Battery fan gets no power

Ha, fooled you! See attached for how the fan looked before and after cleaning!

-Harry

 

No I meant the inside like wear that plug hangs the inside of that whole area I guess you cleaned it because it looks like it never had a speck of dust in there I don't mean the fan I just meant that where the plug is where the water was coming down and getting on the plug If I showed you that area in my car you can see where the hard water stains are still there. Etc your car looks pretty clean I guess you cleaned it or something.

 

Great work on resolution... I have a similar problem on my 07 prius... ecu won't turn hv battery bower on... but hybrid assistant app runs fan perfectly. App talks to ecu thru odb2 port ...so it is telling the ecu what to do...thus proving all wiring and relays are good and working. It's like the ecu doesn't have any software instructions on how to manage the fan.... any thoughts?
Thanks
Frank

 

Is the battery ecu setting codes for the fan or for high temperatures?

Some people think that Toyota's engineers run the battery "too hot". I don't hear the fan run on my 2006 until it hits speed 3 at around 125°F. That has worked fine for the original battery to go 14 years and 160k. I'm not going to mess with it.

If you want to run the fan all the time, go for it. Might gain some battery life (or not). Will shorten the fan life, so keep on top of that.



Posted via the PriusChat mobile app.

 

The contradiction in your words is that the ECU turns the fan on or off.

Blower Motor by MAX2 posted Mar 12, 2025 at 3:45 PM

But why the ECU decides to turn the fan on is another question.

 

Like other posters I never hear my fan running in North Carolina where it's 100° outside until I've been driving a few minutes and I pull up to a stoplight and I don't have the radio on and I'm paying attention I can hear it running on low and then if I'm really running the pee out of the car on a hot day and I pull up to a stoplight or in my driveway or at Walmart I can hear the fan running on higher speed is it on full blast I have no idea but the car is running all that The only time I can run it is when my bi-directional scanners plugged up and I call it up in the software but I'm not going to be doing that while I'm driving the car I'm going to allow the car to do its thing with the sensors and the wiring and all the crap that they put in the car Just because I don't hear it doesn't mean it doesn't work.? It just means it's not on and been called up I'm not a battery expert I don't know what these things should run at but I would think right around human body temperature wouldn't be too bad 96 to 120° somewhere you know I mean come on. Then you see other people wanting to wrap their battery packing dry ice or something to keep it cold I mean that seems a little excessive doesn't it.

 

What was the temperature of the hybrid battery when you used the hybrid assistant app to override the cooling fan?

I am not sure about the Gen 2, but the ECU on my Gen 3 does not turn on the fan until the hybrid battery is higher than ~77F.

 

Here in sunny Southern California during the day the inside of my car is hotter than that most of the year, unless the AC is running.

 

I have the app set to kick the fan on when hv battery reaches 95f… its does a good job of keep the battery temp under control. Without the app… ecu never turns on fan … I I have gotten hv battery temp too high warning …launched app to get fan to run… and battery temp was at 127f… that when I realized the ecu will not mange the fan… that’s was going on before I every used the hybrid assistant app. I’ve thought of wiring key ON 12v source to run the fan all the time to ensure battery stays cool.

 

Ecu does not turn the fan On nor Off…acts like it’s someone else responsibility. But the hybrid nice person app talks to to and through the ecu… and app is able to manage the fan… so all wiring must be good to the fan. Ecu should be able to manage the fan as the app can …
Thanks for wiring diagram…will come in handy!

Frank

 

I just want the battery to stay in oem specs…
Thanks

 

The fan is controlled only by the ECU, not the phone.

With the phone, you create conditions for the ECU: "Turn on the fan when the temperature reaches such and such a value."

After reaching the temperature you set, the ECU turns on the fan.

If you do not specify conditions for turning on the fan ECU, it follows the conditions set by the battery manufacturers and turns on the fan at a different temperature and load on the battery.

Useful things to understand the work.
https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8Cpdf%E6%A0%BC%E5%BC%8F/repair%20manual/04pruisr/05/20zmw/cip0a85.pdf

 

Batteries don't stay in OEM spec they get depleted and get out of spec because their battery storage devices and they degrade over time they're more time sensitive It seemed like If you don't use them and they just sit there they have a tendency to degrade and what have you so when you put a battery in the service you want to be using it not just parking it in the driveway or the car shed so there's always these things you have to kind of get your needs wants and desires in check when you're going to own a vehicle like a hybrid because it may be an excess for some. Meaning that with the expense of the hybrid systems and cost of maintenance it might actually be more reasonable to own a small economical car like a Yaris or a Corolla and forgo the expense of the hybrids extra systems If you figure in the cost of buying your hybrid operating it keeping it running so on and so forth it might pan out that that might be a smarter option but someone has to think of these things before they buy I guess

 

That's exactly my point... without the phones inputs... the ecu will not turn the fan onand the battery overheat warning is trigger on dash.
During testing... I

I was referring to the batteries staying within the oem temperature operating specs... currently they will rise to 127f and trigger dash warning light. Only the hybrid app can manage the blower fan which does a good job of keeping the batteries 95f-105f... I need to fix the ecu fan management so I don't have to reley on app.

 

Without app running ecu allows batteries to reach 127f and triggers overheat light on dash. Turn app ON showed 127f and fan immediately kicked on to max ...which is easily heard... and temps dropped to sage level of 95f in about 20 minutes...
App fan is set by me to kick ON once batteries reach 95f. I need to fix ecu management so I don't have to rely on app to keep batteries in a safe temp zone... I puzzled because it appears all components to run fan work...except the ecu seems to have no instructions defined with in it...

 

So then you're changing the ECU I guess which is weird so that would be the battery management ECU I guess right there in the battery red or black label yeah I have to take the back off that and have a look in there probably just corroded or something It seems your sensors are working okay because you're able to read them and see the temperature with apps and things that can read the temp sensors and like you say the fan does work with an app when it reaches apparently max temperature so that part is working but nothing in between that's really kind of weird but I guess that would have to have something to do with the HV control ECU. And if it's the one under the battery or in the battery up front near the relays usually that's just corroded in a good cleaning will get that back up to snuff cleaning the receptacles and the plugs

 

Except for the fact it does have programming in it to operate the fan. Now that you can verify the ECU is not commanding the fan on, it is up to you or a mechanic/technician to find out why that is.

To which ECU do you send the commands and which ECU is responsible for monitoring the temperature and commanding the fan on?

Are the HV battery temperature sensors (1, 2, and, 3) showing reasonable outputs?

 

Yes… all 3 temp sensors report within a few degrees of each other…middle probe is always slightly warmer…as expected.
Phone app talks to ecu via odb2 port under dashboard… I don’t want to pay for Toyota diagnostics …when there is so much knowledge available on this forum.

 

Next week I am gonna remove all the body panel near the fan and battery and use the wiring diagram recently provided to me. I wish I had an app that could see what the ecu settings are as related to hv blower operation….

 

What is your statement based on?