Captain Obvious

And this talk about fans reminds me.... If you're looking for something under the dash instead of the engine compartment, there are two curious signals up above the fuseblock that show up on the upper middlish of the wiring diagram labeled as "To Cooling Fan Motor Sub-Harness". One of those wires is hot at all times and the other is hot in ON and START. You could use one or both of them to connect to your module, especially if you're locating it in the glove compartment. There was some discussion about these wires in the past in this thread: http://www.classiczcars.com/topic/46256-always-hot-connection-for-radio-install/

Gotcha. So you're looking for a low current source that goes hot when in ON. There's lots of ways to do that, but one of the simplest would be to tap into the white/black that goes to your ignition module and your ignition coil. That wire goes hot in ON and START

Bummer. If the Nikki pumps used balls pressed into counterbored holes on both sides, that's a tough one... Are the balls hardened? If not, one could drill (and maybe tap) them to extract them. I give it pretty good odds that they ARE hardened, but you never know. Some heat might also help with the removal as the aluminum case would expand more than the steel ball. Basically it's clear that they never intended those sealing balls to come out.

I'm not exactly sure what you would be using the 12V ignition signal for. Are you planning to use this connection as a high current source to actually power the fans? Because if so, then my answer is.. "There isn't one. Connect right to the battery and use a relay to switch the high current source." You would control the relay with a low current source that goes hot in ON and there are plenty of places to pick the up. On the other hand, if you're looking for that low current source that goes hot in ON to control a relay or a control module of some sort, there are several ways to do that. But I want to figure out if that's what you're looking for first.

Steve, Wow. You really went for a prepackaged fancy "module". I was picturing one of these more generic versions. Something that doesn't even have a case to facilitate ummm... curiosity http://www.amazon.com/gp/product/B00XE965RG?gwSec=1&redirect=true&ref_=s9_simh_gw_p60_d0_i3 So I guess if your module doesn't work out, you're out a whole two dollars and seventy cents. On edit - I like the uber generic description of that module I linked to! Do you think they could have gotten any more buzzwords in there?? DC Motor Speed Control Driver Board 3V-35V 5A PWM Controller Stepless DC 3V 6V 12V 24V 35V Variable Voltage Regulator Dimmer Governor Switching Build with LED Indicator and Switch Function"

Hahaha!!! Nice Janglish! I'd not noticed that before. Thanks for pointing that out. Reminds me of something I often see at my local Asian supermarket... They sell "Beef For Stir Fly". I've been tempted to bring it to their attention, but don't want to accidently risk an incident. Yeah, unless that four wire PWM does just tie the two positives together for ease of wiring, grafting that thing into the Z wiring would be a pain. You still need the green/white to go to the parking lights, but want to separate it from just the dimmed lights while leaving the un-dimmed ones alone. Let's hope it's just a tie point for ease of wiring.

One other thought... Maybe they're simply tying the positive out right to the positive in on the PCB... It might be a simple PWM to ground through a transistor and the only reason they included a separate terminal for positive out was to simplify the wiring for people who didn't want to put two wires under the same terminal screw? Without having one in hand to do a little reverse engineering I can't tell.

Hmmm... On those pre-canned four wire dimmers, it looks like they're actually DRIVING the output terminals instead of just pulling one of them to ground through a transistor. Two of the connections are easy: Negative in would connect to ground. Easiest place to pick this up would be the black wire at the dimmer connector. Negative out would connect to the low side of all the bulbs. Easiest place to pick this up would be the red/blue wire at the dimmer connector. But the other two connections are a little problematic... You would have to break the original connection between the combo switch and all the dimmable bulbs to insert the module between the two. Hate to suggest that you spend more $$ if you're already in the doghouse, but can't you just pick up a low side switching PWM controller like I used? Something that shares the same low side and just drags the bulbs to ground through a transistor? Would certainly be easier wiring! You'd make up the cost in time spent with your head underneath the dash! You want me to pick one up at the yard and send it to ya? My treat!

Steve, Haha!! Yes, I'll take the blame. I'm glad to shunt the heat since it's harder to feel the impact when I'm so far away. You're one of the people who are partially to blame for this anyway. Showing off your LEDs in Memphis and all. So, about the electronics... The PWM controller is typically a three wire device: First connection gets connected to a source that goes hot when the bulbs are on. Second connection is the interrupted PWM output which gets connected to the low side of all the bulbs you want to light. Third connection gets connected to ground. Problem is that the original pot is a two wire device, so you need to run a new third wire to the PWM controller. Or.... Through a little electronic Tomfoolery I modified the PWM controller circuit inside the box to make it a two wire device instead of a three wire device. I'll get into the details if anyone wants, but I basically traded a small bit of PWM adjustment at the upper end for the ability to eliminate the third rail. So instead of operating from (0% to 100%) mine now operates from (0% to ~98%). I don't miss that upper 2% of "full brightness" duty cycle. And in the unlikely event that you DO miss that upper 2% of brightness, you can switch to brighter bulbs or something. Only other trade off is that I'll need to keep one incandescent bulb somewhere in the system or bury a lowish value resistor in place of a bulb somewhere in the system. So you either need to add the third wire (which is also easy) or you can modify the controller to use two wires instead of three. I decided to modify the controller but either way would work.

