New title: Weak Heater

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Well-known member
Jan 18, 2018
Fort Collins, Colorado
EDIT: After doing more troubleshooting, I believe that the heater is weak or almost dead. I'm still trying to figure it out. But it doesn't seem to be related to the remote, blower, resistor, pump, or charger

Original post:

I'd love some troubleshooting help with fixing a pre-heating issue that my 2016 i-miev has been experiencing. Here's what I've found so far.

When plugged into a 240v charger, I selected defrost with the remote control. The blower, button lights, etc. all come on properly, and it appears to be working. But there's no heat. It's 16F this morning.

Since I have two identical 2016 i-mievs, I plugged them both in at the same time, and compared them in the same conditions. The other car did exactly what it was supposed to do--lots of hot air defrosted the window. The reservoir (under hood) in the cold car was cold, but the reservoir in the warm car was warm.

I unplugged the car, turned it on, and turned on the defrost manually--which made lots of heat and quickly defrosted the window. The AC also works fine.

I remember hearing that the 2016 has a somewhat different heating system then the 2012 cars, which I only mention in case it helps someone troubleshoot with me. If memory serves, the 2016 has both a heat pump and heating coils. If so, could the car use the coils while plugged in, but the pump when operating on battery? Suggesting, of course, that the coils may have died, or maybe a fuse?
i can't find any information about a heat pump being added to the miev; this did occur over on the Laef, but the FSM up thru 2017 still shows a resistance heater for the miev..?

For some reason the remote defrost command is not going active on one of your cars; it is good that you have 2 cars and can easily compare.

The first thing might be to check and verify all the wiring and connectors involved from the remote antenna to the ECUs involved, EV-ECU, Heater Control Unit in dash, and maybe another unknown ECU related to the remote to convert antenna signals to CAN buss commands?

Unfortunately i've not found or seen anything about the remote in the FSM; it may be there but i don't know where to look.
I don't remember where I heard that 2014+ models had a different heating system. I thought that it was here, but I can't seem to find it. Without evidence to the contrary, I'll have to assume that the heater is the same.

After hunting around the web a little (, I suspect that the cause might be a blower motor resistor. The blower, although it still pushes air, seems wimpier compared to the functional car--whether triggered by the remote or set manually. Based in the description from repairpal, this seems somewhat reasonable. Sort of.

Since the remote does start the fan and lights, I don't understand why the result is different. Seems like the remote system wouldn't have parallel wiring, does it?
Not parallel wiring, but parallel separate origins of the command: one comes from the remote antenna thru some control unit that we don't have any knowledge about, and the other from the heater control unit in the dash.

Both of these send a CAN buss message to the EV-ECU under the rear seat which controls the HV power contactors in the pack. This puts the HV to the Heater, then the [? HCU sends the ON.OFF to the heater.?]

Repairpal didn't even include a failed Heater as a cause--it looks like a scammy advertising site to me. click bait.
Yeah, the repairpal site is a little suspect. But the description of the resistor issue is somewhat similar to the problem that I'm having--and a new resistor is only $35 on ebay, so I'll try it.

But you make a pretty convincing argument that I need to dig into the wiring to check connections. It does make sense that a circuit from the remote to the heater activation system is loose. Any idea where to start? I haven't needed to dig into the wiring before, so I'm somewhat intimidated.
Just dive in, you won't hurt anything and you'll learn a whole lot about your car.

i think the remote antenna is under the dash over by the little window on the passenger side. Probably have to remove the glove box and work your way up to get the dash cover open, it's been a long time since i had the dash off and don't remember all the details. You can remove the knee slicers too while you're down there.
Did some more testing this morning. Interestingly, heat also won't activate when the car is plugged in and the dials are set manually. This would seem to eliminate the possibility of the remote system having a role. Glad that I didn't dive too far down that rabbit hole!

So, the question is now why won't it heat while plugged into the charger?
TobyGadd said:
So, the question is now why won't it heat while plugged into the charger?

I’m afraid that’s by (poor) design, you need a remote if you want to pre-heat while plugged in, mine (and your other car) behaves the same…
MickeyS70 said:
I’m afraid that’s by (poor) design, you need a remote if you want to pre-heat while plugged in, mine (and your other car) behaves the same…
Thanks for that info. I should have compared it to my other car. Agreed that it seems like bad design that the heater won't run while plugged in.
I replaced the blower resister, which didn't help. Worth the $35 to at least rule something out.

I did a little more testing yesterday, and I think that the heater actually works, but is very weak. It turns out that it makes a bit of warmth on remote pre-heat, but not much. I just didn't notice it before because it was so cold outside when I first discovered the problem. But the fluid does warm a bit, which I could feel on a warmer morning. What's odd is that it warms more when the car is unplugged and "ready," although not as much as my other car. I wonder if the remote pre-heat mode doesn't call for as much heat as the manual setting, making it feel like the pre-heating isn't working in colder temperatures.

