This 1999 Lexus came in with the complaint that the engine cooling fans would stay on even after the key was turned off. The customer stated that they stayed on for an hour or more and she had to disconnect the battery to keep it from going dead. I figure that there was a relay sticking so I took a quick look at a component locator and found that there were several relays listed for the cooling fans. I pulled each one that was listed and no single relay would turn both fans off.
I decided to look at the wiring diagrams and honestly they wire quite confusing because there was actually no way according to just the cooling fan diagrams that the fans could turn off. I dug a little deeper in the diagrams to find out how the listed cooling fan relays were supplied power and ground. In the power distribution diagrams I found that there was an engine main relay listed that had to be the problem. I am pointing to it in the picture below.
I removed the relay and both cooling fans stopped at the same time. I also noticed a slight bit of soot on the white plastic.
I removed the cover from the relay and sure enough the contacts were stuck together and there was a lot of soot.
I tried to break the circuit by applying pressure to the hinge spring but that did not work.
I then used my pocket screwdriver to separate the contacts. I also use the tip of the screwdriver blade to clean the debris from the contact. This enabled the car to be driven again until I could order a new relay from Lexus.
Just a picture of the soot inside the relay cover.
I inserted my pocket screwdriver blade as shown below to release the retaining clips for the cover and repeated on the other side.
A picture of the relay with the cover successfully removed.
This picture show the part numbers on the relay. 85925-17010 and 056700-7770, one number is a Toyota part number and the other is a Denso part number.