Power to "Dome" circuit only when "On" (1 Viewer)

[MadMace]

Truck is a 1986 FJ60. My dome light and carb cooling fan are not working. At the fuse box, there is no power to the "Dome" circuit when the ignition is in the "Off" and "Acc" position. Once the key is moved to the "On" position (truck does not have to be running), I get power (12V) to the "Dome" circuit and the dome light.

I have searched different threads and tried everything I know to try. I've cleaned the common ground on the 3rd cross member, taken apart and cleaned the "Cooling Fan" relay, changed out all the fuses. Any ideas where I should look next?

Thank you in advance for the help and guidance.

 

[mattressking]

Truck is a 1986 FJ60. My dome light and carb cooling fan are not working. At the fuse box, there is no power to the "Dome" circuit when the ignition is in the "Off" and "Acc" position. Once the key is moved to the "On" position (truck does not have to be running), I get power (12V) to the "Dome" circuit and the dome light.

I have searched different threads and tried everything I know to try. I've cleaned the common ground on the 3rd cross member, taken apart and cleaned the "Cooling Fan" relay, changed out all the fuses. Any ideas where I should look next?

Thank you in advance for the help and guidance.

Power for the dome comes directly from battery through fusible link via the White wire. It comes into the 7.5A dome fuse. If you do not have +12V @ fuse (with fuse removed) on either pole, you need to chase the wiring. The White wire also feeds a few others things such as headlight washer, heater fans, and other lighting circuits, so I doubt it doesn't have power, but weirder things have happened. Try playing with the voltmeter, sometimes corrosion can kill the reading. If you find you have power coming into fusebox for the Dome circuit, then move to inspecting lamp.

The carb fan is pretty common not to work. It uses a ground thermistor located under rear section of intake manifold to open and close grounds based on engine temperature. Locate the wire under rear section of manifold off the pcv hardline bracket. If its dangling, not there, or something else, it just needs to be grounded, test by grounding and see if it starts spinning. If grounding this wire does nothing when you turn ignition switch on and off, then the timer, other wiring, or fan itself is an issue.

 

[MadMace]

Power for the dome comes directly from battery through fusible link via the White wire. It comes into the 7.5A dome fuse. If you do not have +12V @ fuse (with fuse removed) on either pole, you need to chase the wiring. The White wire also feeds a few others things such as headlight washer, heater fans, and other lighting circuits, so I doubt it doesn't have power, but weirder things have happened. Try playing with the voltmeter, sometimes corrosion can kill the reading. If you find you have power coming into fusebox for the Dome circuit, then move to inspecting lamp.

The carb fan is pretty common not to work. It uses a ground thermistor located under rear section of intake manifold to open and close grounds based on engine temperature. Locate the wire under rear section of manifold off the pcv hardline bracket. If its dangling, not there, or something else, it just needs to be grounded, test by grounding and see if it starts spinning. If grounding this wire does nothing when you turn ignition switch on and off, then the timer, other wiring, or fan itself is an issue.

Thank you for the info. What I have found interesting is that there is power to the dome circuit at the fuse box when the key is turned to the "On" position, but no power when in the "Off" position. I find that odd considering it should have constant power. Is there any reason that comes to mind as to why it is now only getting power in the "On" position?

Regarding the carb fan, I forgot an important detail. My truck was desmogged by a PO. When this was done, the temp sensor on the intake for the carb fan was removed. I found the wire that went to the temp sensor just dangling in the engine bay so I grounded it to the body of the carb fan. Unfortunately this did not change anything.

In reading the schematic, the white wire that feeds the "Dome" circuit is "C". The only things not working that come off that fusible link are the dome and cargo lights and the carb fan.

 

[OSS]

Sounds like the DOME fuse circuit has been tampered with by the PO.
The DOME fuse should have live 12 volts regardless of key position.
The manifold/carb fan normally is protected through the DOME fuse and it needs to have power when the engine is off, key out and you gone as it cools down the carb when you walk away - or that's how it's supposed to work.

If I wanted to fix the problem, I'd unscrew the two bolts holding the fuse panel in and push out the whole panel and take a look behind it to see if there's any modifications to the wiring. If it looked unmolested, I'd start snooping around for suspicious splices in the harness.

 

[MadMace]

Sounds like the DOME fuse circuit has been tampered with by the PO.
The DOME fuse should have live 12 volts regardless of key position.
The manifold/carb fan normally is protected through the DOME fuse and it needs to have power when the engine is off, key out and you gone as it cools down the carb when you walk away - or that's how it's supposed to work.

If I wanted to fix the problem, I'd unscrew the two bolts holding the fuse panel in and push out the whole panel and take a look behind it to see if there's any modifications to the wiring. If it looked unmolested, I'd start snooping around for suspicious splices in the harness.

When I found that there was power to the "Dome" circuit with the key "On", I figured I would find that a PO had messed with the fuse panel. I removed those bolts and checked the back of the fuse panel and to my surprise, it was unmolested--all the wires were in place and did not look like they had been messed with. The wires coming out of the loom into the back of the panel also look like they hadn't been messed with.

