72 240 heater fan (honda mod) stopped running today...

[dogma420]

Hey DAve,

I am not going to argue or anything like that, I just wanted to point out my point of view--

There is one point of my Z that I've always been proud of, the electrical system has always been perfect, as close to original and the kind of condition that a restorer of a 72 concours would have in their system, the fuse box looks perfect,etc....(not saying that I haven't missed something and it'll blow up tomorrow, but imo), and whenever I've had the chance, Ie. I've had the dash out, etc....I've always throroughly checked all the wires and all the wires that were possible to electrical double 'double-time' under the dash I did do this to.

My issue with the plastic fuse holder on the heater melting was actually quite minor....I guess my description did not do justice....the melting is that it looked brand new from the outside (the original) but the edges were essentially glued together, so no matter what I did to twist I couldn't get it off. So I applied probably unnecessary force so I cracked it when I removed it.

I run it on full blast almost exclusively during the Winter, so that's why I bumped to 25 amp....I don't feel that's an issue, simply because I sometimes feel that certain circuits have smaller amp fuses based on the part, and not the wires. Would I be wrong on that? To me personally, I don't have the specs, but I would say the power output in Amps is at least worth a 5 amp increase in the fuse, and that the wires are only rated at 20 amp before they would fail.

Am I wrong?

CC'd to your new thread as well.

By the way, Congrats to Enrique for getting his letter printed in Winter 2007 Nissan Sport Mag--probably our best tech writer/answer on our forum representing us very well!!!!

PS. Dave, I've taken apart my combo switch carefully, cleaned it all up, sprayed / clean liberal tuner spray and made it as good as possible imo without replacing the metal pieces that are rubbed on.

It works great other than that. Did you by chance get a hold of new contact pieces for the light/wiper contacts? Just curious. Mine are horrible, just normal wear over 30+ years.

[bears240]

just reading you post and decided to look at the wiring diagram in the haynes guide and it shows a 30 amp fuse for the blower motor(seperate inline fuse) for both the "240z basic model s30 series usa" and the "240z late model s30 series usa.- manual and automatic transmission. pages 168, and 169 haynes manual.

[a7dz]

I run it on full blast almost exclusively during the Winter, so that's why I bumped to 25 amp....I don't feel that's an issue, simply because I sometimes feel that certain circuits have smaller amp fuses based on the part, and not the wires. Would I be wrong on that? To me personally, I don't have the specs, but I would say the power output in Amps is at least worth a 5 amp increase in the fuse, and that the wires are only rated at 20 amp before they would fail.

Am I wrong?

YES

You design a circuit to its current draw then size the wires and fuses to meet those requirements. The fuse is to protect the complete circuit.

Being a professional in this field over thirty years I still stand with my post above do not over fuse these circuits!!! I believe the whole purpose of the upgrade harnesses that Dave builds is to decrease the current load on this antique wiring. Why would you willing increase It???? Then go on to say that you run the motor and its max current draw at the same time!!!

SNIP... Did you by chance get a hold of new contact pieces for the light/wiper contacts? Just curious. Mine are horrible, just normal wear over 30+ years.

Then put this statement after words saying you know your electrical systems are wearing out?? Its like saying Doc I know I have cancer in my throat and lungs. Please remove the cancer in my lungs but don’t worry about my throat because I like to Cough.

[a7dz]

just reading you post and decided to look at the wiring diagram in the haynes guide and it shows a 30 amp fuse for the blower motor(seperate inline fuse) for both the "240z basic model s30 series usa" and the "240z late model s30 series usa.- manual and automatic transmission. pages 168, and 169 haynes manual.

That is one of the errors we have discovered over the years. I have never found a car wired that way. The only way I have seen them wired when there is a accessory relay is with two 20 amp fuses one goes to the rear window defogger switch the other the fan motor for the heater.

I posted a thread here a while back asking members to remove their accessory relays and then turn on the heater motor. With the accessory relay removed not one of the heater motors ran.

I beleive that blower shown on the inline 30 amp fuse by itself is a electric cooling fan for the radiator. I have never seen on installed. Nor have I found a wire harness built that way.

[Zs-ondabrain]

So roughly, It's only a matter of time before the circuit fails, whether that be a fuse blowing, a metel switch contact no longer working or the worse scenario, something melts and or catches on fire.

Don't get me wrong, it may NEVER have a problem. Weird things like that happen all the time. Hell, I drove home in my 510 with a hole in the block once without failure, but had I drivin one more mile, It most likely would'nt have made it. But I'll never know.

So what me and Jim are saying is, Don't push your luck, especially with a 33+ year old system. It only takes that 1 extra mile.

1) Make the switch like new via a rebuild or new switch

2) Rewire the circuit in question with new wires

3) Clean every contact in the circuit, connectors, fuse clips, everything.

4) maybe even go as far as pulling the fan motor apart and cleaning the hell out of it.

If my situation were the same, I would'nt increase the fuse size till I reinforced the rest of the system. But that's just me.

Dave, (Dogma420) I was never under the impression that you were starting an argument, and I always listen to some ones point of view. Don't sweat it.

Dave

AKA DatsunDave (OLD nickname, rarely used till recently)