MINI BLADE FUSES

brorabongo · Post by **brorabongo** » Wed Jan 23, 2008 10:19 pm

I'm I right in saying that the fuses can be tested in situ, with a continuity meter?

There seems to be a very small patch of exposed metal, at the top of each pin.

My meters fubar, so can not try it out to see if so.

BongoMTBer · Post by **BongoMTBer** » Wed Jan 23, 2008 11:07 pm

Just slave them into another circuit that you know that works

roosteruk · Post by **roosteruk** » Thu Jan 24, 2008 8:44 am

The only way to test correctly, is to remove them.

stringman · Post by **stringman** » Thu Jan 24, 2008 10:00 am

You can test them in situ with a volt meter. If you have 12 volts both sides the fuse is ok

roosteruk · Post by **roosteruk** » Thu Jan 24, 2008 6:11 pm

stringman wrote:You can test them in situ with a volt meter. If you have 12 volts both sides the fuse is ok

Not if you have fault with a floating current or induced from a high capacitance cable.

Even testing for 12volts like this is incorrect.
You need to put the voltage under load, as it may have well lost the current to induce the voltage.

Best way to test a fuse. Take it out and test continuity across the two contacts. Do not hold the contacts or probes of the tester with bare skin, as the salt in your skin/sweat can provide continuity.

stringman · Post by **stringman** » Fri Jan 25, 2008 10:44 am

I agree but a quick test by the roadside for a blown fuse can be done with a test light. Removing fuses on a relatively primitive electrical system as fitted to a Bongo should not be a problem and is actually a good idea as a problem I have experienced with blade fuses is that they oxidise which causes issues. Breaking and making the connection can clean this. I replaced all the fuses in my Bongo when I got it for this reason.
However, be careful removing fuses on newer vehicles with SRS systems, CAN BUS wiring, ABS etc especially with the ignition switched on as this can cause warning lights to activate resulting in a costly trip to the dealership to have these reset

brorabongo · Post by **brorabongo** » Sun Jan 27, 2008 12:17 am

I have tested, with a meter, and have found that you can test the mini blade fuse, whilst still in situ by testing for continuity across the two very small patchs of metal, one on either side of the printed "amp" value. This of course wont help if the original fault is due to a bad connection, with the blades as said by Stringman.

Now where shall I buy myself another meter.

roosteruk · Post by **roosteruk** » Sun Jan 27, 2008 8:38 pm

brorabongo wrote:and have found that you can test the mini blade fuse, whilst still in situ by testing for continuity across the two very small patchs of metal

If the fuse has blown, you can still get continuity if the rest of the circuit is uninterupted!

See the simple circuit below.

Pretend the fuse has blown....OK? The switch is closed and the lamp is not blown.
Putting a probe on one side of the blown fuse, with the switch in the on position and presuming the lamp has not blown, the meter will show continuity as it will find its path through the battery, via the positive, the negative, through the chassis, through the lamp, through the switch and then to the probe on the other side of the blown fuse.

Your initial question

I'm I right in saying that the fuses can be tested in situ, with a continuity meter?

I have tried to answer twice.
The answer is , NO! you are not right in saying that the fuses can be tested in situ, with a continuity meter. The only way to correctly test the continuity of a fuse, is to remove it completely.

brorabongo · Post by **brorabongo** » Sun Jan 27, 2008 9:26 pm

Thanks rooster

I do understand what your saying, as I test continuity on Components in domestic appliances regularly, by first making sure the appliance is unplugged at the wall,(goes without saying) and then disconnecting the plug/wires going to the Component being tested, for the same reason as you have stated above.

Just wanted to know if they could be tested from above, and they can. What I did not know was, if the two tiny patches of metal on top of the fuse were bare, or did they have a clear cover insulating it.

Why would you design the fuse with these patches? Thats what made me think it would be for ease of testing?

Hope you can all make sence of my ramblings.

All the best.

roosteruk · Post by **roosteruk** » Mon Jan 28, 2008 12:17 am

The bare patches in the fuse, are for testing for voltage, yes, but not continuity.
As I have tried to explain, with diagram, continuity can come from the circuit if you are not careful.

Cheers

Karl