An amusing electrical fault ...

[StuartG]

So yesterday evening I got the TR6 out of the garage to go to  Chiltern TR pub meet and noticed I had no fuel gauge reading, indicators, brake lights etc.  Went around with the multimeter and could find nothing obvious. So put the TR6 in the garage and took the trusty MX5 instead.

This morning went back into the garage to trace the fault and found it was a faulty fuse end cap. When I checked the fuse yesterday I checked I had 12V both sides of the fuse, which I had. By pushing the multimeter probe on the end cap I had obviously reconnected the fuse momentarily  fooling me into thinking the fuse was O K !

So simple fix which fooled me first time around, duh !

[Tim D.]

6 minutes ago, StuartG said:

So yesterday evening I got the TR6 out of the garage to go to  Chiltern TR pub meet and noticed I had no fuel gauge reading, indicators, brake lights etc.  Went around with the multimeter and could find nothing obvious. So put the TR6 in the garage and took the trusty MX5 instead.

This morning went back into the garage to trace the fault and found it was a faulty fuse end cap. When I checked the fuse yesterday I checked I had 12V both sides of the fuse, which I had. By pushing the multimeter probe on the end cap I had obviously reconnected the fuse momentarily  fooling me into thinking the fuse was O K !

So simple fix which fooled me first time around, duh !

Have had the same fault. Not sure fuses are the quality they used to be. 

[RobH]

Part of the problem is using a multimeter for fault-finding.  These draw so little current that the most tenuous of connections can read as being OK. Doing the same test with something that draws an appreciable current -  say a lamp - may well have shown the fault. 

[Hawk]

5 hours ago, Tim D. said:

Have had the same fault. Not sure fuses are the quality they used to be. 

 

And me.  I now carry a small jiffy bag of fuses just in case as that fuse seems to be the one that always blows. 

[StuartG]

Good point about using a test bulb rather than a multimeter...

[Mike C]

9 hours ago, Hawk said:

 

And me.  I now carry a small jiffy bag of fuses just in case as that fuse seems to be the one that always blows. 

Me too- the old glass fuses are getting hard to find in country garages, particularly in the high current ratings the TR originally used.

[John McCormack]

I don't trust glass fuses. I take them out whenever they are suspect and put a new one in. I carry a half a dozen in my touring bag. I will test the fuse later in the garage and if it is ok I put it in a zip lock bag marked used but ok.

 

[Mike C]

A piece of emery paper for cleaning contacts and earths is always useful in the glove box of any car with Lucas stamped on its components.

[StuartG]

Halfords do the 35A glass fuses

[RobH]

2 minutes ago, StuartG said:

Halfords do the 35A glass fuses

Beware.  Halfords and other suppliers may have glass fuses but they may not be the right type.  (There was a comprehensive article on this in TRaction a few issues ago).

The original Lucas fuse blows at the stated current - and that is what TR electrics are specified for.  to take the example of 35A, to be sure you are getting the right ones the label should say something like "17 Amps continuous, 35Amps blow".

The much more widely available (and near identical-looking)  SAE fuses will carry the stated current indefinitely without blowing and require twice that current to blow.  If the packaging just states one current they are likely the wrong ones.  

You can use the modern ones of course, if that is all you can get,  but you need to fit fuses of half the stated rating; i.e. if the TR book says 35A then you need to fit a 17A SAE fuse to get the same degree of protection for the wiring. 

[StuartG]

Thanks for that info Rob