Repairing the smart ED3 PTC heater


Nevertheless, electric cars are vehicles with up to 400V on-board networks, some even up to 800V. It is a great advantage to know what that means: Even if there are a lot of safty features in the car, incorrect handling can endanger life. It is always advisable to visit an experienced workshop whose employees have a HV certificate to work on high-voltage components. For private individuals, this is only at your own risk.

Before working on high-voltage components, always pull the service disconnect. This reliably de-energizes the high-voltage system. All high-voltage cables are clearly identifiable as these thanks to the orange plastic sheaths.

Quick overview

Roughly speaking, you have to remove the heating element in order to open it and re-solder some contact points. A loose contact may develop over time, as the heating element warms up regularly and then cools down again. This is fixed by soldering these points. Otherwise, as a result of the loose contacts, one or more of the 10 heating coils in the heating element will fail.

The vehicle itself does not give any useful errors, if it gives any errors at all. The repair isn't perfect as the soldering points could break, but it's inexpensive and nothing else can break. In my experience, this fixes the problem permanently. Nevertheless, the implementation is of course at your own risk and I give no guarantee on the statements made here.

In order to avoid control units storing error messages that cannot be erased, first of all disconnect the 12 V battery. This can be found under the carpet and styrofoam in the right footwell. This way we avoid annoying errors in the control units and a visit to the workshop to delete them.

The vehicle's HV system must then be deactivated. Pull out the red plug next to the fusebox in the left footwell. This is reinserted at the very end until it makes *click*. But only when the 12 V battery has been reconnected.

If the factory navigation system then requests a code, there is a very high probability that it will be "0000".

Das PTC-Heizelement des smart ED3 reparieren

Find and remove the heating element

The heating element can be found in the passenger footwell on the left-hand side. To reach it, remove the doormat and the styrofoam. Just like you do if you want to swap the 12 V block. The heating element can now be found on the left.

Das PTC-Heizelement des smart ED3 reparieren

First of all, unplug the orange HV connector. To do this, press on it at the top and bottom so that it unclips and you can pull it to the back. Then unplug the CAN connector, first unlatching it using the gray contact. Now uthe three screws that hold the heating element itself in place must be loosened. After all this is done, remove the ground cable.

The heating element can now be pulled lengthwise, horizontally out of the shaft.

Open the heating element and re-solder

How to get the necessary circuit board is relatively self-explanatory. That's why I won't go into it step by step now. After loosening the screws all around, you should carefully open the cover and detach the CAN connector from the circuit board. Then you can also remove the HV connector and the associated interlock connector from the board. The upper circuit board must then be loosened and removed together with the black frame. Now it should look like this:

Das PTC-Heizelement des smart ED3 reparieren

The circled contacts must be resoldered. These are contacts for an IGBT module by Infinion. If these do not make contact, the heating coils are not activated and the heating element also won't work as a result.

After they are soldered, the heating element should work again. Now everything can be reassembled and finally the Service Disconnect can be installed again.