i-Miev Cabin Heater stop heating

[Andreb1160]

I did a couple of rides lately. I changed a few things for these rides. First I cleared the B1108 code and I put some isolation around the liquid reservoir. Then I preheated the car before driving. And while driving I was using the recycle mode of the ventilation most of the time. Using cold air from outside as less as possible. I did drive on a highway but not very long. In short I was doing all I could to help the heater do its job.

Interestingly in these conditions the heater was able to keep up the liquid temperature close to its target and it (or the pump) did never shut down as it was before. This tells me that the problem is not random like a bad connection somewhere. The problem seems to be in the design of the heater fault detection. Either the 3 degrees is too much or the time allowed to heat the liquid is too short.

I wish I could reprogram the computer in my car and tweak the algorithm, I think it would be easy to get rid of these shut down lol.

If it is not the too tight fault detection algorithm then I can imagine one more thing that could cause the problem. A heating resistor in the heater is broken and prevent the heater to heat at its maximum power. It would explain why the heater can't keep up in severe cold conditions and can keep up when we lower the heating requirements by preheating and using recycled air.

To eliminate this faulty resistor possibility I need to know the maximum power of the heater and a way to measure the real time power consumption of the heater to confirm that the heater can or cannot heat at its maximum power.

 

[Andreb1160]

Tonight I did another interesting observation. I parked the car outside (3C) and let it cool down for 2 hours, Then I drove the car for about 10 minutes. Here is the graph:
https://drive.google.com/file/d/1h-O6z2wp6m-ysw1C079VJagLOOb0dsvu/view?usp=drive_link

At the beginning the heater power was 5920W. The liquid temperature was rising but did not reach the target or the 3 deg offset between inlet and outlet within 3 minutes. Then the heater did shut down to 2480W and the pump stopped.

I parked the car but I did not turn it OFF. Then I cleared the B1108 code. The heater power immediately returned to over 5000W and the pump restarted. Clearing the code without cycling the car ON/OFF/ON does restart the heater and the pump which confirm that this code is related to the problem.

 

[MickeyS70]

At the beginning the heater power was 5920W. The liquid temperature was rising but did not reach the target or the 3 deg offset between inlet and outlet within 3 minutes. Then the heater did shut down to 2480W and the pump stopped.

I parked the car but I did not turn it OFF. Then I cleared the B1108 code. The heater power immediately returned to over 5000W and the pump restarted. Clearing the code without cycling the car ON/OFF/ON does restart the heater and the pump which confirm that this code is related to the problem.

Here is a summary of the long thread on the German forum I linked at the beginning

1. B1108 is set after 30s, however the system timer shuts down the heating system about 3 min later
2. Clearing the fault (key on/off) or reducing heating power will reset this emergency shut off timer
3. The car does not measure the actual heating power, the values displayed are just an indication of levels expected (if everything is working correctly)
4. There are 3 heating resistors (different values for each) inside the PTC heater that are turned on via (binary?) signal lines, max power if all of them are active.

Based on the above and symptoms observed our colleague came to the conclusion that one of resistors isn’t active, this could be due to a faulty heater (replacement didn’t fix it though), a broken wire on one of the signal lines (could not be verified as layout appears different to workshop manual) or a faulty control unit (no further information provided). While he didn’t manage to fix it so far, he insulated the heating circuit to preserve what little heat was generated a bit longer.

You are therefore spot on; there isn’t enough heat generated, you could do a quick test to verify: put a clamp amp meter around the PTC heater HV supply and check if the current increases as you turn up the heat…

Mickey

 

[Andreb1160]

Here is a summary of the long thread on the German forum I linked at the beginning

1. B1108 is set after 30s, however the system timer shuts down the heating system about 3 min later
2. Clearing the fault (key on/off) or reducing heating power will reset this emergency shut off timer
3. The car does not measure the actual heating power, the values displayed are just an indication of levels expected (if everything is working correctly)
4. There are 3 heating resistors (different values for each) inside the PTC heater that are turned on via (binary?) signal lines, max power if all of them are active.

You are therefore spot on; there isn’t enough heat generated, you could do a quick test to verify: put a clamp amp meter around the PTC heater HV supply and check if the current increases as you turn up the heat…

Mickey

My observations are a bit different from the German forum:

1) On my car, B1108 do not appear after 30 sec, if I preheat the car, do not drive at high speed for a long time and use recycled air, I can drive for hours, the heater and the pump will keep up and the code will not appear. (I did drive for about an hour with no failure)

2) On my car, Reducing the heating power never restarted the heater and the pump. The only way I found to reset the heater is by cycling the car off/on (key) or by clearing the B1108 code with car scanner.

3) This morning I did confirm that the car does not measure the actual heating power. Putting a clamp amp meter at the input of the PTC heater is a bit difficult for me but I used a different tool to have an idea of the actual current.

I used caniOn to measure the actual total current drawn from the battery while the car is parked. Idle with headlights off and the heater off, my car is using 1.3A. With a battery voltage of 356V this correspond to a consumed power of 534W.

When I turn the heater ON, the battery current start to increase. The heater power indicated in car scanner go up to 5800W BUT the current from battery is never over 7.4A which is a heater power of only (7.4A - idle current of 1,3A = 6.1A * 356V) 2172W!!

