Secondary Fuse Box/ Voltage Questions

Post by **subzerocarfanatic** » 06 Dec 2019, 20:33

This question goes along with my last long one about the wiring and voltage. My question is, where does the power going to the fuses in the big secondary fuse box .
(the one by windshield engine bay) get all of it's power from? Does the power come from battery B+ Cable to the Relay/Main Fuse Box then get routed through the 50 and 60 AMP Fuses to the other 15 Amp fuses in the main relay/fuse box and from there into the secondary fuse box by windshield then get fed to the ECU or ECM Whatever it's called? I need to know how the power is filtered in what order so that maybe it will help me figure out if and why I have less than battery voltage at fuses 1-4 and 19-21 in the secondary fuse box. Do the headlights need to be on in order for the fuse related to headlights to show 12 volts or should all fuses in the secondary box always have 12 volts when key is on? One last question to this topic, before i turn the ignition key on it showed 12.15 Volts at the battery with my meter, after key was in on position (position II) the battery showed 11.83 volts, is it normal to drop that much from just turning key on?

Post by **abscate** » 06 Dec 2019, 20:35

One last question to this topic, before i turn the ignition key on it showed 12.15 Volts at the battery with my meter, after key was in on position (position II) the battery showed 11.83 volts, is it normal to drop that much from just turning key on?

It indicates the battery isn’t holding charge, it’s dead.

This might explain why you see such varying voltages. Anything with a load on it will drop the voltage on that circuit. Something as small as a glovebox light will do this.

Post by **wizechatmgr** » 06 Dec 2019, 20:36

Try checking for voltage drop between battery + and the B+ lug on the aux fuse box before you spend any more time.

The voltage drop you are getting provided the lights aren't on appears to be excessive.

Post by **subzerocarfanatic** » 06 Dec 2019, 20:37

I checked it when the car was running and it always shows well over 13 volts, what gives my friend!

Post by **abscate** » 06 Dec 2019, 20:39

That’s reading the alternator output , not the battery. It actually should be closer to 14 V with the car running.

Post by **subzerocarfanatic** » 06 Dec 2019, 20:41

it was 13.89 i believe, i will go check real quick. BRB

Post by **subzerocarfanatic** » 06 Dec 2019, 20:58

writing down my findings.....

Post by **subzerocarfanatic** » 06 Dec 2019, 21:44

OK... here we go! With key on battery voltage on the battery itself drops as i mentioned prior, and the longer my key is on the lower the voltage gets so keep that in mind. Fuses 1 - 5 in relay/ fuse box all have battery voltage with key on. Fuses in secondary fuse box are as follows, fuse 1 = 3.4 Mv, fuse 2= 48.3 Mv, fuses 3&4 = 11.61 Volts. fuses 5 - 17 have battery voltage, fuse 18 = 11.66,
2nd row of fuses in secondary fuse box, fuse# 19 & 20 = 9.8 Mv, fuses # 21 & 22 =8.9 Mv, fuses # 23 & 24 = 4.6 Mv, Fuses 25 - 36 all have battery voltage. Key off battery voltage on battery itself = 12.09, key on = 11.80, B+ LUG with key on 11.80, key off = 12.09. I do have driver side headlamp unplugged from the car. think i need to charge battery again. Any ideas guys??

Post by **wizechatmgr** » 07 Dec 2019, 03:56

Charge it, it is low. Could be a battery on the fritz...

Post by **kranz** » 07 Dec 2019, 05:32

How old is your battery?