Hope the below is of help
1. Dave had a controller (3 digit, three button controller) with a Shurflo 6.4l/min pump. Pump was 3.5 yrs old.
2. Current draw was 8A. Battery flat by lunch time. Pump replaced.
3. New pump uses 3A. Flow turned up to 80, cal set to 80. Bypass controller ok. New battery but no change.
4. Bought new pump (shurflo 5.2lt) and new controller. Works ok. (But old controller does not).
At first it sounded like there may be a restriction in Dave's system, not a full blockage but maybe a restriction like dirt lodged in a joint or a mismatched fitting. Air in system can also restrict flow and increase high current draw (but air can be forced out over time and given how long Dave's problem continued this seems unlikely).
Another common misconception is that people need a very powerful pump with a high flowrate. But a 5l/min is usually more that adequate, because the flow is restricted by the DI vessels, the bore and length of the hose and the jets on the brush. It is more important to have sufficient pressure to overcome these restrictions, 60PSI is usually adequate but most people use a 100PSI 5l/min pump which is perfect.
If Dave re-fits his old controller and the problem comes back then the conclusion in that the controller does have a problem. Please send it back to us and we will try to diagnose the problem