try checking the potentiometer circuit.

the 1a circuit just bypasses the controller and provides full battery voltage to the motor as soon as the directional contactor closes.
I would still like to see a picture of the controller to be sure, but almost any part you need for the controller can either be had at fight systems (FSIP.biz) or if they don't have the part on the shelf to send you first, you can send them the part and their re-builders can go through it and return you a completely repaired unit.

Thank you for replying so quickly! All the contacts are working, forward and reverse both make contact. I have narrowed it down to the a1 switch. If you manually depress it, the truck will move forward and back. We pulled the board off and it had some pretty severe corrosion spots. If this is the problem (you think?), then where would I find an economical replacement or solution?

Hello Lora, thank you for including the serial number for this forklift, as there are a few differnt models of controllers used in M40 cats, and having a serial number will make it easier to know which controller YOUR truck uses, however I do not have any referaces for a unit that old. Don't give up hope just yet though.
I would normally suggest that someone with a problem start a new thread and use the model and a very brief description in the subject of the thread (like no drive), but since we are here, let's just "go with it".
First I would want to know if the forklift still lifts, and if there is ANY sign of it trying to drive (no clicking or any other sound or motion) when you sit on the seat, turn on the key and put it in gear?
It would be my bet that the washing and trying to drive it before it had enough chance to air dry has indeed done some damage. [I hope you don't wash your TV, stereo or computer too. ;-) ]
There are a number of fuses in this unit, and it may be just a blown fuse (hopefully) but be sure to get the drive wheels off the ground and disconnect the battery before attempting any tests or repair on this unit. some minor corrosion on the contacts is pretty much normal, as they carry a LOT of electricity, and do not try to clean the corrosion off with any sort of file, just as long as they work at all.

OK, it's a Towmotor model M40 (on the sales receipt) model 140 on the I.D. plate serial number 23V769. 4,000 lb capacity, electric General Electric motor. there is some corrosion on the contacts and it got washed right before this started. Possibly moisture? It's been 5-6 days.

You seem to be in alot of these discussions so I am going to ask you my question... my Cat elec. forklift won't go forward or back although all the switches are testing good. I printed off a discussion from 2006 where you helped someone with the same problem on their Crown. Where is the controller box on this very old Cat? I am going to my shop in awhile so I will be able to get the model and serial for you.