TR2/3/3A Why is my coil so hot?

[mastaphixa]

I have the crane xr700 ignition system. I have measured my nondescript coil resistance at 3.5 ohms. A 30 minute drive yields a coil that is to hot to keep my hand on.

 

[Geo Hahn]

I never measured the temp of the coil after a drive - but I do know it gets hot. Of course, being bolted to the engine block is part of the reason.

 

[poolboy]

I thought the XR700 called for a ballasted ignition... How did you compensate for that with the coil you have ?

 

[TR3driver]

XR700 can be used either way. 1.5 ohm plus ballast, or 3 ohm without ballast.

 

[Sarastro]

Back when I had one of these, on my Bugeye Sprite, I noticed the same thing (with a 4-ohm coil). It surprised me, but the whole system seemed to work without problems, so I just assumed that was the way it was. As long as you are operating the way specified by the manufacturer, which you are, you SHOULD be OK. If there were a reliability problem with this system, I'm sure we all would know about it by now.

 

[mastaphixa]

Thanks for the replies, it works very well. Just for the record the coil has been moved to the drivers side fender so the engine is not contributing to the heat issue.

 

[charleyf]

I ran a Crane X-R 700 on my TR 4 for several years. I had one coil die on me while driving and after that had some issues with an occasional miss. So I changed back to a regular points distributor.
My advice is to carry a replacement coil. But I hope you have no issues.
Charley