(Printed in the Journal of The Alliance of Automotive Service Providers, AASP) 

This January's negative degree weather brought out the typical battery, and starter problems we see year after year. A more frequent complaint that surprised me was "inoperative windshield washers". We had several complaints of this in a one week period. One of the vehicles was found to have ice in the washer bottle and another had ice in the washer nozzles. Being somewhat concerned about this issue, I decided to do some research on the freeze point of washer fluid. As typical with many things I get involved with, a "little research" turned into a full fledged investigation. One of the vehicles involved had just recieved washer fluid here from our facility. As a result, I was interested in the freeze point of the washer fluid we were using. The parts supplier we use generally alternates between two different brands of washer fluid. Both brands bottle labels state they protect against freezing to -20F.  If the labels are correct, neither brand should be icing over as our lowest temperatures here lately have only gone down to -2F. I decided to test both brands with our refractometer. Surprisingly, the refractometer showed that the two different brands had a freeze point of +10F and +18F. If the refractometer readings were true, this would explain why several vehicles were experiencing washer fluid icing. As an additional test, I left a new bottle of washer fluid outside on an extremely cold night to see if it would freeze or slush over. On the Internet, I was able to check our local airports electronic weather data center. The airports weather data center showed that the coldest temperature that night was -7F. When I got to the shop I checked the bottle of washer fluid. Much to my surprise, the washer fluid had not frozen. Now I felt more comfortable that our fluid was not the cause of the washer freeze-ups. Now, we were left with only two possibilities. Either the customer's cars still had some watered down summer mix in their washer bottles or the water/snow on the hood froze inside the washer nozzles. Just out of curiosity I decided to do some research to see if there was any published baseline rule for recommended washer fluid freeze point.

A check of the National Highway & Transportation Safety Administration's, (NHTSA), web site linked me to Federal Motor Vehicle Safety Standard, (FMVSS) #104 for new vehicle "Windshield Wiping and Washing Systems". Although there was no reference given to a mandated freeze point of washer fluid, I was very surprised at the thoroughness of the governments test procedure for wipers and washers. This test, which is required on all new cars, is designed by The Office of Vehicle Safety Compliance, (OVSC). The OVSC hires independent contractors to carry out the special test procedures. The test results are used to determine if a specific vehicle, or item of equipment, meets the minimum performance requirements for the FMVSS. The OVSC will send a new vehicle to the contractors test site. The contractor is responsible for many items including: a secure facility, securing test procedure information, calibrating test instruments, protecting test results, preventing unauthorized personnel from witnessing any test procedures, and more. In addition, the contractor must also supply the following:
1) A time keeping device that can record 0 to 60 minutes with an accuracy of + or - 2 seconds.
2) An engine tachometer ranging from 0 to 8,000 rpm.
3) Soft water with a "hardness" of 12 grains per gallon.
4) A water spray system with 2 nozzles that can spray water at 10 - 100 cubic inches per minute. 5) Non-abrasive windshield washing compound.
6) Wiper counting device that counts 0 - 1,000 cycles.
7) Oscillograph recorder at 10 ipm minimum chart speed.
8) Thermocouple sensing device ranging from 0 to 250f.
9) Anemometer that can show wind speeds of 0 to 20 mph.
10) Grease pencil.
11) Camera.
12) Test dust, fine grade, as described in SAE (Society of Automotive Engineers) code J726.
13) Measuring device for volume of test dust and water ranging from 0 - 32 fluid ozs. 
14) Hand type atomizer
15) Windshield washer fluid.

FMVSS 104 also calls for certian standard reporting definitions.
Some definitions are:
Ballooning - Unwiped areas within the wiper pattern that are round and varying in size.
Chatter - Irregular movement of wiper blade usually accompanied by temporary visible radial lines and/or noise.
Growth -The additional windshield glazing surface cleaned as the wipers cycle at high speed.
Hazing - An aerated film spread by the blade and resulting in a transient trailing band on the windshield glazing surface.
Lace Curtain - A maze of fine individual water droplets which are formed after the blade passes over the windshield glazing surface.
Scalloping - Uneven wipe at the outer periphery of pattern.
Streaking - Fine arcuate  lines of Un-wiped moisture within the wipe pattern.
Tandem Pattern - The pattern produced by the wiper blades operating in the same direction across the windshield glazing surface simultaneously.
Wiper Cycle - The wiper blade movement during system operation from one extreme of the windshield wipe pattern to the other extreme and return. 

Wiper cycle frequency is carefully tested under a controlled water spray pattern of 50-100 cubic inches per minute. Water temperature must be less than 100F. The vehicle's transmission is placed in neutral. The wipers are run at high speed for 6 minutes. During the first 3 test minutes the engine is set at idle. During the last 3 test minutes the engine is set at 2,000 rpm. The frequency of sweeps is averaged between the 2 test periods. In a second test, the wipers are set to low speed for 6 minutes. Again, the fist 3 minutes the engine is at idle and then set to 2,000 rpm for the last 3 minutes. The test results are again averaged.

Other tests include a water and dust spray combined with  75 degree air blown at the windshield at a wind speed of 1 mph. While the wipers are on high speed, a technician using a grease pencil outlines the cleaned area (including Growth) on the inside of the windshield. Upon completion, the wipers, water and air are stopped and the windshield is cleaned. A piece of clear vellum is placed on the outside of the windshield. The outline of the visible grease pencil marking is traced onto the vellum. Then this test is repeated with the vehicle's windshield washers and not the contractor's water spray system. All test results are sent in to the OVSC.

Although I did not find any base line rule for washer fluid freeze point, I did learn how complex and through the government is regarding vehicle safety and design. It is these FMVSS standards that make certain that all vehicles meet minimum safety standards in a variety of areas.