When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
You definitely have something wrong affecting both speed settings.
You are referring to low fan in singular, so I'm not sure if you know that in each speed setting both fans are supposed to run at the same time.
There are 2 fan circuits:
Low Speed (½ the speed) - fans configured in a Series Circuit where ½ the voltage is applied to each fan.
High Speed (full speed) - fans configured in a Parallel Circuit with full voltage to each fan.
These are the schematics with the current path superimposed for each speed setting to help you troubleshoot your problems.
As you can see, Fuse 46 is only part of the equation when in High Speed mode and should only affect the right fan.
Since the Low Speed mode is configured as a Series Circuit, any interruption along the current path should affect both fans.
On the other hand, in a Parallel Circuit it's possible to have none, both or either one.
I'm including here a description of how fans are commanded, so you can compare it to your car.
NORMAL fan operation on a C5 is as follows:
Low Speed - Triggered when coolant temperature reaches 226°F. When the coolant temperature drops to 219°F then the fans are turned OFF.
High Speed - Triggered if the coolant temperature rises to 235°F during low speed operation. When the coolant temperature drops to 226°F then the fans drop back to low speed.
With AC turned ON the cooling fans come ON in low speed mode when the coolant temperature is about 185°F. The fans remain ON in low speed mode until coolant temperature reaches 235°F, then they go into high speed mode.
If the vehicle speed exceeds 35MPH the PCM turns OFF the fans regardless of the coolant temperature. Air flow through the free-wheeling fans should be enough to keep temperatures within parameters, as long as the radiator fins are not plugged up. If they are plugged up, then the coolant temperature will rise and the fans will NOT come ON unless the car goes below 35MPH.
Thanks. I have already seen your helpful marked up wiring diagram, but cannot find any potential one thing that would cause all my symptoms. I am aware that both fans should always run together either in high or low.
Left fan always works on low, right fan sometimes does not even when left fan is working, neither fan works on high, left or sometimes both fans work with A/C on with cold coolant.
...Right fan is apparently intermittent, but does not explain no high fan...
...Found Fuse 46 blown and replaced...
Originally Posted by wrmiles
...Left fan always works on low, right fan sometimes does not, even when left fan is working...
@wrmiles : I suggest you should begin troubleshooting here. The Low Speed mode has a simpler current path with less components involved and since it's a Series Circuit it will allow you to narrow things down a little.
You mentioned that you found Fuse 46 blown. Since current only flows through this fuse for "Right Fan-High Speed", and the only components downstream Fuse 46 while in this mode are Relay 43 and the right fan itself, it's very possible that the overcurrent that blew the fuse was caused by the right fan.
If the overcurrent was caused by an internal short in the right fan while in High Speed mode, that would explain why in Low Speed mode the left fan still works while the right one doesn't. Otherwise, since this is a Series Circuit, it would be a case of "both or none".
There's also the intermittency aspect to complicate things further, but you need to do some troubleshooting first to be able to move forward.
Using a multimeter, could you take a reading of the voltage across each fan (from A to B in the schematics, NOT from ground) while in Low Speed mode when the left fan is running and the right fan is not?
Thought I would post a followup after getting car out of shop (independent shop not specializing in Corvettes) and taking a road trip to central California, where it was pretty warm.
Both fans worked on low when activating with scan tool, but right fan did not when temp reached 226, confirming intermittent problem possibly aggravated by heat. Replaced right fan motor (it was previously replaced about 4 years ago and replaced on warranty a year later.)
Shop could not confirm neither fan coming on high (story is a little unclear). Replaced both high fan relays.
Cleaned radiator fins. Needed it pretty bad.
Everything normal per my experience on road trip. Never got hot enough for fans to come on high.
Weird Radiator Fan Problem
