One problem related to turn signal flasher unit has been reported for the 1998 Ford E-350. The most recently reported issues are listed below.
Vehicle sold and factory equipped with trailering package which includes factory trailer wiring. Turn signals & hazard flashers do not flash in accordance w/ 49cfr, 571. 108 when trailer attached to factory wiring. Dealer has found electronic flasher from Ford is not sufficient to operate with trailer. Flasher is rated as "2/4 flasher" (2 turn/4 hazard lamps). Ford does not offer heavy duty flasher sufficient to operate vehicle & trailer turn / flasher lamps. No aftermarket manufacturer has been found that makes a flasher unit that will operate in this vehicle. Standard "heavy duty" flashers blow all turn / flasher / brake light fuses. Creates extreme danger as turn signals and hazard flashers fail or are insufficient to operate in traffic with trailer attached. Only remedy is to convert trailer lamps to led lamps. Cost $150. 00 - $250. 00 per trailer.