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Discussion Starter · #1 ·
With the ignition off I have 0.66 volts at the radio (red wire) and cigarette lighter, engine off. Engine on is 0.88 volts. The 7.5 amp accessory fuse, 10 amp mirror fuse and 15 amp audio fuse under the hood are all good. The yellow “keep alive” wire to the radio is dead. Battery shows 11.88 volts off, 13.50 volts running.

This whole mess started when I found the radio on (aftermarket radio) as I was walking by the truck. Several times the battery was dead after we suspected the radio somehow turned on after shutdown. The radio is supposed to turn on when the engine is started and turn off at shutdown. I had 12 vdc at both the red power wire and yellow keep alive wire earlier this am.

2003 Nissan crew cab with power door locks

thanks,

len
 

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Sounds like you might have a problem with the Accessory Relay. The lighter socket and power socket actually have separate fuses, the power socket is direct but the lighter goes through the Acc Relay. If the relay contacts are stuck in half-a$$ conductance, the half-a-volt you're seeing on the circuit may be enough to keep the Acc signal gate in the radio turned on. The relay is here on the back of the cabin fuseblock:
Circuit component Font Rectangle Parallel Auto part
 

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Discussion Starter · #3 · (Edited)
Thanks for the info. All fuses every where check fine. I can feel and hear the relays click however I'm going to pull the relays this afternoon. The truck only has 120K on it and I'm the second owner.

Thanks again

Len
 

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Discussion Starter · #4 · (Edited)
Pulled all the relays, part number 252309B900. They are all the same. Swapped them around with no real change. Engine off voltage is 1.88 vdc, running 2.01 vdc. Better but still no voltage at the radio connector and the voltages poster here at the yellow keep alive circuit.

I traced the radio power wire back to the connector at the fuse box. Green wire with a red trace. It reads 1.88 vdc at the blade connector in the fuse box, same with the keep alive wire, red with a white trace wire at the blade connector in the fuse box.
 

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That stuff should all be going hot with the accessory relay and should be 0V with the key off. So there have to be two different issues here, one that the Acc Relay isn't turning on with the key and the other that power is leaking back into the circuit somewhere. I'd try to solve the relay first. The relay should have numbers inside the skirt, 1,2,3,5. Pull it and check voltage at the corresponding terminals. Either 3 or 5 should be hot all the time, that comes from the fat WHT wire on 2L at the fusebox. The other of 3 or 5 will be the relay output and should show no voltage with the relay pulled, but might be showing your 1.88V if there's a downstream leak into it. 1 and 2 are the relay coil terminals, one of them should get voltage in the Acc position from the WHT/BLU wire at the ignition switch. The other should ohm zero or near-zero to ground. Something there must be screwing up, so step one is to find out which terminal is causing the relay to not function.
 

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PS - I'd use a test light to check for the battery and acc-key signals, a voltmeter won't tell you if the circuits can carry power. If they'll light a bulb then there's good power there.
 

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Discussion Starter · #7 ·
Thanks! I’ll work on that tomorrow. I did swap all the relays in different locations, same results. ACC on, 1.88 vdc, ACC off, 0 vdc. I’ll rig up a test light if I can’t find the one in the garage. I have never had a relay go bad in any vehicle I’ve owned. I’m thinking maybe a bad fuse box but I have never had one go bad. There are two 2003/2004 X Terra’s in the local junk yard, maybe pay the yard a visit. I’m the second owner and the vehicle has not had any mods other than a new radio after the stock unit ate a CD. I’ll check for 12 vdc going into the fuse block, can’t hurt. Again, many thanks for the help
 

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Discussion Starter · #12 ·
I found the light, both of them. Kind of like an A -100 light used in aircraft, timing mags. Here we go.

The #3 is hot showing 2.0 volts

The #1 shows 0 volts until the key is turned on, then it shows 2.0 volts

The #2 is ground, key on or off. It shows about 7 ohms resistance key on, 1.0 ohms key off

The #5 shows nothing, key on or off.

I pulled all the connectors last night, all bright and shiny, put some dielectric grease on them and reassembled prior to the test

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As I was cleaning up and just for grins I tested voltage at #2 and #1 again. Now they both show 11.85 volts, #3 and #1 with the key on.

Totally confused here. I am reluctant about bolting all this back together until I figure out what is going on

Again, thanks for the help
 

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Discussion Starter · #14 ·
That is the plan. I’m thinking it may be something internal in the fuse block because I had the low voltage to the pins that connect to the wiring harness to the lighter and radio. The only input I see are the two large white wires that I assume send 12vdc to the fuse block. I have not figured how to pull those wires just yet. Many thanks again!
 

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Discussion Starter · #15 ·
Pulled the fuse box, nothing obvious at all. I'm going to put it on a 12vdc power supply in the shed and do some diagnostics. It has to be something internal in the fuse box.
 

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Discussion Starter · #16 ·
Went to the junk yard and pulled a fuse box off a 2004 X Terra, same fuse box, same part number. Installed it, checked voltage at the two white wires that input voltage to the fuse box. 12 VDC, on both wires. Pulled the ACC relay, using your test procedure, 12 VDC constant on #3, hot and 12 VDC to # 1key on. Buttoned up that side of the truck. Connected the radio to power, works fine. As I put the radio back into the slot in the dash the radio died, came back on and died again. I tested voltage......2.00 VDC to the radio ACC wire, nothing to the standby wire and 2.00 VDC to the cig lighter. Basically nothing changed with the new fuse box. As I understand it the two input wires just sends 12VDC to everything in the truck thru the connectors and wire looms protected by a fuse for each circuit. I can't think of any reason why nothing but 12 VDC should come out of the fuse box anywhere. I'm not buying two bad fuse boxes. As of ten min ago, no changes, 2.00 VDC to the radio ACC wire, nothing to the standby wire and 2.00 VDC to the cig lighter. I'm betting if i go back to the ACC relay Im going to get 2.0 VDC at #1 and #3. I'm thinking of running a 12 VDC line directly from the battery to the input of the radio and turn that radio just to see what happens.

Totally confused here.
 

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You're barking up the wrong tree with throwing parts at it. There's either an almost-broken wire or a connector that isn't connecting. The only way you'll find it is to trace the voltage drop back to wherever it goes from 12V to 2V. Since it changed when you messed with the fusebox, my first suspicion would be a weak or corroded terminal pin on one of those fat feed wires.
 

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Discussion Starter · #18 ·
I'll look tomorrow. The input terminals in each fuse box were shiny. I cleaned the surfaces of both fat feed wires and reassembled with dielectric grease. I'll trace the white feed wires to their source, clean, polish and lubricate tomorrow.

Head hurts..............-
 

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Discussion Starter · #20 ·
Recap. There is 12vdc on both white wires to the fuse box. Both terminals are bright, shiny, and coated with dielectric grease. There is 2.0 vdc at the #3 position at the ACC relay and 2.0 vdc when the key is turned on at the #1 position at the ACC relay. There are no connectors connected to the fuse box other than to make the ignition work. I have 2.0 vdc at the fuse that powers the accessories as well as the pin on the fuse box that sends 12 vdc to the hot wire for the radio. I'm going to trace both white wires from the fuse box that probably go to the engine bay fuse box, try to pull that box, clean and use dielectric grease on those terminals.

I'm baffled that I have 12vdc into the fuse box but only 2.0vdc output at certain terminals.

If that does not work I'll run 12vdc directly from the battery using a fairly healthy jumper to one terminal, then the other, then both on the fuse box and take readings.
 
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