Dear Rivian Engineers who worked on the Air Conditioning

[LL75]

I've got some experience with sizing of refrigeration systems which is really what we are dealing with here. Systems are designed as, well, a "balanced system". If the problem is that the system is properly designed but undersized for the BTU load (such as underestimating the heat load created by the greenhouse roof in the R1S at 110 degrees ambient), just Increasing the compressor size likely won't fix this type of problem. All of the components - lines sizes (tubing), evaporator and condensor coils, thermal expansion valve or capillary tube, etc. all need to be resized. The only thing a new compressor would fix is if they somehow undersized it in the original design, but since it works fine for many people at or under 100 degrees, I think it's an overall system BTU capacity issue. The other possibility is that it was designed correctly but an OEM is not delivering components to spec.

Thanks for the clear explanation. Guess there are not much rivian can do to improve this

Sponsored

 

[NY_Rob]

My R1S is in for AC service right now. Symptom was ineffective cooling above ~90F outside temperature.

The refrigerant was slightly overcharged (35 grams) and resulted in the compressor shutting down at high ambient temperature due to an overpressure error.

Super sensitive system, 4% or 35 grams = 1.2oz of overcharge causes a shutdown. But I guess it's a relatively small closed system.

 

[Zoidz]

Thanks for the clear explanation. Guess there are not much rivian can do to improve this

Other than making sure that the refrigerant charge (weight) is correct, there's probably not any major improvements they can make. My opinion is that we are seeing a pretty wide range of performance so some are working as designed. The only exception I can think of is that an OEM skimped somewhere on quality and maybe some compressors are not working as well as others. There's a lot of software controlling this, so maybe some tweaks can help, but I doubt any major improvements.

 

[SoCal Rob]

The only exception I can think of is that an OEM skimped somewhere on quality and maybe some compressors are not working as well as others.

There seems to be variability in the compressor hardware just based on the noise levels I’ve heard in some videos. Mine seems to be no louder from outside the vehicle than the electric compressor on my Ford PHEV and quieter than an ICE engine + compressor + cooling fans. It also seems to work well even in the 115° temps shown on the outside temp display. However, I think our outside temp reads high so it was probably more like 105° to 110° outside air temp.

 

[Cactus]

I can assure you that it struggles to make my R1S cabin cool in 120°F outdoor temps in my work parking lot in Phx. My other cars (amazingly) can make the cabin cool. I wonder if I put a white wrap on the sunroof? IMO sunroofs are kind of a useless liability anyway.

This AC problem is almost a deal-killer for me in Phx.

 

[rpmtexas]

I sat in my driveway and tested the AC with an instant read thermometer. At an outside temp of around 103, something in the AC system seems undersized (evaporator coil or compressor) compared to the AC system blower as turning up the fan speed makes the temp of the air coming out of the vents increase by about 7-10 degrees going from level 3-7. I am assuming the compressor is functioning properly although if it isn’t, that could be my problem. At the lower levels, the air was blowing out consistently in the low 50s. At full fan speed the temp went up to 61. It’s a pretty big difference, so I’m thinking that running the fan at full speed may actually cool slower than running it at around 4.

 

[daeHelkcunK]

I can assure you that it struggles to make my R1S cabin cool in 120°F outdoor temps in my work parking lot in Phx. My other cars (amazingly) can make the cabin cool. I wonder if I put a white wrap on the sunroof? IMO sunroofs are kind of a useless liability anyway.

This AC problem is almost a deal-killer for me in Phx.

That's exactly what I was thinking, a white wrap. I wish they would offer a sunroof delete. I'd much rather have an aluminum panel filling that hole, I imagine the weight savings would be substantial and seeing the weight is in the worst place they should consider it. When you live in the south you do everything you can to avoid the sun.

 

[zigzagzap]

In the morning when I pull out of my 95 degree garage, the AC gets reasonably cool/cold after 2-3 mins on my 15 min drive to work. Unfortunately I can’t park in covered parking at work, so the car is very warm in the afternoon. It just can’t cool down on the 15-20 min drive home. Note: I have photo sync plus tinting on all windows (best UV and IR rejection available).

On a 115 degree day earlier this week I drove my model S to and from work. Although the air itself doesnt blow very hard in that car, it’s cold air within a few mins on way home.

So, since the R1S is capable of blowing cool/cold air when the car is not vey warm (95F), I think it is functioning to the best of its capability. However, I think the AC needs to be re-engineered (title of thread) to work better in hot climates like other vehicles do. I would pay for an improved AC retrofit because otherwise, I like the vehicle.

How about using your Rivian app to turn on the AC 15 minutes before you leave to go home?

It would be nice for the app team to give is a scheduled turn on function so the car automatically starts the AC.

