Unless "slow" is all it can do when "high" is selected, that doesn't sound like a fan problem.Ya mine is only running on low speed similar issue.
I don't think it's the fan. I'd suspect one of the relays. I think 3 are plug-ins in the underhood fuse box, but the other two are soldered in on the underside of the fuse box.No, mine works on low. When high is selected it does nothing. Thanks for the schematic Doug.
That's weird. "high" bypasses all resistors and applies power straight to the fan motor. If it was a bad motor, I'd expect it to limp on high and not function at lower settings - not the other way around.The relays have all be verified already. When it is calling for low speed the fan turns slowly. When calling for medium it won't turn unless I give it a push. Then on high it won't budge but there is voltage across the terminals to the fan. I suspect you are right that the fan motor isn't finished but it is one of the resistor packs you mentioned earlier. Since they are built into the fan assembly and cannot be changed then the fan assembly has to be replaced.... Was able to get one for $100 not too bad.
Indeed. It looks replaceable, but it's hard-wired in and sold as part of the fan.From what I've read the resistor bank is built into the fan assembly past this connector.
I'd be curious to see what's in your manual - I could have missed something. I had the same thought about using a 3rd ECM pin. I don't want to pick on GM - they have some pretty sharp folks there - but it does seem klugedYour chart doesn't agree with that I'm seeing in my 2013 manual.
But to answer why 5 relays - 3 large relays are used to send power to one of three terminals that control the fan speed (resistor pack). The other 2 relays are used to decode the 2 outputs of the ECM into 3 speeds + off. Not sure why GM felt they had to save a pin on the ECM. Fortunately, this kluge seems to rarely be a problem. It's usually the resistor pack.
Completely forgot to post the outcome on this. I replaced the fan and it works great now on all speeds. After topping up the coolant from the loss through the overflow when the fan wasn't working I also had to replace the o-ring on the overflow cap as it was leaking by when the engine was warm. Running great now 172,000 Km hopefully many more.