Ignition coil

Farmer42

Club Member
Spoke too soon!!:(

Went for a drive yesterday and after about 20 mins i started getting a misfire and the revs bogged down. I pulled over and checked all the connections and plugs etc but decided that it must be the coil again. First, I by-passed the ballast resistor but still had problems and the coil got quite hot which was not the case when the resistor was connected.

Luckily I still had the OEM 280ZX coil in the boot that I had borrowed off Huw so I pulled over again and swapped them over. Instant success as it ran sweet and did so for a good hour's drive after that. It seems that my dizzy has a particular taste for the original STC-30 coil and nothing else will do. I still have the ballast resistor connected up which has prevented the coil from getting hot and tried it again today where it started fine and ran for 10 mins without a hiccup.

It seems that I need to stick with the STC-30 coil but keep it ballasted.
 

toopy

Club Member
I thought coils getting hot was normal, too hot to touch for more than a second or two probably not good though!
 

Huw

Club Member
Ohhh sorry to hear that Paul. Thought you had nailed it mate. You can keep hold of the my spare, spare if you want.

Huw
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
On a car with the ballast resistor 'bypassed' (280ZX Dizzy install) has anyone ever considered the length of the circuit from the ignition switch to the coil.

If you remove the ballast resistor and connect the wires together (as most do when fitting an electronic 280 dizzy and coil) the circuit runs from the ignition switch through the tacho to the ballast position, through the 'short' and back to a connection near the ignition switch and then back to the coil +ve terminal.

I shorted mine near the switch to save two lengths (one G/W and one B/W) of the car.

And why is the ballast resistor under the coil? It doesn't connect directly to the coil - it could be on the bulkhead and save wiring.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
Also it's quite common to see 'add-on' connections to the +ve terminal of the coil e.g. electric fan. That's not good practice surely because that circuit is not fused and is only a small gauge wire. Even if the 'add-on' has an inline fuse it's going to draw the 'blow' current through the wiring and tacho.

A coil 'pulls' about 4A.
 

toopy

Club Member
Also it's quite common to see 'add-on' connections to the +ve terminal of the coil e.g. electric fan. That's not good practice surely because that circuit is not fused and is only a small gauge wire. Even if the 'add-on' has an inline fuse it's going to draw the 'blow' current through the wiring and tacho.

A coil 'pulls' about 4A.

I think most of the time that connection would only be used to power an electronic thermostat and/or the fan relay, the main feed current coming from another source.
 

Rob Gaskin

Treasurer
Staff member
Site Administrator
I think most of the time that connection would only be used to power an electronic thermostat and/or the fan relay, the main feed current coming from another source.

Maybe. I'm also trying to understand how the tacho works if there is a constant current to an electrical device instead of the pulsing caused by the distributor?
 

jonbills

Membership Secretary
Site Administrator
I think the tacho has its own power supply, and the wiring from the distributor just provides a signal pulse.
 

jonbills

Membership Secretary
Site Administrator
oh, I misunderstood.
well it didn't hurt my tacho with a relay for fans attached.
 
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