456mgt electrical gremlin: help needed

the battery must have been damaged in the recent issues with the alternator. so it died and would no longer take a charge. i jump started it, and took it to the usual mechanic, and he swapped it out.
since i picked the car back up i noticed a few things had stopped working....the fuel filler flap button will no longer activate the door, the trunk release also does not release the trunk, the interior lights will not come on, the vanity mirror lights do not light, the circle of light around the ignition switch does not light up. so far these are the only things i have noticed that do not work, but these need to be brought back of course.
i turned off the battery switch, and then got into the fuse box to check things out. i inspected every one of the colored plastic fuses in the front row - all fine. i then took out the quare fuse S since that is key related but i cannot see how you are supposed to tell if its blown or not. then i got into the other fuse box on the lower right side on the firewall side of the fuse area, and checked those out - all fine. then i popped the fuses B and C out from the fuse box in the engine bay near the battery cutoff switch - also fine.

so, after checking every fuse i could, and finding them all unblown, i am stumped....i suppose there are solenoids running the trunk and fuel filler cap releases (where are those anyway?) - but the interior lights dont have that issue....

so, i would greatly appreciate any and all help on this subject before i send it back to the mechanic (and he racks up hours of labor charges rummaging around).

 

If a fuse conducts current, it's not blown.

A basic multimeter is pretty much needed to trace wiring.

You can check ATC fuses in place by probing the two open spots with a voltmeter. If it's exactly 0.0 volts between the two points, then the fuse is good. If it's 12v then it's blown. If it's a wandering number of millivolts, then the circuit isn't active, but the fuse is likely blown.
(A dead short -- a good fuse -- will always read 0 volts.)

If none of the fuses are bad, you might look for want connectors the shop might have undone while swapping the battery and/or alternator.

 

what connectors are you referring to? if the main connectors are on since the car runs, then what other connectors are there??

 

There are scores of connectors all over the car.
The fuse panel(s) might have several. (I don't have details on a 456.)
A shop might disconnect any that might be "in the way".

With a wiring diagram, you might correlate the inop functions with the wires through various connectors. Particularly fuse panel connectors.

Otherwise, you have to trace the voltage.

Not a task for someone not electrically inclined.

If this all started from the shop, then they ought to make it right.

 

The 456 battery is in the passenger side rear of the engine and no where near anything that needs to be disconnected. It does sound like a fuse even though I realize you have inspected them all. Did you test them or just look?

 

i just looked. how would i test them?

 

I find an inexpensive 12V test light to work best for me as a simple go/no-go tool for automotive electrical circuits. Clip the test-probe wire to ground, turn ignition key on. Then touch the probe to both ends of each fuse connector with fuses all in place. The probe must light when touching both ends of the fuse connectors, thereby proving not only that the fuse is ok but that voltage is reaching the fuse.

A voltmeter can be used but you have to look at it, whereas the test light provides indication of voltage by illuminating the area and you can concentrate your focus on what you are touching, not removing your eyes to view the meter. Plus, exact readings are immaterial making digital meters less desireable than older analog style, but very few mechanics have retained their superior analog meters in the interest of new age devices.

 

My cheap multimeter will beep in "continuity" mode.

To have 12v on the fuse, the related circuit has to be active.
E.g. the headlight fuses might not have voltage on them when the headlights are off.
But you can test continuity across the ATC fuses whether they're active or not.

Most ATC fuses have test points on the back, so you don't have to remove them.
You can check 12v to ground on both sides with a test light, or you can test continuity across the fuse.
Image Unavailable, Please Login

 

It is very likely that when you reconnect the battery the items will start working again. If they don't try arming and disarming the alarm a few times and this might fix the problem.... If not you need to ck fuse #13 in the main fuse box and fuse #8 in the secondary fuse box in the pass floor. Good luck! Let me know if I can help....

SCLJA
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login
Image Unavailable, Please Login

 

ok guys, i got myself one of those meters. then i checked every single fuse again.
quite a number of them do not light up the meter.....but when i changed those ones out, the new ones did not light up either. i did this with all of the ones that did not light, then i did it with some that did light just to make a control check.
so, i have several fuses that do not light, but wont light even when replaced. i guess this means that somehow power is not getting to those fuses at all.

i checked the fuses at the back of the footwell fuse box (covered by the black box), and they all lit up.
i checked the fuses near the battery under the hood, and they all lit up too.

so now what??

 

some fuses are on a constant circuit (all the ones that lit up) and some are on ignition (when the key is all the way on)

sclja

 

And some fuses might not be "on" unless the function that they serve (e.g., headlights on some models) are "on". If you can get access to an electronic copy of the wiring diagram for your model, I'd be glad to cast an eyeball over it and see if a simple flaw might be a logical cause of your (not simple) symptoms.

 

Perhaps a few driving cycles are needed to reset the on board computer parameters.

