XXXLTRP

It's running a little hot. The coolant temp rises until the high speed fan kicks in...cools back off when I drive, but it heats back up when sitting still. The low speed fan isn't kicking on. I've looked at the owners manual, fuses 49 (cooling fan 1) and 46 (cooling fan 2) are associated with the cooling fans, I pulled both of them and they are both ok. Relays 43( mini relay cooling fan 2),44 (mini relay cooling fan 3), and 45 (mini relay cooling fan 1) are also associated with the cooling fans. I didn't pull those as I have no way to tell if they are bad.

I pulled the codes...

40 BCM
B2578 H ...right turn signal
B2583 H ...another turn signal

BO RFA
U1096 H...loss of communication with IPC
U1064 H ..loss of communication BCM
U 1016 H ...loss of communication with PCM

I only have 2 fans, so the relays are a bit confusing. There are three relays but only two fans. When facing the car from the front, the only fan that kicks on in high speed is the one on the passenger side.

Should both fans cut on in high speed?

Should both fans cut on in low speed?

Is the fan on the drivers side bad?

Relay bad?

Any idea which relay is associated to high speed fan and low speed fan?

Thanks for any help!

XXXLTRP

I reset all the codes, same problem.

lucky131969

The attached link contains the schematic. Since only one fan is running in high speed, and neither is running in low speed, you may have a bad fan. In low speed, the fans are in series, while in high speed, the are in parallel. I'll pm you my number if there is something you don't understand.



http://forums.corvetteforum.com/c5-t...y-come-on.html

XXXLTRP

After reading the posts in that link, it appears that the one fan that is working ( passenger side facing the car)..is working in low speed. It hasn't gotten hot enough to command the high speed fan/fans on based on those temp ranges.

Does that change anything?

lucky131969

So the right fan is the only one working at low speed? That tells you that Relay 45 is engaging(low speed fan control from the PCM), relay 44 is not engaged...and that G102 is providing a good ground for the right fan motor. Strange that the left fan is not functioning, but allowing current to flow without blowing the fuse.

XXXLTRP

I went back out to mess with it some more. I put the AC on to lower the temp that commands the low speed and high speed fans...and it worked just like it's supposed to. Both fans cut on low speed at 185 and both went to high speed at 194.

So I turned the AC off to raise the temp that commands the low and high speed fans. Both fans went on low speed at 226 and back off at 219....I can't get it hot enough now with the AC off to command the fans to high speed.


Fixed?

Yesterday was the first time in a while it has gone far enough to reach 226 degrees and command the fans to kick on. With the cold air temps and my short trip to the gym, I doubt it reaches 226. I'll be keeping a close eye on the digital gauge to see what happens.

Maybe it was having a finicky day yesterday.