A/C control unit wiring diagram needed?

BHAMDOC1973

MEMBER
2005 LEXUS RX 330
V6
2WD
AUTOMATIC
240,000 MILES

Which wire or color on back of A/C head unit should have power when ignition is on? No response at all from unit so I want to check ground and power.

Monday, September 2nd, 2024 AT 7:03 AM

3 Replies

KEN L

MASTER CERTIFIED MECHANIC
47,602 POSTS

The Heater fuse (7.5 amp) in the interior fuse panel is the only fuse out of the four that have power when the key is on, the other three stay hot at all times. Here are the other fuses and a guide to help check for power and to see if the fuses are any good or not.

https://www.2carpros.com/articles/how-to-check-a-car-fuse

Also, I have included the complete HVAC wiring diagrams so you can see how the system works and where the power and grounds are. Check out the images (below). Please let us know what happens.

Images (Click to make bigger)

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Monday, September 2nd, 2024 AT 12:23 PM

BHAMDOC1973

MEMBER
1,573 POSTS

I used a probe to check for power and ground, all have it, I tried to probe the wires with + just to see if giving them power would make the HVAC unit come to live and one of them did get the blower to go. So even after putting back everything the blower still work with the button at different speeds and you can change to defrost, but none of the lights come on no matter what u chose, couldn't get the compressor to kick on, so that's good enough I'll sell it like it is. Thanks a lot.

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Monday, September 2nd, 2024 AT 12:51 PM

KEN L