I'm running a set-up of a Losi SCTE, RX8/Pro4 4600kV, a Spektrum DX3R with S6040 servo and a Fantom 5200 50C 7.4v LiPo.

I was racing last weekend and my servo would just quit for no apparent reason. One guy at the track let me borrow a homemade "glitch buster" and that seemed to help, but it still did the same thing one time near the end of a run even with the GB. That made me think the GB wasn't doing anything.

Today, it did the same thing in warm-ups. I believe the issue starts when the ESC fan kicks on. I unplugged the fan and did not have an issue the rest of the day. I really don't like running without the fan, but I really don't want to lose control of a SCTE at 40 mph either.

Thoughts or tips for me? I really don't want to have to run a BEC. Is it possible that the ESC fan is drawing enough current to make my servo/radio wig out?

you could find yourself a 7.4v compatible fan of the same size and wire it directly to the battery. that should take care of it.

It sounds like you are drawing too much current for the BEC. The Spektrum servos pull some decent power and if you are getting brown outs, especially if it is coming out of corners into acceleration zones, that is usually when it happens. I would run a cap no matter what, and wiring the fan directly to the battery might help. The other option is that which you did not want to do, which is run an external BEC.

It is a fairly common issue, especially with Spektrum radio equipment and high amp draw servos (Spektrum and Savox, and anything listed as HV).

Running a seperate bec is the only way to go IMO. I run one on every car I have. A really good one is a tunigy hi voltage sold on hobbyking for like 8 or 9 bucks.

The castle 10a bec is also a great option. Requires castle link to change from the default (5.1 i think) volts. It might be a better option than buying a 7.4v fan since you could end up spending about the same ammount. If you have a bec you can set to 7.4v and run HV servos.

What RX are u using? If its not a DSM2 I.e(SR3100 & SR3250) then I bet it's ur problem they hold there voltage much better.