Fans are not turning on when coolant is hot

[Nervous]

A minor (I hope) problem with my wagon 1995 1MZ. Yesterday I was test-driving it in our community and found out that engine temperature is climbing much higher than it should be (looking it temp gauge). I turned on heat to "Hi" and temp went down. I opened the hood and found out that fans are not ON. Both radiator hoses were hot. If I turn A/C on then fans are on, so relay and fans themselves are fine.
I searched through the forum and through the FSM. Unfortunately, I don't have FSM exactly for my year (95-96 1MZ). There is one for 94, but it was with hydraulic fans. And there is one for 1999 but it is still might be different from 95-96.
So, I thought there is a radiator fan switch located on the bottom of the radiator and this is what I need to replace. However, according to Toyota dealer partznet.com and to ToyoDIY there is no such a thing. Here is a reply from the dealer:

According to the vin you provided, the V6 camry has two electronic temperature switches that are both located on the engine and not in the radiator. 8942830130 Switch Temperature Detect 8942841010 Switch Temperature Detect 2 Here is an image of the engine with both sensors higlighted for reference. If you have any further questions, please don't hesitate to ask.

So, now the question: which of these switches are responsible for turning fans on when coolant is hot?

[Nervous]

Here is the image with highlighted switches:

[BamZipPow]

If you have a multimeter...you should be able to test the switches when they're hot. Check the pins on the sensor. The one that's not showing continuity when at temp(hot) should be the defective one.

[Nervous]

Originally Posted by BamZipPow

If you have a multimeter...you should be able to test the switches when they're hot. Check the pins on the sensor. The one that's not showing continuity when at temp(hot) should be the defective one.

Ok, yeah, of course I have one. Am I correct that those switches are basically the same as that radiator fan switch I mentioned in my first post? And why there are two of them - do the control each fan separately?

[Nervous]

Seems to me the two-wire switch I am looking for is located in thermostat housing along with the one-wire"gage" one:


Once I disconnect it fans are on:


I guess, the OEM part no is 8942841010, price at partznet.com is $64.85. Now need to figure out which one is which at rockauto.com and what is the price.

[fenixus]

the single wire switch is actually the temp sender unit for dash gauge.

check rockauto how they name those coolant temperature switch parts, they might have distinguish them by names (coolant temp switch vs coolant temp sender vs coolant temp sensor).

not sure if i'm right, but at least my 5s-fe also has the third switch (sensor actually) for reporting coolant temperature for ECU (E.F.I.)... your setup is all different, my fan switch is located in bottom of radiator below passenger fan.

one thing is sure, you have found the faulty part (fans come on upon disconnecting)

[Nervous]

Hmmm... I was sure the problem is in that switch. So, I removed it from the housing and decided to test in boiling water just in case. Initially, it has continuity. I put it into boiling water (100 C) and - bingo, no continuity! Added some ice into the hot water - bam, continuity is there again....
I am going to install it back and test on vehicle once again. Probably, there was an air tap or something. However, how the temp gauge sensor that is located virtually in the same place registered rising temperature? No answer for now.
And I still don't know the purpose of the second temperature switch that is located at the water inlet. There are two of them there, one is actually a sensor (similar to the gauge one, with one wire) and another one is the switch. But what exactly it does switch?

[fenixus]

so the fan switch tested out in a hot bath ? have you tried testing it a few times in a row to make sure it opens the circuit EVERY time ? this switch may still work intermittently.

how many coolant temp switches you have in there, 3 or 4 ?

dash gauge sender is the one with single wire, so the driver sees dash needle rising above middle if temp gets above normal range 185-215F (this range is pointing to same spot on dash as middle).
third one would be for reporting coolant temps to ECU (so called "ECT for EFI" - so ECU knows if engine is still cold or warm already).

you could try getting one of those tiny gizmos and drive around with it in pocket.
http://www.harborfreight.com/non-con...ter-93983.html

next time you see temp increase on dash gauge, just pull over, pop the hood, wait like 2 minutes to see if fans are engaging, in meantime measure the coolant temp at hoses (compare upper and lower hose temps) with a non-contact thermometer. if thermometer shows like 220-230F then your dash gauge is good and the fan switch is bad.
however if fans do not engage because they see below 220F that means the fan switch is good and something is wrong with dash gauge sender unit.

another option is that you have air in the system as you pointed out. if you have more than 1yr old coolant maybe it's time for a coolant flush (and bleeding/burping) ?

with this pocket thermometer you will be able to tell which one is lying to you.

[Nervous]

Coolant is new (actually, it was mostly distilled water, thanks to 73sport - he recommended to put mostly water (with a bit of coolant) for the first run in the case if there will be a need to drain it again).
Yes, I tried several times to put the switch into hot bath and it worked just fine.
Actually, I am puzzled right now. I can't find the second temp switch, the one with OEM no 89428-30130. Here is the one I suspected (2 wires, located in thermostat housing upward; another one in there, one-wire, located rightward is the gauge's sensor, I didn't remove it):


Now, I tried to find another switch, following the schema in the second post. Here is the place at the radiator cap:


I removed the sensor at the "1" position (2-wires):


It has marking saying it is 89422-35010, which is a temp sender (to ECU?). Doesn't look this is a switch, isn't it?

