2013 Fiesta blower motor (power to relay coil)

Hello. My friend has a 2013 Fiesta. The blower motor recently quit working. As time and weather permits (seems it’s rained all summer so far) I’ve been trying to figure it out. Here’s what I’ve done so far.

The car has the standard control head with no display. Does not work on any speed, heat or AC. Kinda rules out the resistor.

Turning the fan on and off or changing speeds does not make the relay click. Relay tests good, clicks with battery voltage and has continuity across terminals during that time. Switched side of relay socket has 12v available at all times.

Also checked cooling fan relay which was right next to it and it tested the same. Swapped them with no difference.

Blower fuse is good.

Pulled connector from blower motor, and no voltage at connector with ignition on and blower control on, any speed.

I did all this last week. Today in the rain I had to fix a coolant line so I checked some more things.

I bridged the switched relay terminals to fake the relay being on. The blower motor ran like normal on all speeds, operated by the control head.

So I checked the voltage at the relay coil with the key and blower control on. Across the terminals started at 7 volts, and gradually dropped to 5 volts. By then I gave up, it had slowed but was still slowly dropping. Then individually to the battery, the power side was a little higher by 100-150mv. The ground side had about 100-150 mv. Not sure if this is proper, but it was barely a drop in the bucket. Isn’t this supposed to run at 12v? That would explain why it’s not enough to fire the relay coil.

So without a schematic, what’s next to check? Where does the relay coil power come from and how do I check it? BTW, the cooling fan relay is right next to it, and that runs fine. It was running today.

The line from the Blower Relay to the BCM or to the Controller (More than likely the controller) - you'll need to do a continuity check on it.

Notice the "two Ground wires" running from the Controller - look for those in two places, under the dash bolted to the firewall just above the Brake pedal and or the ones on the Floorboards under the carpet by the Front Seats.



These are for the MANUAL Climate Control System.

In order for the Relay to find a way to power it, you verified by the jumper, the blower works, so if the Relay checks good (you swapped it out with another known good relay) then the controllers wiring harness side and it's grounds are the next to check.

Thank you for the diagrams and tips. Basically it’s the blue/gray wire going to the relay coil not getting enough voltage. Whether or not it’s low coming from the central junction box, or if it’s something in the control module drawing it off, is what I plan to figure out. By pulling the control module and testing the wiring, also the grounds you are referring to.

I was planning to look at that tomorrow, but today it blew the head gasket. Badly, like cranking the engine blows coolant out the reservoir. So looking at options, whether or not to fix it and possibly having a cracked or warped head to deal with, or drop in a good used engine for $350 and change the timing belt for good measure.

I’ve done all sorts of things including engine swaps, but the bulk of my experience is in 1989 era FWD GM cars.

Edit: Gonna start a new thread for the engine problem.

Everything still looks good with the engine, so today I got back at the blower motor relay circuit.

I pulled the control head and the glove box. Volts tested good at the head. Volts also tested the same at F21 in the central junction box. So that means it was something between S228 and the battery junction box. Maybe S213? But don’t know where that is. I took apart the battery junction box and no problems with the terminals or wiring inside.

I’m guessing C210 was the massive connector at the base of the drivers door held together with a 10mm bolt. I opened and reseated it and tested every blue/gray wire, but couldn’t find anything definitive.

So I ran a new wire from the control head to the relay coil terminal in the battery junction box. Went tightly through one of the rubber plugs in the firewall to avoid leaks. Now it tests great with next to no resistance and the blower motor works perfectly.

I disabled the old wire at the battery junction box. I didn’t disable it inside the car because I wasn’t sure where S228 was. If I can find that, I will disable more of the old wire. I’m guessing it was just a bad connection. If it was shorted to ground, I’d think it would have gotten hot or blown F21. Especially like today, it was down to about 1 volt by the time I was done testing before disassembling things.

Also cleaned the MAF. That made the check engine light turn off.

The box itself has jumpers that snake thru the plastic to feed - so you see the bluestripe wires but can't locate the break? That may be a loop inside the harness as the bridge used between the junction box to the connectors.

Good job in just running a spare wire to get the blower working again, to me this sounds like a loop of wire that broke at the joint in the wrapped part of the harness at the tie or curl. That happens the AWG of wire inside it pretty thin and the copper wicks up water so it corrodes thru the strands - so this is also a heads up you may find issues at a later time in that harness as fails are likely possible and also be sure it's not getting dripped on by the battery acid or left to shake dangling on a wire tie.

Thanks for the tip about the internal folds and jumpers. I wasn’t about to tear that whole harness apart, but I would if I really had to. It’s anchored well but I did try yanking on it all which ways and couldn’t get the voltage reading to improve. No battery leakage and the car is surprisingly clean and mostly free of rust and corrosion.

I spent the afternoon on it, hoping I wasn’t gonna get rained on. Story of my life in Michigan. Garage is occupied now. Thinking about it later, I only tested from the control head to C210. Didn’t test from the battery junction box to C210, maybe that would have helped me ID the wire depending on where the break was. I can always test and see if voltage is being lost again, that’s quick and easy.

But I’m glad to be done with this car for now. Got a lot of my own stuff that’s been put on the back burner and summer will be over soon.