, lights, horn--during normal engine operation. The car battery supplies the initial charge that allows the car to be started, and then the alternator takes over the job of supplying a constant electrical feed. In addition, the alternator is responsible for recharging the battery after the battery loses some of its strength from starting the car.

Every car I've ever owned runs without the battery

[Ben]

Fit a wide-stator Bosch alt. from a 910 Bluebird  (series 1 auto I believe). I've got one of these modified to 90+Amps in my 240Z. I wouldn't rely on the original spec. parts with the external reg to keep 2x thermo fans happy - on a hot day in traffic (or at night) I think you'd flatten the battery.

[Six_Shooter]

One of the first things I did to my 240 was swap the stock alternator for a GM alternator. Mine was built for 160 amp output (left over from a never complete, long gone project), but a stock version at 105 amps would have suited fine.

 

I would suggest a higher output alternator, even if it just a later internally regulated version, like the ones found in the 280ZX. IIRC these were around 60A or so. Still less than I like to see, but a vast improvement over the 35A OEM alternator.

 

No car runs off the battery, with a "top up" from the alternator. If the car ran off the battery, then it would constantly drain, and the car would eventually shut off, relying on this mythical "top up". Before you get your panties in a knot, I've been working with automotive electrical and electronics for a couple decades now.

 

I would also suggest to not remove the battery from a running car, especially anything with sensitive electronics, such as ECMs, or radios. When a battery is disconnected from a running vehicle there are large voltage spikes that happen, on top of that the battery also serves to smooth out, to the point of removing the AC ripple that is produced by an alternator.

[Six_Shooter]

well this is how it was explained to me after a long drive,1000 miles, an over charged battery..... then repairs.

My alternators regulator was constantly charging my battery hence the over charged battery, a relay switch was fitted so when the battery needed a charge the relay would allow that.

So if the alternator runs the car, why would the battery need topping up on a 1000 mile drive?, in the day, no lights, no use of wipers , no heater fan......

The auto electrician  that found the problem explained like this, the battery runs the car and the alternator tops it up via the relay switch or the internal regulator of the alternator otherwise the alternator would be constantly on charge mode which would make the gas mileage bad, cook the battery......... maybe even over heat the engine .

 

If that really is what that guy said and worse believes, do me a favour and go give him a good smack, upside the head. That idea is so wrong.

 

An overcharged battery only comes from a failed regulator (internal or external, doesn't matter), that would allow the voltage to go beyond the 14.4 it should be charging at. To charge a battery the alternator must maintain a voltage of 13.6. This keeps the battery charged and has extra for the car to run on.

 

Even when you're not using lights, or heater fan, etc, the car still needs electricity for the ignition system, at the very least. The gauges all run off electricity, if there is EFI, the ECM needs electricity, so regardless of the accessories not being used, the car still needs power to run.

 

The battery should only need to be charged after start, and only for a short period.

 

The alternator runs the car, period, that is what powers the electricity in the car. The battery is only there for starting, well there is also that AC ripple filtering effect I mentioned earlier, but that's more of an added benefit than a design feature.

 

The alternator is supposed to be charging all the time the car is running. This will NOT damage the battery in a properly operating system. The only time anything gets damaged from the alternator is when a part fails, such as the regulator.

[d3c0y]

On a related note, what thermos are you going to fit?

 

I got two 12" thermos off bay 10 blade s-curve 1900ish cfm each 6.7amps each. I've got an old Davis Craig thermo stat lying around that I will use. Fans even came with a 3 year warranty and purchased from an Aussie store.

 

Looked at my alternator again and it's already converted to a ZX unit don't know how I missed that before.