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Discussion Starter #1
Hi All,

Issue: Rising temperature gauge to 75% after 10 Minute drive. No check engine light.

Recently:
  • Battery somehow died, checked battery with CCA around 240 to standard 640 CCA.
  • Installed new battery, starts but rising temperature gauge.
Any suggestions as to what it can be that needs replacement?

Thanks in advance!
 

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Discussion Starter #3 (Edited by Moderator)
Is there coolant in the reservoir?
When is the last time the thermostat was changed?
Reservoir full
Fluid in the radiator full

How do I check if the fans working? I don't know when the fan should turn on to check if it's working.

Since I owned it, it was never changed. I had for about 10 years now.
 

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Change the coolant temperature sender anyway; cheap and easy.

First test for the radiator fans: turn on your AC and interior blower. Fans run?

Also look for obstructions in your grille reducing airflow (leaves, lots of bugs, dead cats, etc.).

Water pump, T-stat also potentially on the list.
 

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1.
This "high speed" fan check is not too hard to do:
Go beneath the radiator. Look for the white electrical connector for the water temperature fan switch beneath the radiator and smaller fan as shown below:

(Viewable by lying on the ground, beneath the smaller radiator fan, looking towards the exhaust pipe.)
Unplug the white connector from the switch, by pressing the connector's tab inboard and tugging. Prying a bit with a screwdriver may be necessary. Now go to the driver's seat with your key and turn the ignition to "On." Leave the engine off. Pop the hood. Are both fans running, and in high speed?

2.
The low speed fan check:
Put the emergency brake on. Start the engine and let it idle in neutral (manual tranny) or park (automatic tranny). At the HVAC control panel on the dashboard, press the A/C button, and turn the blower fan on (any blower speed is fine). The A/C button's indicator lamp should come on. Pop the hood. Are both fans running at low speed?

3.
If the radiator/condenser cooling fan system is working correctly, then either (a) both fans will run (both in hi speed or both in lo speed) or (b) neither fan will run. If only one fan is running during either the high speed fan check or the low speed fan check, report back here.
 

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Discussion Starter #6
Change the coolant temperature sender anyway; cheap and easy.

First test for the radiator fans: turn on your AC and interior blower. Fans run?

Also look for obstructions in your grille reducing airflow (leaves, lots of bugs, dead cats, etc.).

Water pump, T-stat also potentially on the list.
[/QUOfans working.
 

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Discussion Starter #7 (Edited)
1.
This "high speed" fan check is not too hard to do:
Go beneath the radiator. Look for the white electrical connector for the water temperature fan switch beneath the radiator and smaller fan as shown below:

(Viewable by lying on the ground, beneath the smaller radiator fan, looking towards the exhaust pipe.)
Unplug the white connector from the switch, by pressing the connector's tab inboard and tugging. Prying a bit with a screwdriver may be necessary. Now go to the driver's seat with your key and turn the ignition to "On." Leave the engine off. Pop the hood. Are both fans running, and in high speed?

2.
The low speed fan check:
Put the emergency brake on. Start the engine and let it idle in neutral (manual tranny) or park (automatic tranny). At the HVAC control panel on the dashboard, press the A/C button, and turn the blower fan on (any blower speed is fine). The A/C button's indicator lamp should come on. Pop the hood. Are both fans running at low speed?

3.
If the radiator/condenser cooling fan system is working correctly, then either (a) both fans will run (both in hi speed or both in lo speed) or (b) neither fan will run. If only one fan is running during either the high speed fan check or the low speed fan check, report back here.
Thanks Elle

I'll try this coming weekend. Will report back.
 

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Discussion Starter #8
1.
This "high speed" fan check is not too hard to do:
Go beneath the radiator. Look for the white electrical connector for the water temperature fan switch beneath the radiator and smaller fan as shown below:

(Viewable by lying on the ground, beneath the smaller radiator fan, looking towards the exhaust pipe.)
Unplug the white connector from the switch, by pressing the connector's tab inboard and tugging. Prying a bit with a screwdriver may be necessary. Now go to the driver's seat with your key and turn the ignition to "On." Leave the engine off. Pop the hood. Are both fans running, and in high speed?

2.
The low speed fan check:
Put the emergency brake on. Start the engine and let it idle in neutral (manual tranny) or park (automatic tranny). At the HVAC control panel on the dashboard, press the A/C button, and turn the blower fan on (any blower speed is fine). The A/C button's indicator lamp should come on. Pop the hood. Are both fans running at low speed?

3.
If the radiator/condenser cooling fan system is working correctly, then either (a) both fans will run (both in hi speed or both in lo speed) or (b) neither fan will run. If only one fan is running during either the high speed fan check or the low speed fan check, report back here.

