Generator Failure?

[ola]

Bleeno, you really make me laugh but what

[mumof4]

If the cable is faulty..which i believe it to be...the more you keep turning the engine on..the more chance there is of that fuse going poof again.You need to replace it then do all your tests.

 

Its simple...why replace just the fuse when what caused the fuse to go poof was the cable chucking loadsa heat out soo stands to reason to replace the cable then see how the battery and alt do.

[insider]

don't think it'll be that much fun when it catches fire from 300AMPS of DC running through it. Still if you'd rather measure DC with an oscilloscope then go ahead.

 

The inputs to an oscilloscope are very high impedance and, therefore, the current would be negligible. Oscilloscopes measure voltage waveforms.

[ola]

Bleeno: Oh, I thought I had an AC generator with a diodpacket to make it a DC outlet.

Are any capacitors? If not there would be small waves on the DC as the diodes

leads after each other to make the DC. Even with capacitors it

[Smilge]

Bleeno, you really make me laugh but what

[tim-spam]

From what I've read so far, you have a bad contact somewhere in the cable from the alternator to the primary fuse box. This lead to excessive heat build-up and the contact and fuse to melt. Your alternator and battery seem to be OK, so I would just replace the cable - a decent auto-electrician should be able to make one up for you, or you could try a VW garage.

 

If you do this, you should be fine.

[Smilge]

don't think it'll be that much fun when it catches fire from 300AMPS of DC running through it. Still if you'd rather measure DC with an oscilloscope then go ahead.

 

The inputs to an oscilloscope are very high impedance and, therefore, the current would be negligible. Oscilloscopes measure voltage waveforms.

 

Yes but they also measure DC ..... how do you measure DC levels in BASIC transistor circuits whilst showing the waveform ....tut!

[seatkid]

EVERYONE AGREE???

No... :P

[Smilge]

How did I guess DOCTOR Seatkid would say no? ........ :) :P Well I'm a consultant ...now get back down to engineering and help scotty!

[caiss4]

To Bleeno, I agree with your description of what the 'battery' light means. My point was that ola stated it goes out before the engine is started and the alternator is 'self-exciting' (it'll go blind :P )

[mumof4]

Crumbs at least 3 of us agree to replace the cable first THEN see what happens!..the cable is at fault here..My battery was fine when mine went..even when the second time it went the bushes? in the alt were burnt out!..Silver Calcium batteries are a lot more robust then lead acid ones.

 

since i didnt understand a word you said Bleeno....i'll pass on that vote :P

 

 

 

P.S.

 

just replace the cable..and i reckon it will allllllllll be fine.

[seatkid]

..Silver Calcium batteries are a lot more robust then lead acid ones.

 

Can I now state for the record.......

 

"Silver Calcium" batteries are in fact lead acid batteries.........

 

Oscilloscopes measure voltage not current........

 

This year is not a leap year..........

 

I could continue....... :P

[mumof4]

I need to correct myself here..it was the diode pack that was burnt out in my alt that went..

 

 

http://www.fordgalaxy.org.uk/ford/index.ph...l=fuse+feed+box

 

doing a search..this is a common fault ....a worrying one i think....there are quite a few of us this has happened to.

[Smilge]

..Silver Calcium batteries are a lot more robust then lead acid ones.

 

Can I now state for the record.......

 

"Silver Calcium" batteries are in fact lead acid batteries.........

 

Oscilloscopes measure voltage not current........

 

I could continue....... :P

 

Umm ..... I didn't say they measured current .... I said "Don't risk the scope on high current DC" which meant, don't measure DC with a high current level.

 

and why do they call them Silver Calcium then ...... I'm lost now? :)

[ola]

Good to have you as consultant, Bleeno, In a devlish moment I

thought it would be exremely cunning to use an oscilloscope because

in my world I would be able to see not only the small pulses on the DC

but also if a diode was failing but if you claim that there is a clean DC...

[mumof4]

Hmmm........

