No Cooling

[calvinhc]

So just as the weather is finally getting warmer, I went out yesterday on a short (1-1.5 hour away) road trip. It wasn't super hot (about 24C/75F), but I thought using the A/C with windows shut would be better for range and no A/C with the drag of open windows.

The air blowing was just not cooler, which took a bit to be sure as blowing air feels cooler and the temperature was not super hot, but more noticeable was that the guess-o-meter did not change. Given that the system may have decided that with the outside temperature, the cabin setting may not have been an additional load on top of what it was doing for the battery and motor already. Having gone through the replacement of one of the two coolant diverter valves about six months ago, I thought that the other may be having an issue, though no wrench light came on. Not having A/C was not a problem this day, until I got to my destination and had to charge.

I planned on bringing up the SOC to about 50% on a DCFC and moving to a level 2 charger for the duration of my stay (about 2-3 hours) to fully charge for the return trip. The DCFC, rated at up to 50 kW, started off delivering 35 kw, which is not unusual for the network it is part of in my experience. But then about 10 minutes in, it started to drop an it got to 16 kW before I stopped and moved to the L2 spot. The SOC started at 26% and got to 41% before I stopped. The L2 was delivering 5.7 kw, which didn't surprise me with this same network which is what they typically deliver on an "up to 7.5 kW" unit. However, I noticed a couple of hours later it had dropped to about 4.5 kW.

When I returned and started to leave, I got a warning with the "turtle" light in the dash (first time I've seen that) indicating that performance may be limited due to a hot battery. What I was suspecting was pretty much confirmed: the compressor was not coming on. The only cooling available was the coolant circulating pump and the radiator fan.

It was getting cooler when I left and the airflow from being back on the highway must have done a half-decent job of cooling things since the guess-o-meter had my surplus to get home gradually raise from about 40 km when I started the drive to about 85 km about a half hour before getting home. It would be nice if there was a way to see battery/motor temperature on the dash - my wife's Lightning has a battery and motor temperature indications at the top of the dash display (bar style, not actual numbers).

Once home, I connected the laptop and fired up Forscan, but there were no DTCs whatsoever. I noticed it showed that the AC_PRESS_HI and AC_PRESS_LOW sensors were reporting pretty close to the same values - about 153-156 kPa for the high one, and 157-158 for the low one. I hadn't looked at these when things were working, but I suspect that the high pressure sensor should be noticeably higher than the low one.

About the only thing I have the ability to check was the functionality of the high voltage fuse for the compressor that is located with the TCM - no problems there. So, I'm guessing that either the coolant leaked out and it won't start because of that, which would not just involve getting it topped up but also finding the leak, or that the compressor itself is shot and needs replacing.

This will be going in to have it looked at, but I'm curious if anyone has any other suggestions.

[Anti_Climax]

Under normal operation, the high side would be something like 5x the pressure of the low side but when it's off, you expect them to equalize.

That low pressure is lower than you'd expect while it's cycling and you'd expect them to average out when it's idle. It's not a straight linear relationship so you don't expect it to average 2.5x the low value but you expect it to at least be noticeably higher.

My money is on low refrigerant. I do recall that when I had my refrigerant leak, the compressor would not start without sufficient pressure and if it's not running you will not get battery cooling. When the coolant passes 97F it will close the battery loop to cycle through the chiller, but without the compressor it's just circling the hot coolant right back into the battery.

Forcing the diverter back open would possibly let it operate longer before getting too hot, but any relief the radiator can offer is going to be offset by the coolant going through the motor.

[calvinhc]

My money is on low refrigerant. I do recall that when I had my refrigerant leak, the compressor would not start without sufficient pressure and if it's not running you will not get battery cooling.

Thanks for the explanation - the more I look at this, the more I'm inclined to agree it is likely low refrigerant.

I'm thinking of recharging it myself - I can get a recharge kit by AC Pro that has the R-1234YF refrigerant that my 2017 FFE uses. It also contains a leak sealer which would be helpful for any minor leaks that lead to this.

I'm wondering if adding lubricant would be recommended. Some things I've read indicate this is not necessary if no components of the cooling system have been replaced, but I'm wondering if lubricant can be lost when refrigerant leaks out. I'm thinking that the refrigerant leaks out as a gas and does so through fairly small leaks that are not likely to leak a lubricant, but I don't know for sure.

I do know that the correct POE lubricant is needed, that is not the type used in ICE Focuses.

[Heima]

I do not know what the "resting" pressure of the refrigerant, but the values shown in forscan are just over ambient (100Kpa).
At 65F, the low pressure side of a functional auto A/C unit is 175Kpa and the high pressure side is 950Kpa. So the resting pressure should be something in between. As the ambient temperature goes up, so do those pressures.
So I am thinking that it is a leak as well.

Recharging might be only a temporary solution. You really need to check for leaks. If the recharging kit has a dye injector, consider spending for that.
It used to be that a can of refrigerant was only a $1. How times have changed.

[calvinhc]

I picked up a recharge/sealant kit today. It came with a 4 oz canister of refrigerant with leak sealer and another 8 oz canister of just refrigerant.

After the 4 oz can, it took about a third to a half of the larger can to bring it up to the proper pressure. I found when running, the high pressure was about 1200 kPa and the low was a bit under 400. Let it run for a good half hour to see if anything changed.

So far, so good. I'll be monitoring this over the next couple of weeks and recording the pressure readings.

[Anti_Climax]

If you're logging over time, make sure you get the temp at the same time or you'll have trouble seeing a leak in the comparisons.

[calvinhc]

If you're logging over time, make sure you get the temp at the same time or you'll have trouble seeing a leak in the comparisons.

I figured that would be the case, even though it has been over four decades since high-school chemistry and physics.

For each day, I'm recording: Ambient temperature, High and Low pressure before starting A/C, and High and Low pressure after running A/C for three minutes.

[Anti_Climax]

"CURSE YOU, IDEAL GAS LAW!"

[calvinhc]

The next day, I found the pressures to be about 100 kPa lower, and the ambient temperature was about 10 degrees higher, so it didn't look good.

The second day, the resting pressure was low enough that the compressor wouldn't turn on, so I booked an appointment to have it looked at to find and repair the leak.

I would have used a shop near my home but many don't have the equipment for the 1234YF refrigerant. So, I'm taking it into a dealership.

[calvinhc]

Took it into dealership and after recharging with dye, none is showing up. They have a sniffing unit that isn't detecting refrigerant either.

The technician said one possible leak that can't easily be seen that happens maybe 15% of the time is with the condenser. The easiest way to look for this is on a humid day where condensation of moisture in the air will wash the dye through the drain hole, so this needs to be watched over the next few days.

Hopefully, today's 55% RH will help.