I missed that this was a car wash. Ahh, memories... Not all good. I had 3 clients over the years who built car washes and in fact I once considered building one as a side business, they can be surprisingly profitable if you find the right location.
A common way this is done, depending on local weather conditions, is for the drying blowers to have heaters inside. That's because if someone goes through on a day when humidity is really high, it doesnt dry the car. Or if the air temperature is already low, the high speed of the blower air can bring it down to below freezing on the metal surfaces of the car and cause ice, which leaves water spots after it melts. Either condition ends up bringing the customer back for a freebie. So the heater coils are added to the blowers. But it takes too long for the elements to heat up if turned off so when there are multiple cars, they are left on in between. That then means that the blowers must ALSO be left on, otherwise with zero air flow across the heaters, they burn out. So in between cars they will have a VFD that drops the blower speed down to a minimum flow level deemed necessary to protect the heater elements. If there is no VFD, the blowers might be two speed, same reason. If that's the case, you would have 2 or 3 contactors per motor, depending on the type of 2 speed motor used.
Cheap versions of this just use ATL for the blowers, but attempt to use delayed Off commands combined with the spin-down time of the blowers as a buffer to maintain some air flow across the heaters. That never works out in my experience and the symptom of that not working is that the motors over heat because they are constantly being cycled on and off. That may very well be what you have going on here, because you have the symptom and you mentioned timers. The timers would be part of a two speed starter as well, but it's not likely that you would have these symptoms if that were the case. If that's what is going on, nuisance tripping of overloads and the eventual loss of the motors is just going to have to be considered a cost of doing business on the cheap (false economy really), unless the owner is willing to pony up for a more expensive initial outlay for an upgrade. There are aftermarket car wash control system builders who specialize in exactly that by the way.
You cannot do this with a soft starter by the way. I tried, same result as above. Soft starters, contrary to what some salesmen will tell you, do NOT reduce motor heating from high duty cycle. The watts wasted as heat in starting the motor are lowered because the current is reduced, but the amount of time it takes place is extended at the same time, so the net ENERGY given up as heat in the motor stays the same (debated by some that it might actually be more, but it's my opinion that it nets out as equal).
