I have a 1445, but I think that the wiring is similar.
It could be a bad starter, but I would double check the wiring to the external solenoid and the starter.
PT has added a second solenoid to the starter circuit on the Deutz. My understanding is that the internal solenoid requires full voltage to close. So there is a starter integral to the Bosch starter, and an external solenoid. If the external solenoid doesn't close, then the internal solenoid doesn't get power, but you need both to function. I would check voltages at the two solenoids first. When my starter died, even bypassing both solenoids didn't get the engine to turn over.
I have had to replace the solenoid once (cracked support bracket), and the starter once. I have also repaired the wire to the PT solenoid more than a few times as it vibrates and cracks the crimped connector. Currently, the wire has a crimped/solder/heatshrink attachment, with a cable tie to one of the heavy gauge cables to the starter to reduce vibration at the solenoid attachment.
If I had to guess, I would bet on the wire having pulled out of the crimp, or the crimped connector being broken. My other guess would be a bad starter. I got a replacement at my local O'Reilly's/Autozone. The external solenoid was also available there.
All the best,
Peter
My 1845 has intermittently failed to turn over when hot for several years. On all previous occasions I used a charger to assist and the engine started. Sometimes I found connection problems that explained why I was having the problem but recently I have not found any connection problems. A couple of weeks ago it happened but after the engine cooled it started normally. Today, even with the charger the engine would not turn over. The solenoid engages and the volt meter drops to near zero--even with a large charger attached--but the starter doesn't turn the engine. I am writing this before the engine has cooled so I don't yet know if it will start once cool. I am suspecting it is a bad starter but would appreciate any suggestions.