here hoping satch or someone with asuch knowledge will have some insight and guidance for my ability or lack of to diagnose electrical. ive done a couple hours searching and all come up with light switch or harnesss which ive ruled out.

the vehicle is an 89 FC. earlier this morning drive my brother to school and went home. an hour later I went to start the car and notice the radio wasnt working. ignored it then pulled out and turned left and noticed my blinkers werent working. the relay was clicking but no indicators on the dash.

sure enough i check everything and the list is,
brake lights
parking lights
interior lights
seatbelt retractors dont retract to doors open or closing
and radio.

headlights work though.
ive verified that its not the headlight switch or wiring. swapped with known good units. i then checked all fuses and all are fine. i then took the multimeter and probed all fuses and found none are reciving 12v at all regardless of ignition position...this is where i am at currently.

ive never tinkered past the fuse box before so im in uncharted territory as well as it being s5..

any ideas guys??? help a brotha out.

 

You pulled the fuses out and checked them visually? Anyways, shouldn't be a fuse since the problem is on all kinds of different systems. But did you check the ones under the hood anyway, just to rule them out too?

Yes, wouldn't be headlight switch (since your brake lights don't work). Just gotta find the common denominator to all those systems not working. Easier said than done.

 

yea lol. i visualy inspected all fuses in an out the car. is there a way to trace where the fuse box gets its power?

 

it seems more like my body harness has lost power in general. the cigg lighter doesnt work now, nor does the factory alarm light and beep when i lock the doors aswell as the glovebox light when turning the switch on.

how can i trace power to the fuse block? car starts and runs fine. the dash dials even work aswell as the logicon. byt no lighting.

 

If you are finding fuses which are not being fed power regardless of key position then you need to focus on the ignition switch and its connection to the Front harness. Under the dash along the steering column you will find the plugs which connect to the Ignition Switch (should four in all). One of the plugs has two wires and has a Blue wire and a Black/Red wire. The Blue wire receives power w/key to ACC and this wire runs to the fuse box to power the items in the ACC circuit. The Black/red wire powers the IG2 fuses when the key is set to on. So you need to check both of these wires for voltage. Blue wire w/key to ACC has power and Black/Red has power w/key to on. If they both have voltage as stated then the problem is more likely related to the connection on the back of the interior fusebox.

 

will do. ill keep you guys posted.

 

get the alt tested just incase I had a similar prob like that last year and my alt was way bad lol

 

check the underhood btn fuse

 

Has the dash ever been removed?

 

edit: I'm checking the wiring diagram to see if we can figure this out...

Does your horn work?
Clock in the idiot light cluster?

Unplug headlight switch. I know you said "ive verified that its not the headlight switch or wiring. swapped with known good units", but how did you check the wiring? Visually? On the harness side, light switch plug, check if you have battery voltage at the following wires (ground the negative lead of the test light or multimeter): R, R/W, W/G

Not sure what your experience is with wiring and electrical testing. Let me know if I'm going too slow or fast.

edit: link to FSM, wiring diagram near bottom http://mazdarx7.iougs.com/fsm.shtml

 

This is an important thing to do. If the fuse is good make sure the White/Red wire coming from it is has constant voltage to it (no key necessary).

 

^ Related question...anyone know what BTN stands for? Always wondered.

K, back on topic

 

Not sure, but I thought the B stood for battery, but who knows. This always baffled HAILERS.

 

no idea but if it blow you loose most interior functions excepting headlights. I know it feeds most connections in the interior box.

 

"back to normal"

 

Holy Replies Batman. lol My cousin is on his way over with the car so i will have some info up in the next hour.

On a side note.. I received my new oil cooler lines for my s4 tii. and now i can go brap away once again!!

 

::UPDATE::
Alright so I tested the Blue and Black wires from the ignition switch plug and both are getting voltage in their positions. I also checked the BTN fuse aswell and its fine.

HOWEVER. Checking the White/Red under it with one lead on it and the other on the negative terminal Im not getting any power at all.
As for the Light switch and harness i did a continuity test with all the pins and they all checked fine.

So. Does this mean the fuse box isnt getting power because of the BTN not getting power? or does it not work that way?

 

The fuses in the interior fusebox powered by the BTN fuse would not be receiving voltage. Apparently the White/Red wire is loose from the BTN fuse.

 

Yea thats what im learning right now with the FSM.
What do you mean loose? As in its loose going to the interior fuse block?


Just to clarify this is what i did.

I unbolted the engine bay fuse block and unplugged the connector to the BTN fuse and probed the WHITE/RED wire and the negative terminal on the battery. My Multimeter read 0.00v.

How exactly does the WHITE/RED get power? straight from the battery?

 

The battery powers all of the fuses in the engine fusebox. The W/R wire receives power from the BTN fuse thus the wire has to be connected in some form or fashion to this fuse. If you disconnect the W/R wire then you are shutting it off from voltage so of course it won't have any voltage. Both sides of the BTN fuse should have power. If it does not then use the continuity function of the multimeter to check this fuse.

 

I did it again your way and sure enough ive got 12v to the BTN. The Fuse has Continuity too

 

So, you have power to the fuse and the fuse checks out okay, but you still don't have voltage on the W/R wire?

 

double checking..

 

OK. Probing the WHITE/RED and the Neg terminal I get no voltage. If i move the lead to the positive term. i get -12v.

with it plugged in like you said.

 

hmm. If it only reads if i put the other lead on the positive terminal does that mean its grounding out somewhere? or is that not important at all?