Mag check

Relatively new owner of a bought -7A. Recently, the left mag shows zero RPM drop during mag check. Could this be an issue? Appreciate any feedback!

Zero RPM drop could be an indication that the P-lead is broken or the switch is not working properly.
A quick check is to see if the engine will turn off at idle by using the switch. That will verify that the P-lead is good if it turns off. If it stays running then check the P-Lead.
If it does turn off, then I would suspect the switch.

Vic

Be careful. That Mag could be HOT !

I'm no expert but you reminded me of my own experience. MY mags were barely dropping during run-up. I had bought the plane as well and after getting some "issues" worked out, it turns out she really needed some attention. At any rate, my mechanic rebuilt the mags and they were way off on timing (among other issues I think). They have been very consistent at around 50 rpm drop now after almost 400 hours.

It seems like you are in need of a rebuild (re-timing at a minimum) or you are running on one mag. Either one should get some quick attention I would think.

Lean the engine so that you can just get it to 1700rpm, then try the mag check. This will cause a much more significant drop in rpm on the mag check (if the mag is working).

If you still get no drop then, as others have said, you likely have a broken p lead and should be very careful as you have a hot mag.

Thanks so much for your responses. Thought I might have been asking a dumb question, but looks like I might have a serious safety problem.

If you have an electronic ignition on the left 0 drop is normal.

If last time you flew and things where fine, and then all of a sudden they are not, my guess is a broken P-lead, usually the terminal. Do Vic's test. Of course this is all assuming standard mags.
If you do find it is a broken terminal, here is a thread that may help avoid this in the future.
http://www.vansairforce.com/community/showthread.php?t=147243&highlight=Failed+terminal