Obviously if there is a problem with the truck I would rather fix it than retrofit a heater and a thermostat. The truck is a Linde B30TES with equipped with BTC2000 transistorized controls. We have 2 identical trucks and have taken the travel card out of each machine, put it in a freezer overnight, reinstalled it and neither truck will pick up the forward or reverse contactors. We have also disconnected the thermal switches at the drive motors and the contactors still won't pick up. The cards have been spayed with a sealer that also acts as an insulator that Linde recommends in cold storage applications.
The other odd thing is that when then truck quits you can push or tow it and the contactors will pick up and the truck will operate fine. I have been told the reason for this is that the drive motor(s) have become generator(s) and have sent a spike to the card.
I can see where there might be a problem if only one truck had a problem but it seems to be way too coincidental to have both trucks malfunction identically. If you have any suggestions, I'm all ears.