"headlight harness" idea for heater fan....

[dogma420]

This would be directed at Z's on the brain, but also, just wondering if anybody else had any ideas; this might've been expressed already, and apologies if it has; I've been away for a while.

Before I get A/C installed in my 240, I want to ensure my fan, when put on high setting, has the same output at highway speeds as it does at idle.

I have a new honda fan, and the output at higher rpm's is incredible. This is extactly what I want from it all the time with A/C installed.

I would imagine that some sort of modification, similiar to the headlight harness / tail ligth harness if applied to the heater fan, where the current comes from the battery instead of the alternator, would make this possible....

Since I am electrically an idiot, anyone have any ideas?

My setup is just a stock alternator, and at this point I am not going to upgrade but probably will in the future, with probably using Arne's ideas on 280zx alternator...but that's not what I'm asking about here...

Thanks for reading,

Dog

[Zs-ondabrain]

Got ya! I'm looking into it and will post here at the first sign of success.

Dave

[hls30.com]

GR8!

Will

[Arne]

That'd be pretty simple, Dave. In the wiring behind the radio you'll find a blue wire with an inline fuse that connects to a red wire in the mini-harness from the fan switch to the fan. That's your hot power to the fan, and where the relay need to connect.

Relays have four terminals. One is a ground (often identified as '86'). Another is the hot lead, in this case from the battery ('30'). You'll want to use a good sized wire from the battery to the relay, and you'll want to put a 20 amp fuse or circuit breaker in it. I like to connect these things to the starter solenoid, not the battery terminal itself. (Just looks cleaner to me.)

The trigger wire ('85') is the blue lead with the old fuse. That fuse should probably be replaced with a much lower amperage, probably a 5 amp or so.

The new switched power lead from the relay ('87') goes to the red wire that was connected to the blue one.

This is less than ideal in a couple of ways, but about the only reasonable way to do it. One, the new relay will be triggered anytime the accessory position on the ignition is on, but to try to do it closer to the switch is problematic for this type of device with multiple speeds. Second, because we must do this upstream of the switch, there is still a fair amount of old wiring through which the current must pass. So the results may not be as dramatic as you might hope. But it might be worth a try...

[Zs-ondabrain]

That'd be pretty simple, Dave. In the wiring behind the radio you'll find a blue wire with an inline fuse that connects to a red wire in the mini-harness from the fan switch to the fan. That's your hot power to the fan, and where the relay need to connect.

Relays have four terminals. One is a ground (often identified as '86'). Another is the hot lead, in this case from the battery ('30'). You'll want to use a good sized wire from the battery to the relay, and you'll want to put a 20 amp fuse or circuit breaker in it. I like to connect these things to the starter solenoid, not the battery terminal itself. (Just looks cleaner to me.)

...

ARNE!!!! Did you seriously just advise ME on the workings on an automotive relay???????? :stupid: :stupid: :stupid:

Just kiddin. I haven't even had the time to look into it but I'm sure you hit it on the nose.

Dave.

[Arne]

ARNE!!!! Did you seriously just advise ME on the workings on an automotive relay???????? :stupid: :stupid: :stupid:

Just kiddin. I haven't even had the time to look into it but I'm sure you hit it on the nose.

Dave.

No. Dogma's real name is also Dave. I took so long to type my reply (stopped for lunch in the middle) that you got in before me.

Good to see you back, Dave (Zs-ondabrain).

[bjhines]

hmm.. linky... from a recent thread of mine...

http://www.classiczcars.com/forums/showthread.php?t=23409

There is one point to this that I have not tested... And I likely won't get to test for a long time...

Will the original heater resistors and wiring handle the higher current draw???...

If they will... what about the switch and the harness wires...???

The Fuse that powers the relay high current side is 20amps (that one inline behind the control panel... Oddly enough the circuit for the blower in the fuse panel had a 20amp fuse as well... though all it runs is the relay coil side(0.5amp)...

It would seem to me that I could leave the fuse panel wiring alone and only rewire the high current side of the relay (20amps currently)...

but that would still leave the original switch and resistors in the high current circuit..

I would need to source another set of resistors and another higher current switch in order to really improve the system wiring... That is a large task.. I think I will install this blower into one of my operational 240Zs to make sure it works without serious electrical modifications...

Another thought is that the original switch could be used if it were only operating a bank of relays that provided for 3 fan speeds... the only problem there is sheer complexity and added weight...

[bjhines]

and the conclusion on the motor draw.... at least static results... I have not tested dynamic impeadance...

OK... just got done testing resistance of the motors...

I used DC and turned the fan to dozens of positions and found this...

Original 240Z datsun fan::::::::::::::::::::::::::::::::

30% of the tries I got 0.7 OHMs

60% of the tries I got 0.6 OHMs

The Datsun motor showed variations(0.8, 0.9) at some points that would indicate wear and age... I tossed these out of the data...

Newer Honda 88-92 fan motor:::::::::::::::::::::::::::

90% of the tries I got 0.5 OHMs

5% of the tries I got 0.6 OHMs

5% of the tries I got 0.4 OHMs

... You might see a 25% increase in power usage... A 20 AMP fuse might not be enough when it ages and begins to stick... I think it will work fine though...

[bjhines]

I think the answer is much more complicated than just adding a relay... there is already a relay... the support wiring, switches, and resistors are not up to snuff either...

An additional relay will get you absolutely NOWHERE...

Trying to replace the original parts is not gonna happen with parts from your local radio shack... the fan is several hundred watts @ 12V... that is WAYYYYYYYYY over what anything in Radio Shack rack parts is rated for...

[dogma420]

you're the man Dave!

~dave

[hls30.com]

I think the answer is much more complicated than just adding a relay... there is already a relay... the support wiring, switches, and resistors are not up to snuff either...

An additional relay will get you absolutely NOWHERE...

Trying to replace the original parts is not gonna happen with parts from your local radio shack... the fan is several hundred watts @ 12V... that is WAYYYYYYYYY over what anything in Radio Shack rack parts is rated for...

Yes, that is sort of true-except, all of the needed parts are available in one stop shopping-the honda you pulled the motor out of... A few minutes of wire tracking and hacking, and all the necessary parts are collected. Any time I collect upgrade electrical parts, I alway pull the connectors-and usually the whole sub harness-that way I have the system as it was designed, and not stick a part in that happens to fit the space but not the system.

Will

[bjhines]

Well.. that is good if you have a pick and pull near you... I have to call in what I want and they pull it... it gets much more expensive if I have them remove every related part... many automobiles use multiple relays to control blower speed... the switches in those cars would be a step in the wrong direction... you could certainly make you own relay bank... but the Datsun resistors would still need to be reworked...

My measurements on the motor indicate it will draw only 25% more power anyway...

I think that the small wires used in the original harness are a major bottleneck... It would help to simply rewire the harness with 14 guage instead of the wimpy 16g and 18g the factory used...

The resistors are air cooled...

The switch can be cleaned and the contacts are pretty beefy...