Start heater operation, function

Initializing

The electric heater's power regulator switches to a specific status with deactivated PTC heater sections after ignition terminal 15 is switched on. The power regulator starts to evaluate the input signals after a waiting period of 0.5 seconds after terminal 15 ON.

Function

If the input signals display a maximum heating capacity request (MHR = Max Heat Request) and the heater booster is enabled by the engine management (MM) with a logical LOW, the PTC heater booster stages are switched on. In all other instances the PTC heater booster stages remain switched off.

Instantaneous heating

An "instantaneous heating" feature has been integrated in order to achieve heating output by the PTC heater booster as quickly as possible after switching off the PTC heater booster by the engine management (signal level MM = 1) and then enabling it again by the engine management (signal level MM = 0).

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 If the PTC heater booster is enabled again by the engine management (MM = 0) the 1st section is immediately switched on, if the current generator capacity utilization status (DF-value) is less than the generator capacity utilization stored at switch off (MM = 1) (without any time interlock) and at least one PTC section was switched on at the time of switch off.

 In the event that when the PTC heater booster release was switched off by the engine management (MM = 0) there was no activated PTC stage present, the "instantaneous heating" feature is not activated.

 The "instantaneous heating" function is reset when the heating power request signal from the heater control module or the air conditioning control module goes away.

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Performance at undervoltage

The voltage is measured between terminal connection 15 and terminal connection 31 (ground).

The power regulator is equipped with an undervoltage detector. If a battery voltage of less than 11.5 V  1.2 V is detected which lasts longer than 0.5 seconds, all heater sections are switched off.

The cut-in threshold for undervoltage conditions is 12.0 V  1.2 V.

After an undervoltage is detected all stages are switched off in a time span of 50 ms one after the other.

The heating sections can be switched on again only after the undervoltage condition has been cleared.

Performance at overvoltage

The voltage is measured between terminal connection 15 and terminal connection 31 (ground).

The power regulator is equipped with an overvoltage detector. If a battery voltage greater than 17.2 V  1.2 V is detected that lasts longer than 0.5 seconds all heating sections are switched off after a maximum period of 6 seconds.

The cut-in threshold for overvoltage conditions is 16.7 V  1.2 V.

The heating sections can be switched on again only after the overvoltage condition has been cleared.