Here's my findings:

1) both fans run at high speed. On position.
2) both fan runs, but it sends to be still at high speed. Ignition on and a/c on.
 

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When the fans are in low speed, they are electrically connected in series. When in high speed, they are in parallel. For the moment I am going to assume they are running at the correct speeds for each of the two tests above.

What you unplugged earlier (underneath the Rav4) was the connector for the ECT switch. I would next test this switch. When the coolant temperature rises above about 199 degrees F, the switch is supposed to open, causing the fans to come on. You can check this either by:

1.
Running the engine and raising the temperature of the coolant until you think it is above 199 degrees F. Then stop the engine; remove the key; go beneath the Rav4; and unplug the switch. Use a multimeter to check for continuity across the switch's two terminals. If there is continuity, the switch has failed in the shut position, and the fans will not turn on the way they should. (This approach risks overheating your engine further.)

or

2.
Draining the coolant; removing the switch; and setting the sensor end of the switch in boiling water. Check for continuity. If there is continuity, the switch has failed. This is described at COOLING - 1996 RAV4 | Free Download, page CO-25. There's a drawing to help.

If the switch is fine, then next I would change out the thermostat. Buy either an OEM thermostat or a Kuzeh thermostat, and no other. Kuzeh makes the thermostats for Toyota. I believe the Kuzeh thermostat these days may be bought at Napa and possibly even Autozone. Demoder's thread for replacing the thermostat is excellent: DIY Replace your thermostat & get your cab heat back! . I think this Jonny DIY youtube video is helpful too:
 

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Discussion Starter #10
When the fans are in low speed, they are electrically connected in series. When in high speed, they are in parallel. For the moment I am going to assume they are running at the correct speeds for each of the two tests above.

What you unplugged earlier (underneath the Rav4) was the connector for the ECT switch. I would next test this switch. When the coolant temperature rises above about 199 degrees F, the switch is supposed to open, causing the fans to come on. You can check this either by:

1.
Running the engine and raising the temperature of the coolant until you think it is above 199 degrees F. Then stop the engine; remove the key; go beneath the Rav4; and unplug the switch. Use a multimeter to check for continuity across the switch's two terminals. If there is continuity, the switch has failed in the shut position, and the fans will not turn on the way they should. (This approach risks overheating your engine further.)

or

2.
Draining the coolant; removing the switch; and setting the sensor end of the switch in boiling water. Check for continuity. If there is continuity, the switch has failed. This is described at COOLING - 1996 RAV4 | Free Download, page CO-25. There's a drawing to help.

If the switch is fine, then next I would change out the thermostat. Buy either an OEM thermostat or a Kuzeh thermostat, and no other. Kuzeh makes the thermostats for Toyota. I believe the Kuzeh thermostat these days may be bought at Napa and possibly even Autozone. Demoder's thread for replacing the thermostat is excellent: DIY Replace your thermostat & get your cab heat back! . I think this Jonny DIY youtube video is helpful too:
Thanks! Would a bad ground cause the engine to overheat?
 

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If the fans are running correctly, I do not see how a bad ground would cause overheating. The thermostat is entirely mechanical.

A failed water pump could cause overheating, but I think you would see other symptoms, like problems in the timing belt area.
 

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Discussion Starter #12
If the fans are running correctly, I do not see how a bad ground would cause overheating. The thermostat is entirely mechanical.

A failed water pump could cause overheating, but I think you would see other symptoms, like problems in the timing belt area.
Thanks Elle! I'll replace the coolant temp sender and t stat.
 

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Discussion Starter #13
Still waiting for parts to arrive...

Once the engine is at the normal (at the middle) for around 5 minutes it will slowly creeping up near the red line..

Could it be that the relay fan#2 or #3 isn't turning the fan on?

How can I check to see if and when the fan should running against these relays? I checked the fan when the engine was near the red line, and fan wasn't running.

Thanks!
 

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Here is the electrical diagram for the fans:
The above circuit is from the 1999 manual, but I checked the 1996 manual. I believe the circuits are the same for 1996 to 1999 Rav4s.

The "ECT switch" is called the "A/C water temperature switch" in the diagram above.

With the ignition key in the "On" position and with the engine off, and with the ECT switch disconnected, you found both fans were running, correct? Disconnecting the ECT switch simulates a high coolant temperature. Because both fans were running, this tells me that the relays are fine. Same for the other test (with the dashboard a/c button).

If you want to drive a bit and see if the fans running will keep the coolant temperature low and safe, you could disconnect the ECT switch, leave the fans running, drive a bit as needed, and see if the temperature stays just below the halfway point on the temperature gage on the dashboard instrument cluster.

Do see the 1996's cooling section at Toyota Rav4 1996 Service and Repair Manual + Wiring | Free Download to help confirm the diagnosis here.
 
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