[Elle__Rav4]

First check:
-- Remove the key from the ignition.

-- Go beneath the radiator and unplug the temperature switch installed in the bottom of the radiator, near the lower radiator hose. Unplugging the switch simulates a high temperature condition. This is not intuitive, due to the logic circuit the cooling fan electrical system uses.

-- Put the key in the ignition and turn it to "On" (engine not running).

-- Do both fans come on, and in high speed? They should. Report back here.


What year is your Rav4?

 

[Elle__Rav4]

2000 fwd, the fans do come on high when that is disconnected and the switch is new a week ago.

Good. This means the relays are working correctly.

Who is the manufacturer of the new temperature switch?

Please test the old temperature switch and the new temperature switch. For instructions on how to test the switch, go to Elle's 1996-00 Toyota Rav4 Site and download the guide titled "Cooling Problems." In this guide scroll down to the section that gives tests you can do on the temperature switch.

Next, run the engine and feel the top radiator hose and the bottom radiator hose. Is there a large temperature difference? If so, the thermostat may have failed shut. When the thermostat fails shut, the coolant temperature at the temperature switch will tend to stay low.

When was the thermostat last replaced on this Rav? Was a Toyota thermostat used? Was the thermostat installed with the jiggle valve in the correct position?

Fuses do not have polarity.

 

[Elle__Rav4]

Carquest Premium Engine Cooling Fan Switch from Advanced Auto.

I tested the new switch and the old one, the old one was not working. The new one did work prior to install, no logical reason it would stop working but I can test it again installed easily enough tomorrow.

When I make the fans run with the AC on, it cools to normal operational temperature, thus the thermostat is not the problem.

No, this is not enough to conclude that the thermostat is fine. It is entirely possible that the A/C fans running in low speed draw enough cool air across the engine itself to keep the coolant temperature low.

I am not there, boots on the ground, like you are. From what you have posted so far, and at this time, I would not assume the thermostat is all right.

After the engine is warmed up, again I recommend you feel the lower hose and compare how its temperature feels to the temperature of the upper hose and report back. Here is another site with some easy checks to see if the thermostat is stuck shut:

3 Ways to Tell if Your Car's Thermostat Is Stuck Closed - wikiHow

Your vehicle's thermostat opens to allow coolant to flow through the radiator and cool the engine down. However, if the thermostat gets stuck in the closed position, the coolant can't flow through the radiator and can make your engine...

www.wikihow.com

If you study the wiring diagram that avisitor provided, then you will see that unplugging the temperature switch (at the bottom of the radiator) is equivalent to the temperature switch (at the bottom of the radiator) opening. From the wiring diagram and extensive experience with it and our Rav4s, the following are true as a result:

Fan Relay No. 1 coil loses its ground and so loses power. The wiring diagram shows the relay in the de-energized position. The Fan Relay No. 1 switch is SHUT (closed).

Fan Relay No. 2 coil also loses its ground and so power. The wiring diagram shows the relay in the de-energized position. The Fan Relay No. 2 switch is OPEN.

A/C is off, so the Fan Relay No. 3 coil has no power. The Fan Relay No. 3 switch is OPEN.

If one then traces the circuits for the two fan motors, one will see the fans are supposed to run in parallel, meaning high speed.

Since simulating coolant high temperature //at the temperature switch// (by unplugging the switch) does cause the fans to come on, the only explanations I see so far are that either (1) the switch is bad or (2) the switch is not seeing a high enough temperature, due to a stuck shut thermostat or possibly an incorrectly installed thermostat.

 

[Elle__Rav4]

Update, both hoses were hot

Got it. This suggests the thermostat is fine.

but the switch did not open when I checked,

my brand new one!!!
This is especialy frustrating since it passes the hot water test prior to install

so I will be returning it as I suspect it's now broken or opens at the incorrect temperature.
I will be searching for the replacement keeping in mind the toyota made model
I did not look at the temperature ratings for this new one, if that's a factor???

Per the Toyota manual and for your reference, a properly working temperature switch is supposed to open at 199 degrees F (turning the fans On) and then shut at about 181 degrees F (turning the fans Off).

