Electrical help please

Gents, I have an Alco gen set powered by a JAP2s which produces 24V and runs a lighting box. I tested it today and I am getting readings of a shade under 200VDC but the multimeter is fluctuating wildly between about 170 and 200.
The last time out I lost power to the box which turned out to be a loose wire in the socket. I put it back but managed to get it into the earth 'hole' which is connected to the case/engine. I cannot remember if it was the positive or negative.  
I am wondering it I may have blown something but I cannot think what, any suggestiuons what may be the problem please
TIA

Gents, I have been told it could be a regulator of some description that has failed.

Hi Mick what sort of Multi meter are you using DVM or Analogue ? if DVM is it an auto range model ? if its a DVM auto range model you can get funny readings and connect a 24V 21W lorry indicator bulb to give the generator some load and see what happens kind regards Bob

Hello Bob
I have a Mastertech M92A Digital Multimeter, when I have tested it on the gen set previously it worked fine and gave a reading of 24v. I have also checked it on batteries and it works OK on 1.5v (AA) and 12v so it has to be at the gen set where the problem is.