wingnutooa Posted February 10, 2009 Share Posted February 10, 2009 Okay...77 280Z just got done putting the dash back in. i recently had everything pulled out to solder some wires that had been chewed by a mouse. i new it needed done but decided to dig in when the heater started blowing fuses and then the entire car died. so i fix everything i can find. in my quest to put the battery back under the hood where it belongs and get the ginormous cable out of the cabin area, i found the "crimp" job on the positive cable, guilty of killing all of my electronics. so i fixed that. and decided to fix the negative while i was at it. got everything put back in and put back together with the exception of the A/C box because i dont need it. and i dont have the glovebox or center instrument panel/trim piece in yet. (easier access through those holes. the car starts and runs. everything works fine, i even fixed the horn button. so i try the heater. and it blew the fuse. i'm not really understanding this because i hooked some jumper wires to it while it was out of the car and it almost took off in flight. is it possible that its got too much drag for the 20A fuse? thats a pretty big fuse.... any ideas? i'm going to try a couple other things today... i'm going to unplug it and turn the switch on, if it blows a fuse then its not the motor. then i'm going to jumper the motor again via the fuse panel and see if it blows a fuse. any thoughts on where else to look? Quote Link to comment Share on other sites More sharing options...
dan5138 Posted February 10, 2009 Share Posted February 10, 2009 When you 'turn the heater on' are you referring to the blower moter, or the rear defrost? To the best of my knowledge, all the doors and heater controll valve are vacuum controlled in the 76+ Z's. If it is your blower motor blowing a fuse, pull the motor out make sure it spins freely. if you can check the brushes, do that too. The blower motor in these *should* draw less than 20 amps. Hope this helps some! Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 10, 2009 Author Share Posted February 10, 2009 yes i'm referring to the motor itself. the rear defogg is on a seperate circuit, although it also is a 20A. the motor spins freely and when i hook it up to 12 volts it goes without problems. going to try and test how many amps it draws while running. Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 10, 2009 Author Share Posted February 10, 2009 OKA...okay so its not the motor. i unplugged it and it still blows fuses. i unplugged the resistor and it does NOT blow fuses. so i pulled the resistor out of the blower motor housing. the smallest coil had some rusty gunk connecting the coils so i cleaned it up... to no avail. next i started checking for power. okay so both of the wires that plug into the fan have 12V to them. after i ran out of options checking for power and cussing my wiring schematic because its not 100% right, i started looking for ground there's a big black wire going to the back of the switch. i'm assuming ground. its got continuity atleast. when i switch the fan switch the continuity from the black wire moves from lead to lead on the back of the switch. so here's my assumption the fan has 12V going to it through both wires. when you turn the fan on, it lessens voltage to one of the wires creating an imbalance and a current. the greater the imbalance the higher the current and the faster the fan goes. and this still does not solve my problem. when i unplug the resistor it does not blow fuses i'm assuming because the circuit is open. when i plug it in it closes the circuit and alows power to flow to the "short" how can i find this short. has anyone ever worked on the heater or switch and where am i supposed to have power and where am i supposed to have ground. Quote Link to comment Share on other sites More sharing options...
dan5138 Posted February 11, 2009 Share Posted February 11, 2009 Don't quote me on this... But you should have one power wire (+) going in to the switch, and possibly one other wire for the A/C compressor. The compressor clutch and blower motor *might* share a fuse. From the switch you should have 3+ wires that go to the resistor. From the resistor you should have 1 wire going to the motor to power it up. The 2nd wire on the motor should go directly to ground. Could try puting a 30 amp fuse in and seeing what happens. I would try replacing the resistor. Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 11, 2009 Author Share Posted February 11, 2009 okay so last night i found the problem the little plastic plug on the harness side of the fan connector has two spades. like this [|-] the sideways one must have gotten warm enough to melt the plastic a little and it slid over into the other one. i noticed after i started examining the harness better and the one i was getting 12 volts from that is supposed to be ground, doesnt go anywhere. like power from a mystical battery. so then i started looking at the plug more and noticed they were touching. i think it just shorted again this morning though because my girly just called and said the heat quit again. i'm just going to take that plastic plug out of the loop. Quote Link to comment Share on other sites More sharing options...
woldson Posted February 12, 2009 Share Posted February 12, 2009 i think it just shorted again this morning though because my girly just called and said the heat quit again. Heehee, she you test "monkey" Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 12, 2009 Author Share Posted February 12, 2009 yeah she's been hoofin' it for over a month waiting for me to get the car back on the road. GOOD NEWS! not only did the heat quit but the car still intermittently dies randomly... so its like i never took the car apart. its parked at the 76 station where i had to leave it last night being night time though it gave me some insight on where to look. before i thought ALL electronics were cutting out. well the hazards still worked and the park/ headlights still worked. that means the power thats being cut is my switched power i'm going to start at the back of the ignition switch. Quote Link to comment Share on other sites More sharing options...
woldson Posted February 13, 2009 Share Posted February 13, 2009 Good luck! Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 13, 2009 Author Share Posted February 13, 2009 It WAS the ignition switch. so i got lucky there. i'm not really sure why the heater fan blew another fuse, I checked the wires, put a new fuse in, and its been doing fine since. Maybe I just had a bad fuse. Quote Link to comment Share on other sites More sharing options...
islanddozer Posted February 14, 2009 Share Posted February 14, 2009 These fans are notorious for bad grounds. Check the ground from the motor. I have bypassed the ground many times for these heaters. Just run a new ground to replace the original. Quote Link to comment Share on other sites More sharing options...
RigilKent Posted February 14, 2009 Share Posted February 14, 2009 yep i agree its a ground i have had a few problems similar in my 81. threw an extra ground on there and it seams to be fine Quote Link to comment Share on other sites More sharing options...
wingnutooa Posted February 17, 2009 Author Share Posted February 17, 2009 well it wasnt the ignition switch. it decided to fool me and run for a couple days before doing the exact same thing. this time i was almost an hour from home. i'm done messing around with it. i'm gutting the entire interior and buying a new wiring harness and possibly a new computer or ECM or ECU or whatever they're called. i'll just do carpet and new doorpanels/seat covers at the same time. then all i'll need is paint. sweetness.... but right now i've got to fix a truck i just bought... 95 6.2 diesel. runs like a champ but supposedly has a blown head gasket. 3/4 ton 4x4. 1,100 bucks WHOOO. so the datsun is after that. Quote Link to comment Share on other sites More sharing options...
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