If you post the part number and maker of the aftermarket switch, then I will do some research on it.

As needed, the OEM switch's p/n is 89428-33010.

This is one of several electrical parts for which I would only buy Toyota OEM; Denso; or Aisin.

If you are on a budget, I would not think twice about going to my local UPull-It Salvage yard and buying a used one (with an exchange policy). Several Toyota models from the 1990s use this same temperature switch. Put the p/n in here and you will see the models: www.toyodiy.com/parts/xref

 

[Elle__Rav4]

I have replaced and tested the Switch at the bottom of the radiator with an old switch and new one both giving the exact same results of 2.5 or 6 Ohms when Hot, but closed circuit when cold. That is the correct response even if I can't get it to open and have infinite resistance using hot water. Also there is 12 V at the connector.

Unacceptable test.

I do not understand why you would think this is the correct response.

The first generation Rav4 has either three VSVs or five VSVs (for the manual tranny AWD). I have no idea which VSV you mean.

The fans for the AC run regardless of the coolant temperature, except when the coolant temperature hits 199 degrees F. At 199 degrees F and higher, the fans run in high speed. The AC does not bypass per se the temperature switch, but to understand this, one has to have some electrical background and then study the wiring diagram. The A/C running both fans on low does not confirm the switch is operating correctly.

I am having difficulty following where you are at.

You will get there. But I am not sure I can help you.

 

[Elle__Rav4]

Ok, there is NO Thermostat and the flow tests good when I use other methods (feeling tge hoses, so no clog that I can detect!

I will put a tgermostat in but its not the current issue.

The RDI fan does not come on individualy or in tandum to cool the engine when it gets hot.

Please read the following carefully. Please answer any questions. I am speaking from long experience with this system.

-- In normal operations, either both fans are off; both fans are running in low speed; or both fans are running in high speed.

-- The ECU has no input whatsoever into turning the fans on or off.

-- Please confirm once again: With the A/C off; temperature switch unplugged; the key in "On" (but engine not running); do both fans come on and in high speed?

-- I disagree about the absent thermostat not fouling up diagnosing here. For example, the coolant system might be full of air and need a purge. With no thermostat, and air in the system, the temperature switch's probe might stay too cool to open the switch, but the engine could still overheat.

-- Only buy an OEM thermostat or the correct Kuzeh thermostat. This is important. If you need part numbers, ask. Also the thermostat has a jiggle valve which must be oriented correctly when installing the thermostat. If you do not understand, ask.

Doesnt the switch at the bottom of the radiator have to be working or the AC wouldnt cycle through Hi/Low speeds??

I do not know what you mean by "cycle through" hi/low speeds. To use this forum effectively, I think the user has to be very precise.

 

[Elle__Rav4]

A. When I turn the AC on, both fans come on high speed, then switch to low speed when the compressor is not on, then back to high speed, etc.

Got it. I do not like this. In the wiring diagram, notice that there is an "AC Single Pressure Switch" in series with the coolant temperature switch. If the pressure switch is acting up, this may cause the symptoms you are describing. One can bypass the pressure switch (for ten seconds, say) and see if this cycling you describe goes away.

But first, I advise installing an OEM or Kuzeh thermostat and purging the coolant system of air. Get things back as normal as possible (with the correct new thermostat, with the thermostat jiggle valve "clocked" correctly, and a temperature switch that for now, you think is working). Then report back any changes in the performance of the cooling system.

Would you please post the part number of the thermostat you buy?

Can you give some history on this Rav4? How long have you owned it? Has it always had this problem? Or was it running fine for awhile and then this overheating started?

Did a prior owner leave the engine without a thermostat? I have some guesses why someone would do this.

You are welcome. Good for you for hanging in there. If I post anything that is confusing, feel free to ask for elaboration.

 

[Elle__Rav4]

sweet6b9, got it. It helps to know that this Rav4 was recently acquired, with the condition uncertain, so assume nothing, and be braced for surprises (like the absent thermostat).