This measurement confirm that my heater is not heating at all as it should. Looks like I'm gonna have to change it

André

 

[MickeyS70]

My observations are a bit different from the German forum:

….
….

This measurement confirm that my heater is not heating at all as it should. Looks like I'm gonna have to change it

André

Sorry I should have be more precise:

1) B1108 is only set when the difference between water temperature in/out is >3deg for more than 30s; this then triggers the emergency shutoff timer.

2) The timer can be restarted by various means while it’ is still running (about 3min) but once it has expired the only way to get the heater back online is as you described.
As a workaround one could clear the B1108 DTC when it appears in order to keep the heater going

3) Neat way determining heater power by indirect means, QED..

Our friend got his replacement second hand from Norway for around $400 (1/5 of what the dealer was quoting ) sadly it didn’t fix the problem and he seems to have given up on troubleshooting any further, but there is at least one successful case where a swap did fix the issue.

Good luck
Mickey

 

[KangaRod]

I seem to have this exact problem as well. I live in Winnipeg and it is frustrating in the winter constantly turning the car on and off. The dealer inspected it and said there doesn't seem to be anything wrong, but I don't trust that it was fully tested.

I have a trouble light that came on recently that seems to even prevent me from preheating the car that I'll need to address.

 

[riburada]

Most probably the heater elements are dying.
The heater should consist of three(!) heater elements - 4kW, 2kW and 1kW. The car starts up with 6kw (4+2), as it warms up, just a 4kW stays on. After that 3kw (2+1) and probably will idle at 2kw for some time. If it starts heating and at past some time it blows cool, the probability is that the 1kW heater element has quit working. Quite common on these old cars already. If it has stopped, the 2kW alone wont work, the 1kw shall give out an fault code and for safety allt he heating is switched off. Once restarted, the heating shall continue with 4kW and slowly tries to lower to 2+1 element. And the circle continues.

If you have the remote control for the heater, it only uses 2kW element to heat the water.
My dealership offered to replace the whole heater box for 4,5K€ + labor. Used parts may be handy but thing is - I think everyone has it faulty elements inside. My experience shows that pretty much all of the 10 year old mievs have a faulty heater box.

 

[user 2995]

I replaced mine for £310.
I bought one that looked similar and swapped one cable as it was the wrong type. Had to pay someone to solder it and someone else to reset the airbag which I stupidly unplugged. Easy job though despite the new one being bigger, it fitted perfectly.

 

[riburada]

Yeah probably last for some time. In my mind, the syatem doesn't like 0 current. So... just connect the 1kw line under the 2kw one and it should work just as well.

 

[Rass]

Same here.

I'm installing a diesel-water heater to be nice and toasty.

 

[KangaRod]

I replaced mine for £310.
I bought one that looked similar and swapped one cable as it was the wrong type. Had to pay someone to solder it and someone else to reset the airbag which I stupidly unplugged. Easy job though despite the new one being bigger, it fitted perfectly.

What did you get it out of?

 

[user 2995]

What did you get it out of?

It was on eBay destined for an Azure Dynamics Ford transit connect.

 

[Fisher]

Yeah probably last for some time. In my mind, the syatem doesn't like 0 current. So... just connect the 1kw line under the 2kw one and it should work just as well.

Could You, please, explain what do I have to do to make the heater work better?
I should disconnect 1kW input line and connect it together with 2kW line?
How to identify them?
Thank You for reply

 

[KangaRod]

It was on eBay destined for an Azure Dynamics Ford transit connect.

Oh Jesus lol that doesn’t seem intuitive. Haha

 

[KangaRod]

Since fixing this specific issue seems to be relatively complex; has anyone experimented with using household heaters? I have a small 12v inverter, but it can only produce like 6w or something paltry.

 

[michael8554]

Is there such a thing as a 12V Camping Heater ?

 

[hjdlsnbc]

Yes, there are many 12V heaters out there. Do not heat the air. That is extremely inefficient. Directly heat your body with 12V heating pads and all other things that are directly touching your body. Best placed below your clothing.

Also when your heater in the car is working fine, use those to keep your body warm and not the air around your body.

 

[JoeS]

In the early days of this forum, replacing the i-MiEV's electric heater with readily-available commercial liquid fuel vehicle heaters was relatively-easy and very effective, but not environmentally-friendly. Here are a couple of threads that touch on the subject:
https://myimiev.com/threads/upgrading-the-heating-system-to-bioethanol-or-diesel-fuel.1248/
https://myimiev.com/threads/espar-heater-install.4830/

 

[jray3]

I have good salvaged heaters available for sale, and yes, they're interchangeable with the Transit Connect Electric. I used my first salvaged i-MiEV heater to replace the failed unit an a Transit Connect Electric at least 6 years ago.

Most of the 12V heaters are barely sufficient for windscreen defogging, but the "Back Seat Heat" models have been useful in VW vans for decades. I also experimented with a steel fuel can full of hot water, finding that it was worth more BTU/lb than extra battery capacity! HowEVer, we need a high temperature, high BTU source if trying to make the cabin warm for our relatively short trips. Preheating via the remote control while plugged in (on the defogger setting) is very effective, but a safe plug-in space heater (with PTC elements) can be set up in the interior for use while plugged into the wall.