M20K low boost fuel pump resistor

[rainman]

I recently had a somewhat scary event while flying in San Antonio airspace. I smell something burning and then smoke start to come from under the instrument panel. I declared an emergency and safely landed at Stinson Field. The mechanic there told me the resistor that goes to the low boost fuel pump motor had burned out. He said he didn't know why the resistor is in place and is unsure how to proceed.  Is this a normal electrical wiring to the low boost motor in a 231? Is it safe to fly it to a MSC the way it is? I'm a low time pilot and this really got my attention!

[231flyer]

There should be an in-line fuse (10A) on the same circuit.  Since the resistor blew and not the fuse you probably had a higher rated fuse. Please check if you can still prime or run the high-boost setting ( I am assuming they are both in-op). You need to install the correct fuse, replace the resistor, and then find the source of the short.  Mine turned out to be a chafffed wire from the primer switch (Btw the low boost and primer activate the same circuit).  You need this circuit in working order for a safe flight.  Besides priming the engine the low-boost is your primary safety standby pump.  The high boost switch by-passes the resistor thus running the standby pump at the "higher" flow rate. 

[rainman]

Thanks, I'll forward this information to the mechanic.

Ray