So I'm going through and checking out the fan control system to ensure the fan is kicking on when its suppose to after having an episode last week while sitting at a stop light and the temp gage went beyond where it normally goes. The fan didn't kick in and after rolling at 35 to 45 mph, the temp came down. Which tells me the circulation system is working OK. I go home, sit in the shop with the car idling, temp gets up, the fan kicks on, temp come down, fan shuts off, all appears normal. Intermittent issue?? So I decide to do some electrical troubleshooting. I find the on and the high/low relays, pull them out of the sockets, short out the appropriate socket pin according to the diagram in the service manual, and manage to get the fan to kick on, both low and high speed. I proceed down to the PCM, pull the gray plug that has the two control pins for the relays (2 and 21), and short pin 2 to ground. Fan comes on at low speed. Good. While holding the ground on that pin, I short pin 21 to ground, which is suppose to switch the high/low relay, thus kicking the fan into high gear. It stays on low speed. Then here is where it gets weird. I disconnect my test wire from the chassis ground and simply short the two pins together (2 & 21) and fan kicks in to high gear! ***!! Doesn't make sense. Has anyone ever delve this deeply in to troubleshooting their cooling fan circuit that would have any clue why this is behaving this way? I plan on ohming out the whole circuit this weekend that hopefully will shed some light on what's going on as well as testing the relays out of circuit with an ohm meter and 12 volt power supply but this is going against all electrical logic according to the electrical diagram in the book.
BTW, there is plenty of coolant, both in the overflow tank and the upper reservior.
Also plan on running the vec 3 software through the vec 3 as I believe there is a sensor monitoring real time data stream feature that will allow me to monitor the coolant temp sensor and compare it to the temp gage reading just to make sure the gage is reading close to right.
BTW, there is plenty of coolant, both in the overflow tank and the upper reservior.
Also plan on running the vec 3 software through the vec 3 as I believe there is a sensor monitoring real time data stream feature that will allow me to monitor the coolant temp sensor and compare it to the temp gage reading just to make sure the gage is reading close to right.
