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Hvac System Error 21


Tyler121

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Just guessing but if you didn't have a light shining on the sunlight radiation sensor the diagnostic will stop there showing it as a failure. Holding a shop light above it usually gets you past that "fault".

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From '92 LS400 shop/repair manual.

Code 21 is the solar light sensor ciruit.

22 is "locked" compressor.

23-30 not used.

31 is open/short in the reheat/remix damper position sensor circuit.

32 is open/short in the air inlet (fresh/recirc.) damper position sensor circuit.

33 [a] open in reheat/remix damper position circuit, or...

33 open/short in reheat/remix damper servomotor circuit, or....

33 [c] Remix/reheat servomotor "locked"/stalled.

34 [a] open in air inlet damper position sensor, or...

34 open/short in air inlet servomotor circuit, or...

34 [c] air inlet servomotor locked/stalled.

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well i don't have a shop light but if i do it outside should it bypass 21? or do i need to go up to my neighbors and use his light

BRIGHT sunlight or flashlight....

What is your reason for testing...??

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