What's certain is that the pump, blower, and remote are fine.

I've found some documentation that should help me troubleshoot the heater by reading diagnostic codes and using a multimeter.

If anyone else has thoughts, please let me know. Thanks!
If I got you right then the ‘problem’ car seems to have a lower heat output (compared to the ‘good’ one) in pre-heat and dash operated mode, which would point to a heater related issue?

Another detail you mentioned: you plugged in both cars at the same time and get different results, what happens if you switch cables between the cars?

The link below might also give a few pointers:,Defrost%2C%20A%2FC%20Off.
Hi Mickey,

Yes, that's correct. It took me a few steps of troubleshooting to determine that one car simply puts out less heat--regardless of whether it is plugged in or not. It does seem to generate less heat when plugged in compared to when the car is running, but I'm not sure that this is relevant. There doesn't seem to be an issue with the remote, blower, pump. resister, or charger.
Ok, you mentioned that the reservoir felt ‘cold’ in comparison to the other car, again that would point to the heater itself…

It’s tricky to get anywhere near it, a lift or pit would make life a lot easier to follow the trouble shooting steps you linked earlier.
MickeyS70 said:
Ok, you mentioned that the reservoir felt ‘cold’ in comparison to the other car, again that would point to the heater itself…

It’s tricky to get anywhere near it, a lift or pit would make life a lot easier to follow the trouble shooting steps you linked earlier.

It does make a little warmth, but very little compared to the other car. On a cold day, it's hard to tell that it's doing anything, but on a warm day it's detectable. Agreed that the heater doesn't look easy to access. I don't have a pit or a lift, so I'm checking to see if some ramps will give me enough room to work.
byronbradley said:
Remote heater (while plugged in) doesn't seem to do anything. I click on the Heat position, give it 1 hour, and press Send. Nothing changes. Any advice?
The remote's interface is very awkward and unintuitive. From what I understand, there's no way to designate either heating delay or duration--which leads me to believe that you may be confusing the charging delay setting with the remote pre-heating function. For pre-heating or cooling, you can really only select the feature (AC, heat, or defrost), and then send the command to begin immediately.
Thanks, Toby. Indeed, the remote is awkward and non-intuitive, especially via reading the owner's manual. I did find the Heat Mode, which had times attached, but Send didn't send. The manual says adjustments inside the vehicle don't affect the function. So far, nothing goes on.

After a full charge, it went higher than usual, up from a former high of 32 miles to 46 miles! But turning on the heat/defrost when leaving dropped it to the low 20s immediately. Went into Turtle Mode. Then I realized I hadn't released the Parking Brake, so, no wonder. I find if I drive very gently in Eco it works well and lasts. Once it goes into Turtle, it creeps, barely. Embarrassing. However, when going down a hill the Turtle Mode goes off and it drives okay until stressed again. Cold weather may also impede it; I'll find out as the season changes.

Don't know if it's weak cells, Battery Management, or whatever. Don't know if there is a diagnostic tool available. Still learning how to work the car and this forum.

I like the car and hope that someday the battery and related devices can be restored or even upgraded.
Just to verify, you are trying to preheat when the car is charging? Also, so you get any beep tones when trying to activate pre-heat? Are you close to the car, with the antenna on the remote fully extended?

As for going into turtle, that’s likely a different issue, possibly a bad battery. But running the heater on battery will drastically reduce range.
If your remote doesn’t beep when the command to preheat is sent, then you may have a problem with the remote—or you may be using it incorrectly. For the former, make sure you are near the car, and that the remote has a new battery. For the latter, carefully read the manual—the remote has a terrible interface, and you wouldn’t be the first person who had trouble figuring t it out.

That said, here’s the sequence that I use to pre heat:

1. Make sure that the car is plugged into the charger. Preheat won’t work unless it is. Close the doors. No key should be in the ignition.
2. Make sure that the antenna on the remote is extended. Press and hold down the power button on the remote until it turns on and makes a little happy tone.
3. Press the mode button (on the side of the remote) twice until the remote screen reads, “a/c off.”
4. Press the right arrow on the front once until the remote screen says “heat.”
5. Press the power button and release it. Don’t hold it down. The remote should make a tone, and then another one about a second or so later.
6. After a minute or so, open the door and see if the heat is on. Inserting the key, unplugging the charger, etc. will end the preheat process.

I’ve heard that some people sometimes have to repeat these steps a couple of times because the command isn’t received or processed by the car. Mine always works the first time, but it’s worth repeating if you get a failure tone.

Please let me know if this works!