Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

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Ambient Temperature Sensor / Switch HVAC: Testing and Inspection


1. Remove ambient sensor and check resistance using a suitable ohmmeter. Do not hold sensor in hand or apply ohmmeter current for more than 5 seconds, or sensor resistance and resistance reading accuracy will be affected.
2. With an ambient temperature of 70 to 80°F, sensor resistance should be 255 to 335 ohms.