Heater problems

Tiny
BACKWOODS BRIAN
  • MEMBER
  • 1999 TOYOTA 4RUNNER
  • 3.4L
  • 6 CYL
  • 4WD
  • AUTOMATIC
  • 105,223 MILES
No heat.
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Monday, January 14th, 2019 AT 10:18 AM

1 Reply

Tiny
JACOBANDNICKOLAS
  • EXPERT
Hi and thanks for using 2CarPros.

No heat can be the result of several things. Most commonly, low coolant is the cause. First, take a look through this link:

https://www.2carpros.com/articles/car-heater-not-working

Now, if the coolant level is full, I need you to allow the vehicle to reach operating temperature with the heater on full. Next, open the hood and locate the two heater core hoses which will attach at the firewall. Both should be hot. If you find one hot and the other cold, we have one of two problems. Either the heater control valve isn't moving to allow hot coolant to enter the heater core, or the heater core is plugged.

Here are the directions for replacing the heater control valve. I'm adding them for two reasons. First, I want you to know what to look for and how it works. Second, I need you to have a helper adjust the heater control from cold to hot while you watch if the valve is moving. If it isn't moving and the cable is good, try to turn it by hand. If you can't, replace it.

________________________

REMOVAL

1. DRAIN ENGINE COOLANT FROM RADIATOR

HINT: It is not necessary to drain out all the coolant.

2. DISCONNECT WATER VALVE CONTROL CABLE FROM WATER VALVE

See picture 1

HINT: Manual A/C only: At the time of installation, please refer to the following item.
After connection, adjust the control cable

See picture 2

3. DISCONNECT WATER HOSES
a. Using pliers, grip the claws of the hose clip and slide the hose clip along the hose.
b. Disconnect the water hose.

See picture 3

HINT: At the time of installation, please refer to the following item.
- Heater radiator pipe:
Push the water hose onto the heater radiator pipe as far as second ridge on the pipe.
- Water valve:
Push the water hose onto the water valve pipe as far as water valve.
- Install the hose clip in a position, as shown in the illustration.

See picture 4

4. REMOVE WATER VALVE
Remove the bolt and water valve.

INSTALLATION
Installation is in the reverse order of removal.

See picture 5

Auto A/C:
AFTER INSTALLATION, ADJUST WATER VALVE CONTROL CABLE
a. Ignition switch ON.
b. Set the temperature control door to "COOL" position and connect the control cable and lock the clamp.

HINT: Lock the clamp during lightly pushing the outer cable in the direction, as shown in the illustration by an arrow.

If the valve is moving and there is no damage to the cable, then suspect the heater core is plugged. Here is a link that shows in general how to replace one:

https://www.2carpros.com/articles/replace-heater-core

___________________________________________

Here are the directions specific to your vehicle for core replacement:

__________________________________________

REMOVAL AND INSTALLATION

See picture 6

COMPONENTS

REMOVAL

1. REMOVE COOLING UNIT
2. DRAIN ENGINE COOLANT FROM RADIATOR

HINT: It is not necessary to drain out all the coolant.

See picture 7

3. DISCONNECT WATER HOSES FROM HEATER RADIATOR PIPES
a. Using pliers, grip the claw of clip and slide the clip along the hose.
b. Disconnect the water hoses.

See picture 8

HINT: At the time of installation, please refer to the following items.
- Push the water hose onto the heater radiator pipe as far as the second ridge on the pipe.
- Install the hose clip in a position, as shown in the illustration.

4. REMOVE INSTRUMENT PANEL AND REINFORCEMENT
5. REMOVE DEFROSTER NOZZLE AND HEATER TO REGISTER DUCT
6. REMOVE HEATER UNIT
a. Auto A/C models:
Disconnect the connector from mode control servomotor.
b. Auto A/C models:
Disconnect the aspirator hose from room temperature sensor.
c. Auto A/C models:
Disconnect the water valve control cable.
d. Remove the 2 nuts and heater unit.

INSTALLATION
Installation is in the reverse order of removal.
___________________________

Let me know if this helps or if you have other questions.

Take care,
Joe
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Monday, January 14th, 2019 AT 6:15 PM

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