IP67 and EMC in High-Voltage Heaters: What to Check Before Installation

Customers typically do not contact us because the heater itself fails to meet the specifications listed in the datasheet. They often call in February—when vehicles frequently display error messages on cold mornings—even though the heater passed all inspections upon arrival at the warehouse; the relevant technical documentation clearly states that it “complies with the IP67 standard” and “has passed EMC (electromagnetic compatibility) testing”—and from a technical standpoint, these descriptions are indeed accurate.

What we’re discussing today is precisely the gap between “laboratory test environments” and “actual winter operating conditions.” Our A, E, H, and Q series heaters all feature an IP67 protection rating, but it’s important for us to explain the limits of this rating.

What exactly does the IP67 test cover?

The IP67 standard is derived from the IEC 60529 specification. In this standard, “6” indicates complete protection against dust, while “7” indicates immersion testing—though this test is actually quite mild: it involves submersion in still, clean water at a depth of one meter for 30 minutes. The test does not involve high-pressure water jets or water mist. Furthermore, the test subjects are brand-new products, and the connectors are mated strictly in accordance with the specifications.

Passing this test does indeed have value. Under a vehicle’s chassis, heaters are exposed daily to road splash, a mixture of mud and snow, and standing water. It is important to note that you should not overinterpret the test implications represented by these two numbers.

Limitations of Protection Ratings: High-Pressure Washing, Accidental Conditions, and Unconnected Interfaces

Compared to deep-water immersion, high-pressure washing is more likely to cause damage to heaters. A high-pressure washing zone is by no means a simple immersion environment: within a half-meter distance, high-pressure water jets directly impact the sealing interfaces—this falls under the IP69K protection category, which is entirely different from IP67. Before determining the installation location, be sure to understand the car-washing methods used at repair shops or car wash stations, as well as the distance between the washing equipment and the heater.

“Aging” is another key factor: the seals on which the IP67 rating is based have not been tested for thermal cycling (repeated temperature fluctuations). If a connector is subjected to the harsh conditions of five winters—including cold starts at -40 degrees Celsius, exposure to high-temperature coolant, chassis vibrations, and even violent tugging on the wiring harness—its sealing condition will no longer resemble that observed during initial laboratory testing. Whether the product remains intact after five years depends on the formulation of the sealing material and the structural design of the connector—information that cannot be found in the technical specifications.

Test conditions are critical. The IP67 standard assumes that the connector must be in the “mated” state. A spare heater does not provide this level of protection when it is not connected; similarly, during vehicle assembly, if the heater is installed but the connector is open, the required protection rating cannot be achieved. We have received feedback such as this: water entered the interior of a heater that had never even been connected—yet the customer blamed the seal, unaware that the seal had not even had a chance to function. The protection rating (IP rating) applies only to the external environment and assesses the enclosure’s ability to resist external dust and water. Coolant, however, is present inside the enclosure—whether due to porosity in castings, hose connections, or coolant freezing while the vehicle is parked—and these potential hazards can cause failures at any time.

The impact of electromagnetic compatibility (EMC) is bidirectional, and laboratory test environments differ significantly from actual vehicle environments.

High-voltage PTC heaters are switching loads with power ratings of several kilowatts. EMC testing is conducted on laboratory test benches—for example, in accordance with the ISO 11452 standard (Class 3)—under specific wiring harness, ground plane, and load conditions. This testing environment is highly controlled and repeatable, yet it differs entirely from the actual vehicle environment.

In actual vehicles, wiring harnesses are longer and are not routed along an ideal ground plane but rather run close to the chassis; the selection of low-voltage ground points depends on the body assembly process. These factors can alter test results, which explains why the in-field failure behavior is so characteristic: CAN bus errors occur only on cold mornings when the heater is operating at full power, yet the fault often disappears by the time the vehicle is brought to the repair shop. The heater itself did indeed pass laboratory bench testing, but the actual installation environment introduced failure factors not considered during bench testing.

Interference signals may also enter in the opposite direction: load dump, startup transients, and interference generated by other devices on the same power supply circuit can all enter the heater’s electronic system. In addition to EMC considerations, attention should also be paid to protection mechanisms—which serve as the last line of defense against equipment damage caused by transient interference—including overvoltage, undervoltage, overcurrent, short-circuit, and overheat protection, as well as high-voltage interlock (HVIL) functionality.

A Key Metric to Compare

If asked which parameter in the data sheet best reflects a product’s actual service life, we would point to “insulation resistance.” Our products specify that insulation resistance in the high-voltage section must reach 100 MΩ or higher (measured at 1,000 V DC). Over many years of operation, the insulating properties of coolant gradually deteriorate, and seals may also develop minor leaks; this specification is specifically designed to provide a margin of safety against these gradual (rather than sudden) changes.

When comparing this specification, it’s worth asking a critical follow-up question: Is this a design target on paper, or an actual measured value from mass-produced products? In sales emails, the two statements may sound the same, but after the product has been in service in a fleet for four years, they become vastly different.

Five Questions and Their Implications

You can ask these questions of any supplier (including us). These questions can be answered without laboratory testing and will help you determine whether the rating is based on actual test results for your specific configuration or was simply “borrowed” from a generic data sheet for the product series.

1. Is this test report specific to the current configuration (including connectors), or is it a generic report applicable to other models in the same series?
2. Under what connection conditions were the IP rating tests conducted? What prerequisites apply to the wiring harness side for this rating?
3. Were the tests conducted using mass-produced wiring harnesses in a full-vehicle environment under full-power operating conditions? Were CAN bus error frames recorded during testing?
4. Regarding the insulation resistance specification: What are the specific values? Were they verified for each individual unit, or were they derived solely from sampling tests?
5. If water ingress is suspected during use, what information or materials does the warranty process require us to provide?

Suppliers who have actually conducted tie-down test verification will provide clear answers in their email responses; those who have not performed such work will often simply resend you a data sheet.

Frequently Asked Questions on This Topic

Is an IP67 rating sufficient for underbody installation?

If the connectors are properly seated and direct high-pressure water jets are avoided during vehicle washing, IP67 is sufficient for environments involving splashes, mud, and standing water. However, the IP rating alone does not tell the whole story; the installation method is equally critical.

Can a heater interfere with the vehicle’s network even while passing EMC (electromagnetic compatibility) testing?

Yes. Laboratory bench tests are conducted under specific conditions; however, long wiring harnesses, common-ground designs, and routing methods in real-world applications may cause issues that did not arise during bench testing. For this reason, full-power operational verification at the vehicle level is essential.

Does the IP67 rating cover requirements related to coolant leaks?

Not at all. This rating is used solely to evaluate the enclosure’s resistance to external dust and water. The integrity of the internal coolant, however, falls under a separate category of design and testing.

Are you reviewing the technical specifications for a heater? Feel free to send us the data sheet you’re evaluating—whether it’s from our company or a competitor’s. We’ll highlight the truly valuable information and filter out the fluff.