Coil Testing

This topic has 7 replies, 3 voices, and was last updated 4 years, 6 months ago by sidevalve44.

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August 31, 2021 at 5:45 pm #37799

sidevalve44
Participant

Although I do not know much about coil testing I thought I would use my Handheld Multimeter to see what readings I got.

I attached one probe to the HT lead and one to the lead that comes from the coil to the points (points removed) and condensor. Setting Multimeter to 20K on Resistance I got a reading of 6.93.
I then repeated the exercise but this time attached the probe to the earth wire that comes from the coil (other one still attached to HT lead) and got the same reading, 6.93.

What is this telling me (if anything) ?

August 31, 2021 at 8:27 pm #37801

wristpin
Participant

The HT lead is connected to the secondary coil winding. Check resistance between end of HT and earth. The primary winding is earthed at one end and the other probably shares a common terminal with the condenser on the points. Disconnect the condenser make sure that the points are open and take a resistance reading between that lead and earth.

September 1, 2021 at 8:33 pm #37809

sidevalve44
Participant

Hi Wristpin.

Thanks for the advice.

I checked the resistance between the HT lead and earth and the reading was 0

I then checked the resistance between the lead from the coil to the condenser (condenser removed) and the reading was 2.2 with the multimeter set on 200.

I also got the same reading if I applied the probes to the coil earth wire and the lead from the coil to the condenser.

Points were refitted but in an open position.

What is this telling me ?

September 2, 2021 at 6:41 am #37810
charlie
Keymaster
The following diagram of the Villiers flywheel magneto can be found at https://www.historywebsite.co.uk/Museum/Engineering/Villiers/Villiers9.htm
This should help explain the circuit.
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September 2, 2021 at 11:21 am #37814

wristpin
Participant

Your resistance reading on the primary is probably ok but the zero on the secondary is not good – a good coil will show resistance on both windings.
A bad winding on my meter will either show 0.L ( open loop ) or 0.00 for a dead short – no resistance. So the zero on your secondary suggests an internal dead short – not unusual for an old coil with internal corrosion.

September 2, 2021 at 5:36 pm #37817

sidevalve44
Participant

I’ve located and bought a new (pattern) coil for £11.26 plus condenser and points for £8.99, all on-line.

Gaskets will have to be re-used with Wellseal or made.

Looks like I’ll soon have it running !

September 3, 2021 at 8:06 am #37818

charlie
Keymaster

£11.26 sounds cheap for a coil, I usually pay around £50-£70 for a Villiers type coil using reputable suppliers on line.

September 19, 2021 at 4:50 pm #37889

sidevalve44
Participant

£11.26 for a coil is cheap I know, but it fits and it works, so I’m not complaining.

Villiers coils are expensive.

Tecumseh ones were about £30.00+
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