Automotive Refractometer for Coolant, Battery Acid, Windshield Washer Fluid, and AdBlue®

Frequently Asked Questions About Automotive Refractometers

Refractometers allow for the quick testing of various liquid operating fluids based on their refractive index. Depending on the device and the scale available, they can be used, for example, to assess the antifreeze content in coolant, windshield washer fluid, battery acid density, or the concentration of AdBlue®. Here, we answer frequently asked questions about the use of refractometers in automotive repair shops.

• What can be measured with an automotive refractometer?

  That depends on the scales of the specific refractometer.

  The Leitenberger FT 2030.1, for example, has scales for testing:

  • antifreeze in coolant,
  • antifreeze in windshield washer fluid,
  • battery acid density,
  • urea or AdBlue®.

  Other refractometers may be designed for specific coolants or individual media. Therefore, you should always use the scale intended for the specific medium.

• How does a refractometer work?

  A refractometer measures the refractive index of a liquid. This index varies depending on the composition or concentration of the liquid.
  
  To take a measurement, a few drops of the sample are placed on the clean prism surface and spread evenly. The measurement result is then read from the corresponding scale or the light-dark boundary.
  
  The exact procedure, calibration, and temperature compensation depend on the specific device.

• How do you check the antifreeze concentration of the coolant using a refractometer?

  First, take a small sample of the coolant and place it on the clean surface of the prism.
  
  The corresponding antifreeze level can then be read on the scale designated for the specific coolant or glycol being used.
  
  It is important that the refractometer is suitable for the coolant in question. Modern vehicles use a variety of coolant technologies and blends. Therefore, in addition to the measured value, the specifications provided by the vehicle and coolant manufacturers are always relevant for evaluation.

• Can a refractometer determine whether a coolant is still in good condition overall?

  Only to a limited extent. Depending on the model, a refractometer can, for example, assess concentration or antifreeze protection. However, it does not automatically provide a complete picture of the coolant’s chemical condition.

  Aging, corrosion protection, contaminants, pH, or electrical conductivity may require additional testing.

  In modern high-voltage and fuel cell systems in particular, other coolant properties can be critical. For such applications, conductivity meters and coolant analyses are available, for example.

• Can AdBlue® be tested using a refractometer?

  Yes, provided the refractometer has an AdBlue® or urea scale.

  AdBlue® is a standardized urea solution AUS 32. The specified composition is 32.5 percent urea and 67.5 percent demineralized water. The quality requirements are defined in the ISO 22241 series of standards.

  A suitable refractometer can be used to verify whether the concentration is within the specified range. This allows, for example, significant dilutions or incorrect mixing ratios to be detected.

• Can battery acid be tested with a refractometer?

  Suitable refractometers have a scale for determining battery acid density.
  
  In suitable lead-acid batteries, the acid density provides information about the condition or state of charge of the electrolyte.
  
  However, such a measurement is only possible if the electrolyte is safely accessible, depending on the battery design. In sealed or maintenance-free battery systems, there is often no provision for draining the electrolyte.

• Can windshield washer fluid also be tested with a refractometer?

  Yes. You can check the antifreeze protection of windshield washer fluid using the appropriate scale.
  
  This is especially important before the cold season begins. Be sure to use the scale designated for windshield washer fluid, as its composition is not the same as that of engine coolant.

• Can a standard automotive refractometer also be used to test coolant in electric and fuel-cell vehicles?

  Not across the board.

  Some electrical systems—and fuel cell systems in particular—use special coolants with very low electrical conductivity. In addition to freeze protection and concentration, the coolant’s electrical insulation properties play an important role in these systems.

  For such applications, an additional conductivity measurement may be required.

  Leitenberger Autotestgeräte also offers the RFM 05_RGM, a refractometer specifically designed for testing the antifreeze properties of ready-to-use coolant mixtures for PEM fuel cell systems.

  It is essential to comply with the vehicle or system manufacturer’s approval requirements when using these coolants.

• Why does the prism of a refractometer need to be clean?

  Even small amounts of residue from a previously measured medium can contaminate the next sample and alter the measurement result.
  
  Therefore, the prism surface should be cleaned after each measurement in accordance with the operating instructions, and all residue from the previous medium should be completely removed before the next measurement.
  
  This is particularly important when the same refractometer is used for different fluids such as coolant, windshield washer fluid, and AdBlue®.

• What kinds of errors can occur during a refractometer measurement?

  Possible causes of implausible measurement results include:

  • incorrect scale for the medium being tested,
  • a dirty prism surface,
  • a contaminated sample,
  • air bubbles between the sample and the cover,
  • an incorrectly calibrated instrument,
  • an inappropriate sample temperature,
  • use with a medium for which the refractometer is not intended.

  If unexpected results occur, you should therefore first check whether the device is suitable for the medium in question and whether the measurement was performed in accordance with the operating instructions.