Technical Uno Fire 1100 electrical nightmare.

[DigitalNomad]

Hey folks,

Just had a fiddle with the wires again, still no joy. Here is a summary of my not so good progress.

The symptoms:

I can start the car fine and drive around no worries. The heat gage works 100%.



When I turn on the head lights (on dim) the following happens:

1. The left front head lamp glows as usual.
2. The right hand head lamp is dead (appears dead, perhaps not enough juice).
3. The left hand rear indictor bulb glows permanently.
4. No other tail lights come on.
5. The right front side indicator light (mounted in the fender) is permanently lit.
6. The heat gage increases its reading to about half way through the scale.
7. It looks like some of the panel lights on the dashboard dimly lights up.
8. The handbrake-on light goes dead.
9. During this state if I want to use the indicators, nothing happens.

Now for the fun part:
If I pull out the choke so that its panel light comes on, all of the above symptoms vanish into thin air and everything works 100%.


This is what I have tried to do in the mean time:

1. I found, loosened and cleaned the earth mounting just under the battery, the one on the transmission, and the one just next to the right hand front headlamp as well as another one I found under the dashboard on the left hand side as well as another one I found near the left hand rear lights. They are all clean and tight.
2. When I noticed the effect of the choke light coming on, I located the choke switch, checked it and the two leads coming from it which disappears into a harness, up until where it goes into the harness, there was no visible damage to the wires and the switch is working 100%. The earth lead of this switch, apparently links up to the earth mounting under the dashboard on the left hand side, which I have cleaned and reattached.
3. Each of the rear light boxes are supplied with electricity via a mini harness which plugs into each one of them, I have unplugged and cleaned them as best as I could and under normal conditions, all the lights work properly, so they all get good power.

Preliminary deductions.
Perhaps when the choke switch flips on, it reconnects the “lost” circuits back to earth. It definitely has a positive effect on all of this, but I cant drive around with the choke on all the time. I checked what I believe to be the correct diagram and cant see that it is connected to other circuits though, it gets power from the ignition which goes through a bulb and the switch and back to earth.

This is really weird and any advice about how to proceed further would make my little Uno’s day.

Warm regards,

 

[DigitalNomad]

PS: Forgot to also mention that I unplugged both rear light boxes as well just in case I missed something inside them somehow), still not solved

 

[Ucof]

have you tried turning it off and on again..?


wait..
....its not a PC.
Sorry, I've been stuck in the office too long

 

[DigitalNomad]

have you tried turning it off and on again..?


wait..
....its not a PC.
Sorry, I've been stuck in the office too long

LOL take the rest of the day off

 

[DigitalNomad]

Hi there,

I think I am making progress. I did some basic tests with my DMM (digital multi meter) and made the following discovery which I think is significant.

1. With the car and all switches set to OFF, I connect the negative lead of the DMM to the negative terminal of the battery with a crock clip.
2. I took the plug off of the RH front headlight which is dead when I turn the light switch on. Anyways. It has 3 cables going into it, one +for the dim, one +for the brights and one -ground that connects to the earth mount a few cm away.
3. With everything switched off, I then placed the positive probe of the DMM on each of the three wires individually. Theoretically I suppose the reading on all 3 should be ZERO volts. There is a reading of about 0.07volt though.
4. I then put the headlight switch to ON and did the same test again. Theoretically the brights cable should read ZERO which it did, the dim cable should read close to battery volts (12.75V) and it reads 11.85V which is fine I suppose and the negative cable should read ZERO but it does NOT !!! It also reads 11.85V which is totally wrong!!!
5. The left hand front light is fine and does not display this symptom.

I think this is significant and that perhaps there is B+ shorting into circuits it should not be in. Even if I then take a Volt reading between the chasis and the negative batery terminal I get 11.85V. How on earth is this possible ?

 

[DigitalNomad]

Hi there,

UPDATE TIME:

I just had an idea and went out to test it. With all the lights and car and everything switched off, I just turned the ignition on untill the red lights on the dash lights up. With only the ignition in this position, I measure 9.8v between the battery negative terminal and the chasis and the earth mountings... also with all the lights turned off etc. the side indicator light on the RH front fender is lit permanently. Very weird.

Does this mean I should be looking for a short between the positive side or the ground side?

When I then turn the lights on, it worsens the reading...

 

[alexGS]

With only the ignition in this position, I measure 9.8v between the battery negative terminal and the chasis and the earth mountings... also with all the lights turned off etc. the side indicator light on the RH front fender is lit permanently. Very weird.

I assume that you are leaving the negative cable connected to the battery at all times, in which case there should of course be no voltage difference between the terminal and the chassis.

I think the only possible explanation is that your battery negative terminal connection is bad. The circuits are earthing here, there, and everywhere (e.g. through the side indicator light, through the headight). Things probably change when the engine is running, because then the alternator provides an earth back to the chassis (via the engine/gearbox and its earth connection).

Wirebrush the battery terminals thoroughly and try your measurement again.

-Alex

 

[DigitalNomad]

Hi Alex,

Yes, both battery cables are secured to the battery during that test with only the ignition turned on. When like this, I measure 9.8v I will go clean the terminals etc. in a few moments and retest. It does not improve when the engine is running.

I did another test last night which went like this. I disconnected the battery positive lead. Connected the negative side of my DMM to the negative battery terminal. The positive lead of the DMM I took a resistance reading on the two live wires that goes to the RH headlight. The idea here is that there should be no resistance measurment possible as these wires should be dead and not at all connected to the earth. Yet when I measure on the low beam live wire, there is a ohm reading, on the brights lead an "open line" which is correct and a slight reading on the earth lead which is fine. Could you confirm as well that this then implies a "short to ground" between the dim light circuit and the ground. The same phenomenon is atained on the LH headlight as well.

Just thought I'd pop that in here as well. At the moment i am just testing in random circles, I need to get more organized and systematic. Will try to take things from one side today, not sure where to start though, but will try to make sense of it all still.

Thanks for your posts

 

[DigitalNomad]

Hi Alex, me again. Just cleaned the terminals, lugs the whole works, looks brand spanking new. Unfortunately no change in the problem.

Will try more tests. Thought of starting with the wires from the ignition, figuring out what they are and when i turn the ignition, which one's become hot, follow them around a bit and perhaps find a short to ground. Not sure if this is viable, will give it a fair shot though

Any other idias you guys might have, please let me know, I'm going grey and it's not from age

Regards,