I recently purchased a Mayco line pump to add to our business. It was used and I knew it had some issues when I bought it. I need some help. 

When you try to pump in automatic at high idle it lugs engine and won’t switch cylinders. When you jog manually you can jog til cylinder hits the end of stroke and it lugs down. Swing tube switches freely and fast but cylinders won’t change directions except with jog switch. 

I passed a wrench under proximity switches. One side lights up brightly and other side is a bit dim. It seems to me that if one side was bad it would at least switch half the time. 

Any ideas?

Sent you a PM

the bad prox switch will affect the opposite barrel.

had one of my check valves suck in a little slurry into the fitting. inspect the one closest to the wash box, cheep so just replace it.  

Just an update on this for future readers. The previous owner had decided to tidy up some wires and had gotten the prox switch signal wires to the wrong switch. They were swapped. Swapped them back and away it went!