It often happens when all power is dumped from the electrical system. Just as a PC needs to be rebooted occasionally.

 

Sounds like most of those functions would work without the key. Theyn are likely all on the same circuit. Perhaps a fusible link is blown for that circuit. Perhaps the battery was connected backwards or the over worked/malfunctioning alternator overheated or blew a fusible link. Is the alternator now charging since it was replaced?

 

i will be checking steve's suggestions this morning.

i have turned the battery off and on several times since these issues were noticed, and the result is the same.
what is a 'fusible link' and where is located?
the alternator seems to be working since the battery replacement. the alternator was replaced in modena in sep (along with a full 20k service etc). everything was working fine prior to the battery dying and being replaced.

 

ok, i rechecked the battery terminals, and cut-off switch. all seem to be ok and tight.

then i checked all the fuses again with no key in the ignition, key in the on position, and engine running. some fuses light under different circumstances as some of you thought.

the consistent failures are fuses 9-15. these 7 fuses do not light under any setting. the fuses themselves are not faulty since i swapped them out and they still dont light.

i switched off the cut-off switch again and tried from the start - same result.

and here is the other puzzling info....fuses 9-15 comprise all sorts of different functions, but 9-12 functions work despite the fuses not lighting. it is really only the interior lights, the trunk release, and the fuel filler flap release, that do not work. and i can only identify fuse 13 as being the interior lights fuse. what are the trunk and filler flap release fuses?

now i am officially frustrated !!

 

Still sounds very much like a single circuit is out and problem with a fuse or perhaps a connection problem. They are all light draw "accessory" type circuits and sound like they may well all be on the one.

I'd suggest picking what you feel is the most easily accessed service that isn't working and trace back to source.

Annoying and frustrating but amost certainly curable with patience. Good luck!

P.s. check again in close proximity to any areas of recent work. A screw holding an inspection panel in place may have pierced a wire behind or a connection block pulled apart in the process of the work.

 

Aside from fuse protection a fusible link is a device installed in wiring that is designed to burn out before the wiring melts in the case of an electrical overload. Not sure if this circuit would have one. They look like a bulge in the wiring. I really does sound like the main power source for this single circuit is out. You will need a wiring diagram to trace it. Power will come to that circuit from the battery, main positive connection at the alternator, I would guess. Look at the connections from the positive side of the battery and alternator. Without a wiring diagram you are shooting in the dark.

You can check that your battery is charging with your new meter. First, with the car off, connect the meter leads to the pos and neg of the battery. You should show somewhere north of 12 volts. Then start the car and do the same-you should show somewhere over 14 volts-if you can rev the car a bit with the meter connected and if it doesn't show 14 immediately at idle reving it a bit should. PB

 

As said, a test light will only light up on an active circuit.

If the fuse is on an inactive circuit, like the headlights, there won't be any voltage to light up the test light.

You can get an actual multimeter for about $5 online or for under $20 at a local store (Radio Shack or local household supply store).
You can test continuity across ATO/ATC fuses using the test points on the back. That would work whether the circuit is active or not.

You need a wiring diagram to determine which function comes off which fuse.

Think of an electrical circuit like plumbing. Current comes flowing out of the battery, flows through the circuit, and drains back to the battery. Interrupt that circuit anywhere, and it all stops flowing.

So you have to methodically trace the circuit path from the battery to the load device and back.
That's a lot easier with a circuit diagram, although the sheets Scott posted could help.

 

Check all grounds. Bad grounds can cause such anomalies!

 

Poor contrast and low resolution make the posted images impossible for my bad eye to read. ... is there a public publication or that document?

Good job examining all fuses to ensure they all had either voltage on both sides or no voltage at all on either side. Great necessary first step. While it's still irritating for the moment that you have identified several circuits which should work but aren't because those circuits get no voltage, hang in there... those specific circuits get examined next.

If you can read those drawings to coorelate and learn if any bad circuits on your list were proven to link to one of those 'dead or unlit' fuses which you just identified. Any fuse that didn't light up and not receiving proper voltage get focus. By examination of the drawings posted above, find or coorelate one (or more) of the components listed as not working, to the fuses which didn't light up during that test. And report back.

I see the non-function list include:
1 fuel filler flap button will no longer activate the door
2 trunk release does not release the trunk
3 interior lights will not come on
4 vanity mirror lights do not light
5 circle of light around the ignition switch does not light up
6 so far these are the only things

Is anyone with ability to read the fuse list find any of these 5 items identified to a fuse?

 

Fuse 13 (7.5A) under passenger side footrest seems the most likely - "Interior lights, instrument and licence plate lights"

 

- guess : earthing.

.

 

Exact same set of symptoms... Add that my clock stopped working too... I'm betting yours did as well and you just didn't notice. What did it end up being? Which circuit or fuse?