I guess it it time to start looking for splices. I have not yet looked at the inspection light and it's wires--that will be next. It is just weird to me that it is getting power with the key in the "On" position but not in the "Off" position. I might be ignorant in assuming this, but that tells me that the connection from the battery to the fuse panel is intact and that it is a connection after the fuse panel that I should be looking at that.

 

[OSS]

All power to everything except the starter gets routed through the fusible link at the battery. The link has three wires. Each wire in the link fuses a certain circuit. Toyota designates the three main fusible linked circuits as "A", "B", and "C" in their wiring diagram at the back of the Chassis & Body Service Manual.
There's also a "D" and "E"
circuit that branches off from the ignition switch.
The DOME light circuit is supposed to get power directly from the "B" fusible link circuit - not through the ignition switch.

I'd inspect the fusible link first to make sure it's ok - then (once again) look for molested wires that have been spliced

 

[MadMace]

Ahhhh, now that is interesting, thank you very much for that image. The only wire schematic that I have been able to track down is for a 1983 FJ60 (from coolerman's website). That schematic shows the dome circuit coming off of "C" so I have focused on that fusible link wire. I have not yet looked into the link that corresponds to "B". Now I cannot wait to get home from work to check this out.

Is there a place that I can download a wire schematic that would be correct for a 1986 FJ60 because it clearly looks like I am looking at the wrong schematic.

 

[OSS]

See attached

 

[MadMace]

See attached

Thank you!

 

[MadMace]

For the life of he I cannot figure out how to get the relay block off, I only see one screw. I don't want to break it. Can somebody please tell me how to get the other side off.

 

[OSS]

I think if you remove that bolt, the relay mounting board slides back/forward a bit to release it from the rear bolt held in a slot? I don't remember exactly.

 

[MadMace]

I think if you remove that bolt, the relay mounting board slides back/forward a bit to release it from the rear bolt held in a slot? I don't remember exactly.

You are correct, it slides towards the firewall and pops off after that one bolt is removed.

 

[MadMace]

I have spent the whole weekend trying to figure this out. I have had taken the glove box out, removed the center bezel/panel (where the AC control, ash tray, etc are), gauge cluster, and relay block looking for wire splices, etc that might be the culprit. I found nothing--harness was all intact. The PO told me that they had installed a kill switch so I figured I'd look into the more as a possible cause.

I removed the DS kick panel and the kill switch installed by the PO has a black jumper wire from the 20A wiper slot on the fuse box spliced into the B-Y wire coming from the Emissions control computer--I have found that this wire controls the Idle Fuel Solenoid (picture below). Specifically, when the switch is "On" the idle solenoid activates when the ignition is moved to the "On" position. This also activates all wires in the fuse panel that are white--specifically the Stop, Dome, and C/B Heater--all work normally. If the switch is turned "Off" OR if the key is moved to the "Off" position, power is cut to these.

There is no continuity between the white fusible link wire at the +battery terminal and the white wires at the fuse panel when the switch is "Off" OR the ignition is "Off" but if the key is "On" and the switch is "On", continuity is established.

I have tested the relays and they are all working fine and have normal resistance as outlined in the FSM.

If I remove the jumper wire from the B-Y wires and re-attach the B-Y wires together, there is no power to the idle solenoid or white wires with the key in any position.

So, I really need help as I am stuck. In looking at schematics, it looks like it could possibly be the voltage regulator on the alternator. Maybe the Emission's Control Computer? How about the ignition switch itself--I noticed that I can remove the key from the ignition even if it id in the "On" or "Acc" position, which I am sure is not normal. Any help is very much appreciated.

 

[MadMace]

AAAAAAND this would be the problem:

It was hiding in this:

I feel a little silly that it took me as long to figure this out as it did--although, in my defense, I just bought the truck the Saturday before last. I have looked and re-looked at the wiring schematic so many times I've been having nightmares about circuits and fuses and relays. I looked over as much of the harness as I could see--I found ways to contort and twist my body under the dash that I didn't think possible to see if there were any splices/molestations to the harness by a PO. I kept coming up with nothing. Today, I go to the point that I started checking any part of the harness that did not look like it was wrapped in factory tape. The split loom tubing to the alternator was the last part of the harness that I looked at tonight.

I did not look at it sooner because the split loom tubing was nicely wrapped in tape and it did not even occur to me that some jackass would cut the wires going to/from the alternator when they can be easily disconnected and reconnected. Well, as the 1st picture shows, I was clearly wrong. Honestly, s***ty stuff like this annoys me beyond belief. It's not the cutting and splicing so much as the absolute half-ass, don't give-a-s*** way it's done. The white wire with the blue butt splice was only attached to one end--the other end had worked itself loose and therefore had no connection to the harness.

Once it was found and a jumper wire placed between the 2 severed ends, all those circuits came to life. This all started because my carb fan wasn't coming on when the engine was turned off--it now runs when the ignition is turned off.

It was a good night!!

 

[MadMace]

Is it okay to use braided/stranded wire that I can purchase at home depot to repair these damaged wires as long as it is the right gauge or do I need to buy wire that is intended for automobiles? Home depot does have 10 and 12 gauge braided wire with white insulation that is a pretty good match.

 

[Dr. John]

The wire you describe is fine.

 

[MadMace]

The wire you describe is fine.

Thank you.