 

[Elle__Rav4]

-- I guess I misunderstood about the thermostat. I guess you are saying it was always present, except when you were doing some kind of check.

-- Did you install the thermostat so that the jiggle valve is in the position shown below?

-- Do both your thermostats have a jiggle valve, as shown below?

The jiggle valve is at about the 5 o'clock position in the photo above.

-- Correct, both fans run at the same speed at all times, that speed being either Off, Low speed, or High speed.

-- Did you purge the air from the system? What technique did you use?

-- Since both fans come on in high speed with the coolant temperature switch unplugged; the key in On (engine off); and the A/C off, I continue to maintain that the relays are fine.

-- I have several questions to help narrow this down, but I am finding communications very difficult.

You will figure this out.

 

[Elle__Rav4]

sweet6b9, try this: Unplug the coolant temperature switch. With the switch unplugged, the fans should run anytime the Rav4 engine is running. Take a long test drive. Do not use the air conditioning. Does the engine overheat? (If the engine starts to overheat, pull over and let it cool down.)

 

[Elle__Rav4]

The engine cooling works just fine when the RDI fans work, so no.. not the radiator.

I hear your frustration.

I advise you take whatever coolant temp switches you have at this point and test them all exactly as described here:

When you do the test, please take pictures of your multimeter, showing the ohms readings. Is it possible the multimeter is reading in KOhms or Meg-Ohms, meaning the 4.5 ohms you say you read recently is actually 4500 ohms or 4,500,000 ohms?

What is the make and model number of your multimeter?

Respectfully to IowaGold, I would not trust any aftermarket switch, including Import Direct. Please understand that Import Direct is //not// OEM. Import Direct's advertising is a bit misleading for anyone new to the world of Toyota parts. I would only use a Toyota OEM switch. You pay more. You get more.

 

[Elle__Rav4]

Where should the needle be on the gauge in the dash cluster when the RDI fan comes on to cool the engine?
below the half way mark?
At the half way mark?

At the half way mark or higher.

Normal operating temperature is a hair below the halfway mark.

I admit it is hard to believe all three (or two?) of your switches are bad. Yet the fans are not coming on.

Posting photos of what you do may help enormously.

I am still not confident about your thermostat work. Readers here cannot directly observe what you are doing. Hence the need to try to answer people's questions exactingly. For example: What is the manufacturer's name on the thermostat? Do you understand what it means to install the thermostat's jiggle valve at the correct "clock position"? This is a big deal. If the jiggle valve is not correctly positioned, overheating will happen.

Also you keep referring to the "RDI Fans." The latter is very confusing. Using the names that the service manual uses is best. One fan is the "Radiator (RDI) Fan." The other fan is the "A/C Condenser (CDS) Fan." I know the service manual names are confusing. But the only thing a person needs to know is that either both fans are running in Hi speed; both fans are running in low speed; or both fans are Off. If one fan is running and the other is off, then something is broken.

Maybe just refer to the fans as the passenger side fan and the driver's side fan.

Use short sentences.

 

[Elle__Rav4]

The switch did not open till the thermometer hit 210 degrees in my water pot test. It did finally open to infinite resistance, but the engine overheats first to the red if I let it go...

I do not like this test result. The switch is supposed to be fully open, with no continuity (infinite resistance), at 199 degrees F.

I would buy an OEM switch or pick one up at the salvage yard. Many Toyota models use this same temperature switch.

The jiggle valve is supposed to line up with the protrusion shown in the drawing in Post #31. I cannot say that the 12 o'clock position is correct.

I am going to keep in mind the bubbles; a possible, partly failed water pump; and more.

 

[Elle__Rav4]

But the switch test in a pot of boiling water is the tell all, these switches have to be at 210 to open which is not a huge difference

For what it is worth, I think this is a huge difference. Maybe a Toyota switch will not fix this, but I sure would not want to continue diagnosing until I had a switch installed that opens at 199 degrees F.

Is the radiator cap the correct one, meaning a Toyota OEM cap? Do not rule this out just because of the symptoms you see. Keep it on the list of possibilities.

But first, get a Toyota OEM switch.