1973 240z Custom Wiring From Scratch

[Matthew Abate]

Looks like the electric fans MSA and Z Car Depot are selling are pulling between 10 and 25 amps. I’m going to look further but I’m speculating that 12 AWG would be sufficient if those numbers are accurate.

However, if I need to go above 30 amps, the tech rep at Eaton recommended this stand alone relay/fuse power relay module they make.

https://www.eaton.com/us/en-us/catalog/emobility/series-37700-pfm-prm.html

[Matthew Abate]

Update:

I made a major decision to scrap the electric fans. After much digging around I had three major issues that were not insurmountable but we’re hanging me up and not really worth the effort.

1. I could not find a relay module that could handle 40 amps and had a provision for 6 relays (headlights, parking lights, and fans). I found some from MSD that can hold 1, 2, or 4, and I could gang them up, but it was getting sloppy. On top of that the extra wiring was not appealing.

2. Making sure that I was pulling at least as much air as the mechanical fan was also starting to become a mess of options and getting a fan shroud that works with the various radiators I am considering, fits fans that pull enough air (>2,800 CFM total) was not impossible but was giving me a headache.

3. Buying everything necessary to do an electric fan setup is more expensive that replacing my mechanical fan (or refurbishing my old one) and having been out of work for seven months now, I can justify that.

So, I am probably going to get a new fan and clutch, buy a fiberglass fan shroud from MSA, and call it a day.

Now back to our regularly scheduled programming.

Edited July 18, 2023 by Matthew Abate

[dutchzcarguy]

On 7/17/2023 at 4:16 PM, Matthew Abate said:

Looks like the electric fans MSA and Z Car Depot are selling are pulling between 10 and 25 amps

Just my opinion.. but i don't get it when people go for a electric fan to cool.. they use a lot of energy.. that's why there is a big mechanical fan on a engine.. no they say i first go make a lot of electric energy (Big generator/alternator and even fatter cables) with my mechanical engine, then i make with a big electric motor a lot of mechanical energy to cool.. that's energy lost twice!!!!!  🙈

The only time a electric fan is useful when the mechanical one can't keep up!!  This was done in a 300zx twin turbo.. they have both "sorts" of fans.. then it makes sence..

As i said just my opinion! 😉 

Edited July 19, 2023 by dutchzcarguy

[grannyknot]

2 hours ago, dutchzcarguy said:

Just my opinion.. but i don't get it when people go for a electric fan to cool.. they use a lot of energy.. that's why there is a big mechanical fan on a engine.. no they say i first go make a lot of electric energy (Big generator/alternator and even fatter cables) with my mechanical engine, then i make with a big electric motor a lot of mechanical energy to cool.. that's energy lost twice!!!!!  🙈

The only time a electric fan is useful when the mechanical one can't keep up!!  This was done in a 300zx twin turbo.. they have both "sorts" of fans.. then it makes sence..

As i said just my opinion! 😉 

An electric fan comes on only when needed, mechanical fan is robbing power from the engine all the time regardless of whether it's needed.

With the E fan off, as in hwy driving and the M fan has been removed, there is more power available to the rear wheels, not much more but some.

[Patcon]

Electric fans can also be setup to come on with the AC or speed up when the AC is used.  Another anecdote, if mechanical fans are superior why are they pretty much no longer used on new vehicles?

[Mark Maras]

2 hours ago, Patcon said:

Electric fans can also be setup to come on with the AC or speed up when the AC is used.  Another anecdote, if mechanical fans are superior why are they pretty much no longer used on new vehicles?

I think they stopped using them because they rob horsepower anytime the engine is running. Although they seem to be unpopular on this site, I ran a flex fan on my 240 for many years after the fan clutch locked up. I did notice the slight gain in horsepower (butt dyno) and it cooled just fine.

[Patcon]

I suspect a number of reasons:

With fuel injection you get really precise temperature control for emissions purposes but only when you need it

Faster warm up to reduce emissions

More horsepower

The ability to strip heat away faster when the AC is running

No big mass on the front of the engine spinning around that can potentially disintegrate

That's all I can think about off the top of my headache 😞

[SteveJ]

4 minutes ago, Patcon said:

I suspect a number of reasons:

With fuel injection you get really precise temperature control for emissions purposes but only when you need it

Faster warm up to reduce emissions

More horsepower

The ability to strip heat away faster when the AC is running

No big mass on the front of the engine spinning around that can potentially disintegrate

That's all I can think about off the top of my headache 😞

Well, most non-trucks have transverse mounted engines, so they aren't positioned for an engine mounted fan to draw air through a radiator.

[Patcon]

That too.

Although all my BMW's are 😉

[billgtp]

Won"t get into the pros and cons with electric fans. But for me its the only why to go. Did it on my 32 ford that I built. 

Matt on your relays I went though the same problem  Spend all kinds of time at junk yards on the net looking for a relay box. Ended up having one made for me. You can go to any Hot Rod or custom car shop that does real fabrication work and they will build a box for you. Mine cost me $50 plus materials. I mounted it in front of the battery mount. Now my car had been hacked by POS where I even had to replace the right side if the firewall. First pic is relay box the lid has rubber seals on it to keep moisture out. It has a power relay to supply the relays above it. A ford enertia switch controls ground to fuel pump relay

[Matthew Abate]

Very cool!

Where I’ve netted out on this is as follows: I am going to punt on the decision to go electric or not until I am closer to starting the car. In the mean time I will build the provisions for an electric fan into my engine harness and if I don’t use it I’ll tuck it away.

Edited July 20, 2023 by Matthew Abate

[Matthew Abate]

I have been struggling to design a relay box that could fit where I want it to go and contain everything I want in it, but this morning I had an epiphany. If I can get the relays I am adding for the lights under the dashboard I don’t have to worry about it. So here’s my question:

Has anyone figured out how to squeeze four more relays under the dash without them being seen? Keep in mind I have an air conditioning evaporator under there already so I think most of the space that would be there normally is already gone.

I’m wondering if it’s possible to rebuild the relay board on a sheet of ABS to fit in the original location but fit 4 more relays. I’m going to look into that.

If that’s not going to work I need to find a new spot in the engine bay which I don’t like.

Edited July 25, 2023 by Matthew Abate