2019 GT Engine fan and A/C issues

[bwilder10h]

Hi all, I have a bit of a weird one I was hoping to get help with. My 2019 GT is not turning engine cooling fans or a/c on.
My a/c condenser took a rock late last year and I let it go until a couple weeks ago. I replaced it and went to charge the system earlier in the week and noticed the fans weren't turning on, nor would the a/c compressor kick on with the system up to pressure.
In troubleshooting, going through all the fuses and relays, checking wiring, etc, I noticed that fuse #42 (vehicle power 3) in the under hood fuse/relay box was blown. Unfortunately, when you replace and simply turn the ignition on, the fuse immediately blows and there is a pretty good pop. One time when I was testing the blown fuse was glowing which is something I've never seen before.
Oddly, I unplugged the engine cooling fan plug and the fuse does not blow. However, I have a spare fan from another project I was working on and it does the same thing, so I have to assume the issue is not the fan. Looking for any insights as to where to turn next. I don't have the wiring schematic for the car which would help but I'll be honest, interpreting those diagrams is far from my strong suit. Thanks!

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[Skye]

My a/c condenser took a rock late last year and I let it go until a couple weeks ago.

There could be countless reasons why someone lets something like this go. Unfortunately in doing so, it allows the atmosphere into an otherwise closed system. Moisture then begins to rust the parts in that loop. The same thing can happen to a home A/C system.

I do not have a specific wiring diagram to support t-shooting, but some general checks this morning note that fuse #42, vehicle power circuit three, is associated with three things:

- Active Exhaust (AE)
- Cooling Fans
- A/C Compressor

The cooling fans should turn on/off by themselves, given the appropriate temperature.

When the A/C is turned on, regardless of the radiator temperature, the cooling fans should also turn on; the logic behind this is to draw air across the condenser and help the A/C operate. The compressor, condenser and cooling fans help bring the refrigerant to the greatest density before going back to the car's interior.

Stating the obvious, the conditions you're seeing highlight a short circuit or a high load.

One t-shooting step is to disconnect the wiring going to the fans, disconnect the wiring going to the compressor. If you have AE, disconnect the leads attached to the valves at the mufflers.

Insert a new fuse into position #42. Start the car. See if the fuse holds. Then, connect the fans only. See how long or if that holds. Drive around, fans, only, to see if they continue operating as expected.

You could later attempt to re-connect the compressor, see what happens then. And later still, the AE valves.

The general idea is to disconnect all loads associated with the circuit, then re-insert them one at a time to identify the problem piece. If with everything disconnected the circuit continues to blow, that highlights a short circuit with the wiring itself, maybe with a connector end, maybe with a section of wiring damaged by something else.

Attached is a link to a web site which offers Ford procedures, the same that dealer mechanics use. It's $30 for three days, during which time you can download as much information as you like.

https://www.motorcraftservice.com/

Depending on the skillset, it might be worthwhile to seek out a local shop for an estimate. Pay them an hour of labor to t-shoot this issue and provide a general cost. The diagnostic fee is sometimes waived if they get the job.

Edit,

Thinking things out further...

Fuse #42 and vehicle circuit #3 is a 15A run. Fifteen amps isn't much to power the devices mentioned. And it doesn't. Vehicle circuit #3 acts as a trigger for high-amp devices. If you study the fuse chart, the fans, A/C compressor and other devices are powered by their own relays or fuses.

Fuse #42 is a low-power switching circuit, to latch the high-amp connections and those devices. It's like your home A/C system. You compressor is drawing tens of amps, but it could be switched by something as small as a watch battery in the interior thermostat.

As part of the t-shooting process, you'll want to remove fuses and relays associated with the fans, compressor and A/E valves. Doing so would help segment these issues further.

For example, disconnect the fans, compressor and A/E valves. Remove fuse #42. Remove fuses and relays associated with those devices. Insert fuse #42 only; You'd have a circuit with nothing attached as this point. Turn the car on and see if that holds. Later, insert the relay or fuse associated with the fans. See if that holds. Attach the fans. See if that holds. Drive the car to confirm the fans work as expected. Later, you use the same process to introduce the A/C compressor and the AE valves.

That's the general idea.

 

[SCP440]

A local AC engineer was telling me any A/C system left to atmosphere for more than a few months he would be scepticle that it will work again as is. moisture and foreign bodies can do a lot of harm in a system that is supposed to be clinically clean.
An AC system should be vacuumed out before fresh gas is installed as a minimum and if left open to atmosphere for an extended time I would suggest vacccum is applied for a couple of hours.

