Curtis Instruments does not always make legacy manuals easy to find on their main homepage. However, several reliable sources exist.
To extend the life of your controller, follow these maintenance steps outlined in the original Curtis documentation:
If you don’t follow this exact sequence from the manual, the controller will ignore your inputs. curtis 3501 manual
Because this controller operates with complex logic, attempting to repair or adjust it "blind" can lead to catastrophic failure. This is why the is not just a nice-to-have—it is a mandatory safety tool.
Disclaimer: This article is for informational purposes. Always refer to the original equipment manufacturer’s safety guidelines. Electrical vehicle repair should only be performed by qualified technicians. Curtis Instruments does not always make legacy manuals
Here’s a forum-style post you could use or adapt:
Main things I need:
Navigate to the "Support" or "Documentation" section. Use the legacy product search. For the 3501 series, look under the (Permanent Magnet Control) category. Direct links often change, but a persistent search for "Curtis 3501 troubleshooting guide" will yield results.