Auxiliary Water Pump Not Working

[SocalD]

Hey all! I have a 2005 4.8is and my relatively new auxiliary water pump is not working. Quick history, last year I had the common problem where my AC System (IHKA) would shut off, no power. Turns out there was debris in my water pump keeping the impeller from spinning and causing an overload on the shared 5A fuse with the IHKA. I replaced the water pump and was working fine, no more blown fuse! Now, a year later, the pump is not working. I found this out when replacing the coolant and during the "bleed" process, I could not get the pump to activate. I used my "DIS version 57" software to turn on the pump and nothing. I then disconnected the power leads to the pump and they read 4.3V constantly whether the pump was turned off or tried to turn on with IHKA controls or DIS software. There was once where I briefly saw 12.5V but only for 1 second. Couple of questions: 1) Does the IHKA system power the pump directly or is there a separate relay for the pump? 2) If the IHKA does power the pump, is it simply on/off @ 12V or does it using varying voltage/PWM to vary the speed? 3) Does it sound like I have a bad IHKA module?

[andrewwynn]

I believe it's a brushless motor that you can apply DC to have it spin just make sure you have the polarity correct.

If you can run the activate command from software you should be able to see voltage but check the 12v to chassis ground as many systems on this car are controlled from the ground side.

Also, you can use AC voltage on DMM to test for PWM (mine will also show duty cycle) in case the brain is trying to control speed that way.

[SocalD]

Thanks Andrew. How do I check the voltage to ground? Do I put the positive lead from my DMM on the connector for the pump and then the negative DMM lead to the chassis ground somewhere?

[andrewwynn]

Correct. Once you confirm polarity you can direct drive the pump to confirm it works. I have a bench power supply and tested mine on it and it ran from 12-14 DC