 

[bwilder10h]

Thanks for the replies. @Skye really appreciate the detailed response and suggested troubleshooting steps. I have a relay buddy and went through all the relays and the like yesterday. All of them test good, except relay 69 which I'm not sure would even factor in or not, however I ordered a new one and it should be here tomorrow.

Going through the steps you mentioned, when the fan and a/c compressor (and clutch) are unplugged, the fuse does not blow. Based on this, I would assume the issue is the fan, however I have a spare that I have here from another car and it does the same thing with it connected. I'm kind of at a loss given all things. Do we then assume there is a wiring issue somewhere?

Oddly, my car only has 2700 miles and because I purchased the motorcraft 72 diagnostic subscription you linked and it shows service history for the car, it looks like the previous owner had the dealer look at an issue with 1700 miles on the car and they replaced a wiring harness under the intake manifold. Or at least that is what I can gather from the vague write up on the site.

As it relates to the a/c service, you both are right that the system needs to be vacuumed down after a part was replaced and I did that. The condenser had a pinhole leak in it and when I replaced it, I vacuumed the system for 2 hours and it held good pressure. I guess the compressor could potentially be bad but right now it's completely disconnected and I'm just trying to get fans working so I can drive without it overheating. The a/c issue I can resolve independently... although obviously these two are kind of hand in hand right now.

 

[jheissjr]

- Check if relay 69 is related to the fans using the wiring diagram.
- Are the fan relays enabled when the fuse blows? If yes, which ones?
- What is the resistance of the three fans? Are they the same?
- Disconnect everything connected to the fuse. Relays, connectors, fuses, electronic modules. Use the wiring diagram to locate things connected to the fuse. Next measure continuity between ground and the downstream side of the fuse as you plug things back in. The short should show up.
-The wiring diagrams show how the electrical section of the fans works and the info is needed to troubleshoot the issue. Most importantly, download the wiring diagrams while you have access. Lastly, post the diagrams.

 

[Skye]

All of them test good, except relay 69 which I'm not sure would even factor in or not...

Going through the steps you mentioned, when the fan and a/c compressor (and clutch) are unplugged, the fuse does not blow. Based on this, I would assume the issue is the fan, however I have a spare that I have here from another car and it does the same thing with it connected. I'm kind of at a loss given all things. Do we then assume there is a wiring issue somewhere?

Relay 69 is associated with the cigar lighter and auxiliary power. If there are any auxiliary devices (dash cams, radar detectors, stereo systems, etc.) attached to the car, even if not associated with the circuits you're working on, I'd disconnect them while t-shooting.

I read the comments about the previous work involving wiring. 2019 with wiring work done at 1700 miles. Car has 2700 miles total now? Was the vehicle purchased directly from a dealer or through private sale?

For the car we're discussing now, the fans at some point were working as expected, yes? Did this fan issue occur because of the rock/condenser event, or did it start on its own?

The spare fan your plugging in during t-shooting, is it the exact same part as the original? That second fan is known good?

If installing the fan's relay and plugging in an exact replacement, known-good fan the circuit overheats or shorts, it does point to some upstream wiring issue, yes. Could be right at the very end, with the connector. Could be some of the previously-mentioned work is coming undone. A new issue. Or the original problem was never completely fixed. IDK.

The condition leaves one physically checking and inspecting, segment-by-segment, checking shorts and opens. I'm afraid I can offer any more detail than that.

You received some insight from the Ford site when accessing it. It reads like you might have come across some Oasis information.

When a car is under warranty and work is done, the work is recorded by Ford in an On-line Automotive Service Information System (OASIS). It'd depend on the dealer, but you might take what you have to them, to ask them to clarify, or, ask them for an OASIS report, so you can read anything that might have happened to the car warranty-wise before your purchased it.

In a previous thread, a GT500 was listed on offer. The CarFax/Oasis information highlighted multiple vehicle issues associated with electronics. The dealer bought the car back, replaced at least part of the wiring harness and offered the car for sale. If in a similar situation, maybe a supporting dealer could at least pull the file on the car and read out to you what was accomplished prior.

Something, some key word or phrase in those documents might help you towards zeroing in on this problem.

 

[SHOdaddy68]

Are you charging the system yourself? Your car takes the new R1234YF refrigerant. Hopefully you didn't try to put R134a in it.

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