Ford — Lack Of Heat Diagnostic Test
Testing & diagnosis · HVAC heater core
From a Ford service manual — check it applies to your exact model before use.
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Procedure
- Confirm the vehicle has a lack of heat from the vents when operated consistently below -20°C (4°F) and is equipped with a block heater.
- Run the engine until it reaches normal operating temperature. Select the floor position, temperature control to full warm, blower to medium.
- Increase engine speed to 3,500 RPM. After 30 seconds, allow the engine to return to idle for an additional 30 seconds.
- Measure the heater core inlet hose temperature. Is it above 66°C (150°F)?
- Measure the heater core inlet and outlet hose temperatures. Are they within 6-17°C (10-30°F)? If not, proceed to repair.
Tools required
- suitable temperature measuring device Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 66°C (150°F)
- 6-17°C (10-30 FridayParts $28.40°F)
- 3,500 RPM
Source: Ford service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.