Radiator Cooling Fans Run Constantly

It depends on how the fans are controlled and I don't know which it is:
1) There is a thermal relay in the cooling system somewhere that physically closes and makes the fan run when hot.
2) There is a coolant temperature sensor that is connected to a computer board and the signal it sends does more than one thing......like enriching the mixture on cold start and turning on the fans when hot.

I suspect the system works like #2. If that is the case, either the sensor is bad, a wire is loose (or pinched) or the computer board is bad.
In addition to making the fans run, it might be hurting your gas mileage too.

 

Prius has two fans are they bought running? Even if you turn AC off?

If bought fans are operating it can only be problem with wiring, AC-control, water temp switch, or fan relay 3.
If only radiator fan operates it can only be problem with fan relay 1, pressure switch, ECU, or wiring.

It’s easy to continue the fault finding from here but please tell us what fans are running.

 

I can’t tell from the video if only fan on that side is running or are they bought running? Do the fan(s) stop if you turn the AC off?

 

First pull fan no. 3 relay and make sure that fans don’t run when it’s disconnected. Then you can measure resistance between two bigger terminals of the relay. If it has continuity relay is bad and you just need new one. If not you need to find the temp switch and test if removing its connector will stop the fans. If it did then you need new temp switch.

It’s unlikely that those will fix the fault but while doing that you may find the spot that wiring is pinched or something. And at lest you know it’s not simple fix like that.

 

If you require it I have the circuit diagrams for the control of the fans. As an added item please check the fans are blowing into the engine compartment from the front. The fans counter rotate and must be fitted to there corresponding electric motor. These often get swapped with front end damage causing them to blow towards the front.
The fan motors have a two speed operation "connected in series for slow, and parallel for fast".

John (Britprius)

 

All 3 relays are in the fuse box under the hood where the jump point is.

John (Britprius)

 

Driver side fuse box (for left hand drive) its marked FAN NO. 3

 

The strong likely hood is that the wiring has been put together wrongly or has been re wired because the re builder could not get the fans to run. Removing the connector to the engine temperature sensor should turn the fans off if the sensor is at fault "which I doubt".

John (Britprius)

 

Dejavu.

Some of you may recall this poor guy in Nigeria. Fautly Radiator fan connection, P0420 P0A80 P3020 & HV battery | PriusChat

Hopefully OP can repair this.

 

Get the electrical wiring diagram at techinfo.toyota.com so that you can see how the engine cooling system is supposed to work. Then maybe you can figure out where the problem is with your car, which probably is associated with improper repair of the collision damage.

 

You may want to test the r134 pressure switch. There is a simple test somewhere in the forum where you can use a short wire to test the switch.

If you pm me your email address, I can send the wiring diagram to you.

Considering the front end collision, the absence of a code from the vehicle does not necessarily mean the absence of a fault, it only means that the car is not registering the fault codes and this is likely based on the way the car was fixed.

I had a similar issue with a rav 4 which had a front end collision and afterwards didn't register any codes.

 

Hmm, you both have an improperly wired fan. You missed "radiator fan had been directly connected such that it starts with the car on ready (ig on)." Yes, the poor lad from Nigeria is suffering from other issues as well. But both of you have the same underlying wiring issue.

Looking at the wiring diagram for both fans (Condensor & Radiator), its possible the "rebuilders" bypassed the junction connector for each fan motor, which explains Ready = fans on. Diagram attached as a courtesy.

You saved some money on buying a salvaged. Don't cheap out on $15 and the ability to get the Official Toyota Service/Repair manual. It is insanely comprehensive, and the best automotive $15 you will have spent. Link for info on Toyota Service Manual, and printing solutions contained here: Where to get Prius v Parts and Service Manuals? | PriusChat

If you don't own mini VCI cable, get one; $25 at Amazon/eBay. This will give you the same diagnostic capability as dealers, as they use the same cable (granted a genuine cable vs knock off imitation) and software (legitimate vs a hacked copy). This being said, many here have been using the hacked stuff off Amazon/eBay w/o any problems, doing maintenance and reading codes! You can now read the codes w/ accuracy (generic readers miss a lot of codes and give false codes).

Click this LINK, and choose any mini VCI cable; I'd get the cheapest one (new or used). You can always find a newer software version of Techstream somewhere on the Internet.

READ ME FIRST link. The Tundra boys provide an easy ABC, 123, for mini VCI. You should have no further questions after reading this. There is even a link w/in this article for a 64bit Window's set-up.

Hardware Requirements link, by Toyota, just note the speed and RAM requirement for your soon to be Techstream laptop.

To be data safe, assume the hacked Techstream software has malware. This laptop should be a spare "junker," used only for Toyota diagnosis/maintenance; NO email, NO online banking, NO nothing where a user ID and password is ever entered.
Some people have reported success using a Mac laptop in some Windows XP emulation mode.