 

In this thread...it has a post about the voltage of calcium batteries

 

http://www.fordgalaxy.org.uk/ford/index.ph...l=fuse+feed+box

[Smilge]

Good to have you as consultant, Bleeno, In a devlish moment I

thought it would be exremely cunning to use an oscilloscope because

in my world I would be able to see not only the small pulses on the DC

but also if a diode was failing but if you claim that there is a clean DC...

 

In your world ola ........ ITS ALIVE ITS ALIVE ...... lol ......Now Dr Frankensteen ..... They're filthy diodes! When it comes to charging a battery you dont need lovely smoothed stabilised DC ..... just select AC on your meter and measure the ripple voltage coming from the alternator. Disgusting!

[mumof4]

But if he just replaces the cable...everything may be ok..then he can do alll this ac/dc stuff cant he??

[ola]

Argh, thanks Bleeno, you agreee that it

[insider]

Umm ..... I didn't say they measured current .... I said "Don't risk the scope on high current DC" which meant, don't measure DC with a high current level.

 

I think you're confusing your currents and voltages!

Yes, the voltage will be DC (not AC) so the waveform will be a flat line, the vertical position of this line indicating the actual DC voltage.

Yes, you don't gain anything by using an oscilloscope instead of a multimeter to measure DC.

No, you won't damage the oscilloscope because there won't be a high DC current. If the input impedance of the oscilloscope is 1Mohm (conservative) then the current at 14v would be 14uA! (Ohm's law I=V/R)

[mumof4]

Hmmmm..

 

Sooo..having been lost a few posts ago on AC/DC......is this "High Voltage" which makes the cable a "live Wire" which in turn caused a "Meltdown" with a "Flick of The Switch" or have i got it "All Screwed Up"??

[insider]

or have i got it "All Screwed Up"??

 

Yes, it's the current that generates the heat, not the voltage, which in this case is low anyway.

I don't recommend it, but if you put a spanner across the terminals of a car battery, the voltage will be low (12v) but the current will be very high and the spanner will melt, but possibly not before the battery has destroyed itself!

 

Ohm's law again I = V/R.

V=12v, the resistance of the spanner ® is very low therefore the current (I) is very high.

 

AC = alternating current and the voltage is also alternating while the resistance is constant.

DC = direct current and the voltage is also constant while the resistance is constant.

[seatkid]

no...."All Screwed Up" is what most people call me.... :)

 

All car batteries are Lead-Acid. In recent years all car batteries have switched to using calcium instead of antimony for reasons of being maintenance free

 

Lead Calcium Batteries

 

Lead acid batteries with electrodes modified by the addition of Calcium providing the following advantages:

 

* More resistant to corrosion, overcharging, gassing, water usage, and self-discharge, all of which shorten battery life.

* Larger electrolyte reserve area above the plates.

* Higher Cold Cranking Amp ratings.

* Little or No maintenance.

 

Lead Antimony Batteries

 

Lead acid batteries with electrodes modified by the addition of Antimony providing the following advantages:

 

* Improved mechanical strength of electrodes - important for EV and deep discharge applications

* Reduced internal heat and water loss.

* Longer service life than Calcium batteries.

* Easier to recharge when completely discharged.

* Lower cost.

 

Lead Antimony batteries have a higher self discharge rate of 2% to 10% per week compared with the 1% to 5% per month for Lead Calcium batteries.

 

I don't think theres any hazard in using an oscilloscope anywhere on a vehicle (except ht/spark plug leads!). The obvious thing to avoid with any measuring device is not short the leads! I think Bleeno has good intentions but perhaps is not putting his point across very well. It doesn't help when the the term DC (Direct Current) has really nothing to do with current (in this context anyway).

 

The output of an alternator is a 3 phase bridge rectifier output. Depending on cable resistance,battery impedance,circuit capacitance and load, you will get a little ripple on the "live" wire.

[Bigjeeze]

So.....Does he just put in a new wire? :)

[seatkid]

Yes.

 

And when that gets warm too he changes the battery. :)