I replaced the switch and the problem is still there. the left mag, reduced rpm, the right no drop. I believe the mag is a bendix d-3000. How do you check and identify the problem? >Terry +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
I've not seen an answer to your question so I'll throw this out and anyone that sees an error in my reply can speak up. Use an ohm meter. If you don't have one and/or don't know how to use one, grab a friend that does. It shouldn't take very long to identify the problem. With the mag switch(s) off, you are looking for the "P" lead on the mag to be grounded, hence the term "grounding out the mags". Attach one lead of the ohm meter to the "P" lead and the other to aircraft ground. With the switches off, you should read "0" ohms or whatever your meter reads with the leads shorted together. With the mag switch "on", the meter should read "infinate" or full scale, or some digitals will read blank. If that check fails, leave the one lead grounded to aircraft ground and make the same check on the mag switch where that mag wire is attached. If that checks good, replace the"P" lead wire. If not, check the ground wire to the mag switch. You should read "0" ohm between that and aircraft ground. It's probly o.k. if the one mag is grounding out. Make sure you have a good ground between your engine and the point on the airframe (ground buss ? ) where everything is grounded. Most likely fault is the switch but bad "P" lead is a possibility. You might want to consider going to a different type of mag switch setup, two toggle switches, etc. to eliminate the problem in the future. If you go with a toggle, wire the aircraft ground to the "common" ( C ) terminal. Hook the "P" lead to the "normally closed" ( NC ) contact. With the switch in the "OFF" position the mag should be "grounded". When you flip the toggle to the "ON" position, the "normally closed" contact opens and the mag would be HOT. On a toggle or Micro switch that is labeled "C", "NO", and "NC", the "common" is obvious. It is connected to both sets of contacts. The "NO" and "NC" indicates the state of that set of contacts when the switch is "OFF" or "deactuated". They BOTH go to the opposite state when the switch is "ON" or "actuated". Clear as mud, right??? Larry Flesner
