Product Code:SAE J381
Title:Windshield Defrosting Systems Test Procedure and Performance Requirements--Trucks, Buses, and Multipurpose Vehicles
Issuing Committee:Truck And Bus Windshield Wipers And Climate Control Comm
Scope:This SAE Recommended Practice establishes uniform test procedures and performance requirements for the defrostingsystem of enclosed cab trucks, buses, and multipurpose vehicles. It is limited to a test that can be conducted on uniformtest equipment in commercially available laboratory facilities. Current engineering practice prescribes that for laboratoryevaluation of defroster systems, an ice coating of known thickness be applied to the windshield and left- and right-handside windows to provide more uniform and repeatable test results, even though under actual conditions such a coatingwould necessarily be scraped off before driving. The test condition, therefore, represents a more severe condition thanthe actual condition, where the defroster system must merely be capable of maintaining a cleared viewing area.Because of the special nature of the operation of most of these vehicles (where vehicles are generally kept in a garage orwarmed up before driving) and since defrosting under steady-state over-the-road operations is the main concern, testconditions have been adopted which assume that the engine is warm before the vehicle is driven.There are two options for producing hot coolant in this recommended practice. Testing using these two approaches onthe same vehicle will not necessarily provide identical results. Many vehicle models are offered with optional engines,and each engine has varying coolant temperatures and flow rates. If the test is being conducted to compare theperformance of one defroster design to another defroster design, then the external coolant source approach (Test A) willyield the most comparable results. If the test is being conducted to validate the defroster installation on a specific vehiclemodel with a specific engine, then using the engine to heat the coolant (Test B) will be more appropriate.This document will be reviewed and revised as technological progress in vehicle defroster test procedure requires.