India 'A' were 56 for 1 in 7.4 overs with Dhawan (34) and Prashant Chopra (6) at the crease when the skies opened up. The India opener struck six boundaries during his 21-ball unbeaten knock.
After a stuttering start, Dhawan found his touch and hit some superb shots through the off-side. Earlier, sent in to bat by the home team captain Shreyas Iyer, South Africa 'A' made 137 for one in 25 overs in a rain-affected game.
After play started late, heavy showers forced the players indoors with the visitors at 108 for one in 22 overs.
The game was then reduced to a 25 overs-a-side affair and SA 'A' added 29 more runs. The revised target for India A was 193 in 25 overs.
Heinrich Klaasen's (21) late assault and Reeza Hendricks (60) helped the visiting team to finish with a flourish.
The big-hitting Klaasen hit Ishan Porel for two consecutive sixes in the penultimate over and looked good for more.
However, Tushar Deshpande bowled a dream final over, with five consecutive dot balls to Klaasen.
Matthew Breetzke (25) and Hendricks provided a bright start, hitting some lovely shots. Breetzke hit a superb six over covers off Deshpande, which stood out.
India 'A' lead the five-match ODI series 3-0.
Brief scores: South Africa 'A' 137 for 1 in 25 overs (Reeza Hendricks 60, Matthew Breetzke 25, Heinrich Klaasen 21 not out, Rahul Chahar 1/18) vs India 'A' 56 for 1 in 7.4 overs (S Dhawan 34 batting).