SteveJ nailed the "why".... I'm messing around with LED lighting for the dash and the original resistance based pot style dimmer doesn't work properly. The original dimmer pot is 10 Ohms and has to be somewhat "matched" to the impedance of the original incandescent bulbs in order for it to work properly. When you go to LED's, the impedance is so radically different that the dimmer function doesn't work effectively anymore. Besides... It's cool? The PWM controller does contain electronics, but I doubt there's anything programmable in there. It's just a fixed frequency oscillator that they use to drive a variable pulse width output to a power transistor. You turn the knob and it varies the pulse width from 0% ON up to 100% ON. "You seem to be making a lot of brass extendo devices..." Haha! Because I can.

Most vehicles have long since changed away from a potentiometer based instrument dimmer to a Pulse Width Modulated (PWM) based electronic dimmer controller and I've been working on retrofitting one of these newer style electronic dimmer controllers into my 280Z. I poked around the junkyard looking for one that would mechanically fit in the original potentiometer location and settled on one from a late eighties to early nineties Toyota Camry. The main criteria needed are short stubby mounting depth and rotate control instead of a thumbwheel so I could mount it in the original dimmer pot location. This is the dimmer out of a 91 Toyota Camry: The biggest hurdle with this retrofit is that the shaft is too short, and because of that, this became mostly a mechanical project instead of an electrical one. I took the dimmer module apart and took the control potentiometer out: Mounted the pot in a "specially designed fixture" to be able to modify the shaft. I wanted to turn it down a little to fit inside an extendo-shaft. Here's the pot mounted in the fixture and the rough cut brass extendo-shaft at the bottom: I turned the pot nub down a little and bored the end of the extendo to fit onto the pot nub. After the rest of the machining is done I'll epoxy the extendo to the original pot nub: : Then for the other end of the extendo, I machined some splines to fit the original dimmer knob: Here's the completed dimmer next to the original dimmer pot. I glued the shaft together and everything looks great. I didn't mount it in the dash yet, but I did connect it up and it works great. I probably won't mount it in the dash until the off season. I'm going to pull my dash out for some HVAC work and it'll be a lot easier to swap the original pot out with the dash out of the car. Here's the completed dimmer:

I made the extendo contact. It's just a little piece of brass stock that I drilled and tapped for a small screw. Don't remember the size though. About the only dimension that matters is that its not so big that it hits other places you don't want it to hit. Not sure when I'll be in there again, but I'll measure it for you next time if you want. I think I'll have my dash out again this coming off season for some changes and if you haven't fixed yours by then, I'll have my wheel off then and can refresh my memory.

So after I did my steering wheel upgrade, I made sure my horn was working and it worked great. Then one day, I'm out driving around and making a turn and some guy pulls out in front of me. I hit my horn button and nothing. Doesn't work. Get home and test the horn again. Works fine sitting in my driveway... Turns out that my horn worked great AS LONG AS THE STEERING WHEEL WAS POINTED STRAIGHT AHEAD. But if the wheel was turned to one side or another, the slip ring contact lost contact and my horn didn't work. That took me a couple weeks and two near misses on the road to figure out. In the end, I made a little extendo contact and screwed it into place. Works great. Here's my original worn one and my replacement. The new one should last longer than I do.

If you're looking to get rid of the redundancy, you could get the upper warning lamps from a 75. Left side says "CATALYST" and right side says "FLOOR TEMP". That way you could fill all the available locations with unique indicators. I'm an idea guy. Never said they were good ideas though...

That makes sense. The other pics of the car look clean. I was surprised the heater box was that dusty. Good luck with the re-sealing. Hope your toes are toasty and your windshield clear.

Haha! Well as I said. More power to ya! I'm just glad there was a spot for my PO to put my antenna toggle without having to really kludge something together. If it weren't for that unused plate, I'm not sure what he would have done. So you're still running the original radio with the switch in the faceplate?

Glad to help. As dirty as your heater box was though, I can certainly understand why you were thinking a filter was necessary. That thing was a dirty dusty mess! Was the entire car like that when you started?

Agreed!!!

Sounds like a plan. I think there are a couple other threads already about people who have "re-foamed" their heater boxes. Search around a little and I bet you can turn up some ideas.

I assume it was provided in all 75 cars regardless of the destination. OK, so we got the "What" detailed out... Now how about the "Why?" Out of curiosity, why is it you're doing this? I mean, it's obviously a "style" choice kind of change, but it just seems funny to me to replace a perfectly good blank block off plate with a non-working redundant indicator lamp. More power to ya. but just wondering...

Haha! Floppy dirty pieces of foam and vinyl! One of the Z specific stores might sell pre-cut replacements, but I haven't looked. I think most people just use regular hardware store foam and fabricate their own. As for if it's really necessary or not... It's nice for the doors to seal well when you have them in the desired positions., but not a deal breaker if you get a little leakage past them. If you're in that deep, I'd put something in there, but it doesn't have to be perfect?

I think I figured it out... 74 had no fuel warning lamp. 75 had the lamp between the defroster and fasten seat belt lamps. 76 moved the fuel warning lamp up to new position to the right of the map light. So my belief is what you have there is a 1975 fuel warning lamp. In 75 they used both lamps up by the map light for the catalytic convertor warnings Take a look at pages BE-42 and BE-96 of the 75 FSM. Also take a look page 29 of the service bulletin the described the differences between 76 and 75.

And here's a shot of the interior of my old 260. It doesn't have that hole at all. And prior to the 260, the whole dash and console area was completely different. Here's the 260: :

This is from page 16 of the 1977 Owner's Manual. I assume 78 is the same:

George, I don't think there ever were any filters in the heater system, so I'm confused... If you're thinking those floppy dirty pieces of foam and vinyl were filters, then you're incorrect. I think those are just for internal sealing of the duct doors and insulation, not filtering. Is that what you're talking about?