And another one, at position "2" (one wire):



What is that?

And all of them together:


I am lost..... Rockauto shows the second switch as follows:


But I don't have it (or, don't know there it is). However, I already notices that rockauto is not always accurate in names / categories of their parts.... Actually, this one looks like another one I have in thermostat housing which one, as I think, the temp gauge sensor.... So, I am definitely lost now.

[Nervous]

Actually, it is funny. I think that schema (the same is on toyodiy and the same was on toyotapartsnet) is wrong. If you look at the engine outline then you'll notice it is 3VZ rather than 1MZ (see where the oil cap is located).
And yes, the 89422-35010 is the sensor for E.F.I.... So, at least, I can exclude it from equation.

[Nervous]

I went through the FSM for 94 Camry once again and this time I was comparing the 94 setup with my actual, 95-96 one. 94 used hydraulic fans and starting from 95 they use electric fans. So, I looked at the thermostat housing. Mine has two switches/sensors in it and I was sure that the "rightward" one is for the gauge one. No. 94 setup doesn't have it at all! And the sensor I was asking above as "What is that?" is actually the gauge's one:

Postion 3 here is the exact location I removed it from. And the position 4 is the EFI sensor - also confirmed.
So, here is my thermostat housing:

The upward one exists in 94 setup, but the rightward one doesn't! So, I almost sure this is the second sensor I am looking for. And the dealer's/toyodiy schema is actually total crap.
(so bad, there is no FSM for 95-96 MY camrys....)

[fenixus]

Originally Posted by Nervous

What is that?

this above looks like a typical dash temp sender unit. it only feeds temp to the dash gauge, so driver can observe it. it doesn't interact with the system in any way.

And all of them together:

in my understanding, from left to right:
1) dash gauge sender (single wire)

2) Engine Coolant Temperature sensor for EFI (ECU), mine looks almost identical, you can see it in my FS section if you click the red link in my sig.

3) fan switch - this one is mounted in bottom of radiator in my setup, less accurate location than yours, but does the job.

I am lost..... Rockauto shows the second switch as follows:


But I don't have it (or, don't know there it is). However, I already notices that rockauto is not always accurate in names / categories of their parts.... Actually, this one looks like another one I have in thermostat housing which one, as I think, the temp gauge sensor.... So, I am definitely lost now.

aftermarket parts may look totally different in regards to temperature sensors, knock sensors, oxygen sensors and so on. don't worry about it much. to be sure i would get replacement from online dealer by part number you can read off the original sensor/switch/sender unit.

try confirming upper radiator hose temperature (with cheap $10 non-contact thermometer i linked before) when the dash gauge temp is rising and fans are not turning. this will give you the idea of why and how.

also make sure your harness grounds under hood are clean and healthy. poor grounds may trick many electrical parts. more info you could find in Electrical Wiring Diagrams (EWD) for your car generation.

i'm not familiar with 1mz-fe, maybe someone else having more hands on experience with this engine setup can tell you more (73sport's 95 1mz-fe ?).

[Nervous]

Ok, I found the second switch, like I said it is also in the thermostat housing. It is one-wire switch (that is what confused me from the beginning)::



I also put it into hot bath and measured continuity between the only contact and the body of the switch. It works! So, initially, it has no continuity. After I put it into boiling water - bam, there is continuity. Removed from the hot water - again, no continuity. I even hear how it clicks.

So. I am suspecting either thermostat (but it is new OEM, just installed) or air bubble in that area. Going to assemble everything back, fill with distilled water + a bit of coolant and test again.

[Nervous]

Ok, I put everything back, filled with water, ran the engine with opened rad cap until thermostat is opened. Fans came on several times. Ok. Took it to a drive test. Was going well but after about 5 miles temperature started to rise above the middle of the gauge again. I opened the hood. Fans were off, but I saw another interesting symptom. The rad overflow tank was completely full and extra coolant (well, actually, mostly water for now) was leaking through the top of it! It was like thermostat wasn't opened yet. I waited a bit and at some point level of coolant in the tank started to go down and finally it was almost empty (thermostat opened?). After this fans turned on and temp went down. What was that? Could it be because of radiator cap? (I didn't replaced it yet; it was ordered but they sent me the wrong one)

And I still don't get the purpose of the second temp switch, the one with one wire. What is it for?

[fenixus]

i had similar thing happenening to me. it means you still have lots of air in system.

simply, shut the engine down, wait 5 mins and open the rad cap. is the radiator full up to the cap ? if no, you have to make it full, then close, start engine, turn the heater on and burp the upper rad hose (squeeze it hard a few times) until you feel pressure in hose.

keep the overflow tank full because after some local driving (even if temp no longer rises) there still maybe some air in system and it will get sucked in from overflow tank over night (miner did it, was almost empty next day).