This content is not included in
your SAE MOBILUS subscription, or you are not logged in.
Windshield Defrosting Systems Test Procedure and Performance Requirements—Trucks, Buses, and Multipurpose Vehicles
- Ground Vehicle Standard
- J381_200901
- Revised
Downloadable datasets available
Annotation ability available
Sector:
Issuing Committee:
Language:
English
Scope
This SAE Recommended Practice establishes uniform test procedures and performance requirements for the defrosting system of enclosed cab trucks, buses, and multipurpose vehicles. It is limited to a test that can be conducted on uniform test equipment in commercially available laboratory facilities. Current engineering practice prescribes that for laboratory evaluation of defroster systems, an ice coating of known thickness be applied to the windshield and left- and right-hand side windows to provide more uniform and repeatable test results, even though under actual conditions such a coating would necessarily be scraped off before driving. The test condition, therefore, represents a more severe condition than the 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 or warmed up before driving) and since defrosting under steady-state over-the-road operations is the main concern, test conditions 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 on the 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 the performance of one defroster design to another defroster design, then the external coolant source approach (Test A) will yield the most comparable results. If the test is being conducted to validate the defroster installation on a specific vehicle model 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.
Rationale
The current SAE J381 test procedure provides two separate means of heating the coolant during testing, but these two approaches can provide very different results. If the engine is used to heat the coolant, the engine rpm and engine load criteria are neither clear nor consistent.
There are two distinct reasons to test a defrost system:
-
a
To compare two or more alternative defroster systems during the design process.
-
b
To compare the defroster performance of a specific vehicle and engine configuration to an established standard.
This revision recognizes these differences in the reasons for testing, and provides specific test conditions depending on the test intent. Variations of the test between gasoline and diesel engines are eliminated with the rationale that how well the window clears should not be a function of the engine fuel source.
Diesel and gasoline engines in the past ran at very different rpms, but today most truck gasoline engines run high idle rpms at similar speeds when compared to their diesel counterparts.
The chamber wind condition was increased to up to 5 mph because this is easier for all chambers to meet and this should not significantly affect the results
Updated the test report template to match the procedure
References to the type of cameras that could be used were removed because such specific recommendations do not keep pace with advancements in technology.
Recommended Content
Topic
Data Sets - Support Documents
Title | Description | Download |
---|---|---|
Unnamed Dataset 1 | ||
Unnamed Dataset 2 | ||
Unnamed Dataset 3 | ||
Unnamed Dataset 4 | ||
TABLE 1 | MINIMUM PERCENT OF WINDSHIELD TO BE DEFROSTED | |
TABLE 2 | WIPED AREA VIEWING REQUIREMENT |
Issuing Committee
Truck and Bus Windshield Wipers and Climate Control Comm
The responsibility of Windshield Wipers and Climate Control Committee of the Truck and Bus Body, Occupant and Environment Steering Committee is to initiate, develop, review and approve the recommended practices, standards, and information reports related to windshield washer/wiper systems, defroster/defogging systems and components that affect the interior climate and environment of occupied areas of trucks, buses and multi purpose vehicles intended for on-highway use.
Reference
Number | Title |
---|---|
J941 | This document is not part of the subscrption. |
* Redlines comparisons are available for those standards
listed in the Revision History that contain a radio button. A
redline comparison of the current version against a revision is
accomplished by selecting the radio button next to the standard and
then selecting 'compare'. At this time, Redline versions only exist
for some AMS standards. SAE will continue to add redline versioning
with ongoing updates to SAE MOBILUS.