Heat and Overheating


The boxed numbers and the letter “S” to the right of the Overheat Value represent the unit’s heat scale. When a unit overheats, the amount by which it overheats is added to the unit’s heat level, which is then marked on the heat scale.

A unit’s current heat level will be added to its weapon attack target numbers, and twice its current heat level (in inches) will be subtracted from the unit’s ground movement rating. (Jumping Move is not affected by the heat scale.) Heat scale levels should be marked in pencil, as a unit’s heat will rise and fall throughout game play.

Remember that heat levels do not actually change until the End Phase of the turn in which the unit overheated. Thus, modifiers caused by overheating do not impact the attack that causes the overheating to begin with; they will instead affect the unit during its next turn.

Heat (HT#/#/#) Special Ability: The Heat special ability reflects units that are capable of raising a target unit’s heat via outside heat sources (such as flamer weapons).
In a single turn, no unit may receive more than 2 points of heat from attacks made using this special ability. If a unit capable of building heat has already generated 2 points of heat during the turn from HT#/#/# attacks, the unit does not receive any additional heat effects; instead, the extra heat points from these attacks are simply lost.

Shutdown: The maximum heat level of 4 appears on the heat scale as an S, which represents automatic shutdown. A unit reaching this level on the heat scale shuts down, and cannot expend Move or Thrust, or execute any attacks in the following turn. If the unit contains any special electronics (such as ECM), that equipment will also stop working wile the unit is shutdown. While shutdown, a unit is rendered immobile. As such, it has a target movement modifier of –4.

Aerospace Units: Aerospace units that suffer shutdown must consult the Aerospace End Phase rules in the Abstract Aerospace System chapter.

Cooling Down: Any unit that used Overheating in the current turn will increase its Heat level as mentioned above, and thus will not cool down at all in the End Phase.

If a unit outside of water (or in water terrain of less than 2 inches in depth) made a weapon attack in the current turn—but does not use Overheat—its Heat Level will remain
unchanged in the End Phase. A unit in water of 2 inches in depth that used only 1 point of Overheat will also not change its current Heat Level in the current End Phase.

Heat levels will thus decrease during the End Phase only as follows:

A unit that begins the End Phase as a shutdown unit automatically drops to a Heat Level of 0 (and restarts). A unit does not make a weapon attack in the current turn
also reduces its Heat Level to 0.

A unit that enters water of 2 or more inches in depth will reduce its Heat Level by 1 point, as long as it did not use any Overheat in the current turn.


Overheating: Many ’Mechs and some aerospace units have an Overheat Value (OV) shown on the unit card. This number reflects the fact that these units have more weapons than they can safely fire. A warrior piloting such a unit can push it beyond its safety limits to inflict extra damage. However, the heat build-up caused by such action will slow the unit down and cause its targeting systems to behave erratically until the ’Mech has a chance to cool off.

Using Overheat Value: An attacking player must announce his use of Overheat Value— and how many points of OV he wishes to use—before resolving the attack’s to-hit roll. A unit with OV can apply anywhere from a minimum of 0 OV points to a maximum equal to the unit’s OV rating. If the attack succeeds, it deals extra damage at the Short or Medium range brackets equal to the OV points used when the attack was announced.

For each point of Overheat Value a unit uses in this fashion, one point of Heat is added to the unit’s Heat Scale. If the overheating unit is in water, it reduces this heat level by 1 point.

Special Ability Damage: Special abilities that deliver damage (or heat) effects (such as ARTX, FLK, HT, IF, LRM ,REAR, SRM, TOR, and TUR) may not be augmented by overheating. Physical Attacks: Physical attacks may not be augmented by overheating.

Overheat Long (OVL) Special Ability: If a unit has the OVL special ability, its use of Overheat will also increase its damage value in the Long range bracket in the same manner as it will for Short and Medium range.

Heat and Overheating

McKinnon’s Raiders Ziekx