4. When the verb in the main clause is in one of the past tenses or in the conditional, the imperfect subjunctive is used in the dependent clause:
Preterite
Quise que (él) me escribiera.
I wanted him to write me.Imperfect
Quería que mi hijo me escribiera cada día.
I wanted my son to write me every day.Past Perfect
Había querido que mi hijo me escribiera en su ausencia.
I had wanted that my son to write me in his absence.Conditional
Querría que mi hijo me escribiera durante su viaje.
I would like my son to write me during his trip.