Johnson CM90 Pump
Thread Starter
Super Member
Joined: Dec 2007
Posts: 504
Likes: 8
From: DE
2003 E55 AMG
Johnson CM90 Pump
Here is the deal. I'm having problems with my IAT temps. They are in the range of 120-150 when cruising with 70mph. A lot of people over here are sure that my IC pump is bad. I got under the car today just to find that it is fitted with Johnson CM90 Pump. Here is the issue. That pump is wired with a relay. There are 4 wires going in and out of the relay. IN(big red + always on ) IN (red/oragne + ) OUT(red wire going to the pump +) and IN black wire. The relay is grounded to the chassie with another black wire that goes to the pump - .
When i turn the key to pos.2 the pump is not working. When i turn the car on the pump is not working. When i energize the pump directly from my battery to the pump it is working. Not sure if it is working at maximum output but it works. Also when i energize the relay for the Air Pump via my scan tool the pump starts to work. I'm not sure what is going on here. Is this pump supposed to be on all the times??
When i turn the key to pos.2 the pump is not working. When i turn the car on the pump is not working. When i energize the pump directly from my battery to the pump it is working. Not sure if it is working at maximum output but it works. Also when i energize the relay for the Air Pump via my scan tool the pump starts to work. I'm not sure what is going on here. Is this pump supposed to be on all the times??
MBWorld Fanatic!
Joined: Mar 2011
Posts: 1,879
Likes: 22
From: Orange County, CA.
one car at a time
Sounds like you either have a bad relay or connection...If the connections are all good, you could just grab the relay number (from the relay) and replace...Or as Munich pointed out you could run a 12+ ACC to the pump and be done with it....Just make sure the power is not 12v+ constant or your battery will die quickly (after you park your car)....
