Cannot get ammeter to work.

[SpitfireGeorge]

Thanks Dave, that's a point worth noting.

Cheers Brett

[Wagger]

I am chipping in late again, however, testing a dynamo is relatively easy, but you need a multimeter set to about 50 volt range. (or an auto ranging one). They are reasonably priced.

Do as follows:-

Disconnect both wires from the dynamo and temporarily connect the two terminals on the dynamo together. Measure the voltage between this temporary connection and the body of the dynamo with the engine ticking over. It should be about 12 to 15 volts. This will be +ve or -ve depending upon whether you have postive or negative earth.

Increase the revs slightly and the voltage should rise. Do not rev too high as it could top 50 volts.

This proves that the dynamo is good.

Now connect the dynamo up again and connect the multimeter directly to the battery. If you can start the car using the under bonnet solenoid button, watch the meter as you press the start solenoid. It will dip to 10 volts or below and then rise when the engine starts and you release the button.

Now, if you rev the engine at between 2000 and 3000 rpm, the meter should read between 13 and 14 volts. Even if you rev it higher, the voltage should remain within the same band. If it does not rise, or rises above 15 volts, then your regulator box needs adjusting.

I agree with most now in that a dashboard voltmeter is a better option than an ammeter. I am a retired Electrical and Electronic Engineer and have had many problems using wired in ammeters, not just in cars. They cause measurement errors, voltage drop and fires when the terminals work loose. The connections heat and cool in use so connections always work loose and vibration in a car makes this more likely.

Voltmeters do not carry working current so do not warm and cool at anything like the same rate.

I always use current clamps now for measuring current because they require no disconnection. AC/DC versions cost about £80.

 

 

 

 

 

[daverclasper]

4 hours ago, Wagger said:

Disconnect both wires from the dynamo and temporarily connect the two terminals on the dynamo together. Measure the voltage between this temporary connection and the body of the dynamo with the engine ticking over. It should be about 12 to 15 volts. This will be +ve or -ve depending upon whether you have postive or negative earth.

 

This was what threw me, as I could only get 5-6 volts at idle, on the three different dynamos, so assumed they were duff.

This part of the test, has always worked ok for you then Wagger? 

[daverclasper]

23 hours ago, johny said:

oh dear Dave and I thought the procedure for dynamo testing was much easier than that for the regulator😆 Maybe yours had lost their residual magnetism and needed flashing? 

I flashed all three. Charging fine after I changed voltage regulator

[Wagger]

1 hour ago, daverclasper said:

This was what threw me, as I could only get 5-6 volts at idle, on the three different dynamos, so assumed they were duff.

This part of the test, has always worked ok for you then Wagger? 

Maybe tick over is too slow. It should be 12 to 15 volts at 1000 rpm. That test always showed a completely duff dynamo for me.

Another test is to disconnect the fan belt and connections, connect the two terminals together and use jump leads to this connection and the casing connecting to the battery. It should run smoothly as a motor and be powerful. If it hunts or chogs, it has a poor armature. Need to use the correct polarity, or you will reverse the charge voltage.

 

[daverclasper]

2 hours ago, Wagger said:

Maybe tick over is too slow. It should be 12 to 15 volts at 1000 rpm. That test always showed a completely duff dynamo for me.

 

Maybe. I seem to remember the info was something like "there is no point, in increasing the rpm from idle", for this part of the test. I was aware of the "motor the dynamo" test, though didn't try this. The Club Triumph forum guys, were also surprised, at the results I was getting, though I don't think they had personal experience of this test 

[Wagger]

31 minutes ago, daverclasper said:

Maybe. I seem to remember the info was something like "there is no point, in increasing the rpm from idle", for this part of the test. I was aware of the "motor the dynamo" test, though didn't try this. The Club Triumph forum guys, were also surprised, at the results I was getting, though I don't think they had personal experience of this test 

A car dynamo can be used as a series or shunt DC motor and produce about 200 to 250 watts of power, The Vitesse one is 25 amp, so up to 12 x 25 watts. Watts approx amps x volts but it is an a.c. device internally, so the inductive bit loses some power.

I had tried using one to make a kids go cart long ago, but other matters intervened.

[PeteH]

On my recently departed Motorhome, the Voltage/Current from the Solar panel(s) was measured by a Dual range digital readout using a shunt resistance to measure the Current. Allowed me to measure the wattage being suplied by the panels.

Pete

[SpitfireGeorge]

Hi Guys,

Tested the dynamo as per the workshop manual and it went up to 20v, dynamo OK. Then I tested the ammeter current as per Johny's recommendation. The ammeter swung both ways, if you get my meaning, reaching just over 20A at 3000rpm so the ammeter is working. I have got another idea I will try out.

Cheers Brett

[Colin Lindsay]

From the TSSC Facebook page; I decided this forum needs the warning too, regardless of what the younger generation believes.

 

[micklewis]

best allrounder is buy a usb outlet with voltmeter .

ammeters are easy to blow thru incorrect fitment , make sure your installation is fused. many car fires have started via the ammeter 

 

mick 

[micklewis]

37 minutes ago, Colin Lindsay said:

From the TSSC Facebook page; I decided this forum needs the warning too, regardless of what the younger generation believes.

 

Some of these are only rated for 6v circuits