 

[Zoidz]

I sat in my driveway and tested the AC with an instant read thermometer. At an outside temp of around 103, something in the AC system seems undersized (evaporator coil or compressor) compared to the AC system blower as turning up the fan speed makes the temp of the air coming out of the vents increase by about 7-10 degrees going from level 3-7. I am assuming the compressor is functioning properly although if it isn’t, that could be my problem. At the lower levels, the air was blowing out consistently in the low 50s. At full fan speed the temp went up to 61. It’s a pretty big difference, so I’m thinking that running the fan at full speed may actually cool slower than running it at around 4.

Was recirc on or off? What was the ambient temperature inside the car?

 

[rpmtexas]

Was recirc on or off? What was the ambient temperature inside the car?

Recirculate was on. Temp in the car was around 78-80 at the time. Also noticing if you leave pet mode on, car gets cold sitting in the sun for 30 minutes but not if I crank the air and drive for 30 minutes. Definitely weird behavior. Not sure why it would cool better set to a warmer temp and sitting still.

 

[Zoidz]

Recirculate was on. Temp in the car was around 78-80 at the time. Also noticing if you leave pet mode on, car gets cold sitting in the sun for 30 minutes but not if I crank the air and drive for 30 minutes. Definitely weird behavior. Not sure why it would cool better set to a warmer temp and sitting still.

Interesting.

One fact we do know is that the cooling system cools the cabin, battery and motors. The rest I'm going to say is strictly my educated guesses. I'm wondering if in these very hot conditions, more cooling is being diverted to the battery and motors when you were driving and therefore less cooling to the cabin. That would explain why pet mode cools well - all cooling is going to the cabin, most likely none to the battery and motors.

Warning - science follows:
Assuming the above, the higher fan speed causing the discharge temperature makes perfect sense. Refrigerant evaporates in the evaporator due to absorbing heat which we see as cool air. Higher air flow moves more heat through the evaporator but if the amount of refrigerant flow is limited, you'll get the same total BTUs of cooling, so the higher volume of air must discharge warmer. You can think of it like a water hose. A gallon is a gallon, and you can fill a 1 gallon bucket in 30 seconds or two minutes, depending on the available flow.

I hope that makes sense. Refrigeration principles are not the easiest to explain.

 

[Scody]

I can assure you that it struggles to make my R1S cabin cool in 120°F outdoor temps in my work parking lot in Phx. My other cars (amazingly) can make the cabin cool. I wonder if I put a white wrap on the sunroof? IMO sunroofs are kind of a useless liability anyway.

This AC problem is almost a deal-killer for me in Phx.

Just put it up for sale, we are on day 6 and returning the vehicle tomorrow. Internal temp is at 79 can not achieve better. Kids can’t deal, and pet mode would be unusable. SC recharged and we noticed a slight improvement. This car is no Match for Florida. Enjoyed it for the most part, but this is a design flaw. The noise this thing makes it’s crazy.

 

[TXR1S]

Until today I thought this was an R1S only problem.

Today I forgot to precool my R1T at 5pm. 103F out. Took a full 20 minutes while driving with AC on full out LO to even be tolerable.

Crazy disappointing.

 

[Cactus]

Interesting.

One fact we do know is that the cooling system cools the cabin, battery and motors. The rest I'm going to say is strictly my educated guesses. I'm wondering if in these very hot conditions, more cooling is being diverted to the battery and motors when you were driving and therefore less cooling to the cabin. That would explain why pet mode cools well - all cooling is going to the cabin, most likely none to the battery and motors.

Yes, for sure the cooling system spends energy to cool the batteries. Here is my post from a related thread.

I did an experiment with my R1S last week.
Background:
Many on this forum have noticed a dramatic drop in efficiency (mi/kwh) when getting in a hot or warm R1S and running the AC while it does its "full throttle weed wacker" impression to make the cabin cool, often unsuccessfully. My R1S goes from a normal 2.2+ mi/kwhr to <1.7 mi/kwh. I have posted this efficiency in another thread.

Methods:
I decided NOT to turn on the AC during my drive home from work (initial cabin temp >125°F) and simply drive ~12 miles with vents blowing and windows cracked about 2 inches WITHOUT the AC on. Then take a picture of the energy graph when arriving home.

Results:
Besides being pretty sweaty by the time I got home, I noticed that the mi/kwh graph does essentially the same thing as when the AC is ON during the same drive home. Efficiency takes a big hit for the first ~5 miles, then gradually gets better.

Discussion:
This leads me to suspect that the vehicle might be trying to cool the battery pack, and that the AC compressor (despite all the racket) doesn't use a lot of power.

 

[Cactus]

How can everyone that is having AC issues write a collective "Dear RJ" letter? I think he truly wants people to love the vehicles they produce. RJ admits when he makes mistakes (raising prices on pre-order holders) and then fixing that mistake (honoring pre-order pricing).

I want to love my R1S. We all do! But nearly everything about the AC system is poorly engineered– from the vent location to the "vent icon drag" to the the collective evidence that it doesn't cool the cabin when parked in the sun and cabin temps are >110°F (I made up that number bc I don't know what it would be).

Google docs?

Sponsored