Originally Posted by VolcanoT4R

2001 T4R SR5
229K
No recent mods or maintenance that may have affected performance

The other day I noticed my HVAC fan wasn't working. Here is what I have checked...

Heater fuse (50A) checked...has continuity-->works
Heater relay checked...works
blower motor connected directly to battery...works
HVAC control swapped with two different controls (working last I checked)...inconclusive
Heater blower resistor (HBR) checked per fsm...results below ("o" is ohms)
Connection | per FSM | Original HBR | Pick-n-pull HBR
1-4 | 2.2+/-0.1o | 3.7o | 3.5o
1-3 | 1.2+/-0.2o | 2.8o | 2.4o
1-2 | 1.8+/-0.2o | 3.4o | 2.9o

Looks like my pick-n-pull HBR might also be a dud, so I'll be ordering one. Should I go OEM or is aftermarket okay here?

What else can I check? Aside from troubleshooting the wire harness (which didn't appear to be corroded or anything), the FSM doesn't

Should I try to put a resistor on the HBR connector to simulate the HBR and see if I can get the fan to come on?

Thanks in advance!

Originally Posted by BamaDrewski

I am pretty sure there is a blower control module mounted to the evaporator core behind the glove compartment. You have to pull the core case out, open it up (clean it while you are in there) and check the motor control. (it looks like a big white chunk of white ceramic). When I did my total AC job, I found the unit/controller was cracked in several pieces. This might help. Just a suggestion.

Originally Posted by TheDurk

Manual or digital control? Very different systems.

Originally Posted by VolcanoT4R

Manual system

Originally Posted by TheDurk

First, it's not your HBR if fan won't run on HIGH. That completely bypasses the HBR.

Sounds like it's the control switch, if you have ruled out the relay.

The switch has to do two things:

Energize the relay coil, and,

Send 12V+ to the HBR (LO or MED) or directly to the motor (HIGH).

Test protocol for the control switch is under Service Hints in the EWD linked below:

http://tacoma.site40.net/4Runner_96-...i/057acman.pdf.

Did you test the relay in place by grounding the yellow/red wire at the blower switch? Did you check if the white/black wire at Pin 1 of the blower switch is a good ground? Try connecting the motor to the battery with switch on HIGH but do just ground and then just battery positive. That will determine if problem is on relay side or switch side.

Originally Posted by Pedrojr80

Here is the wiring diagrm so maybe it can help you pin point the problem

Originally Posted by TheDurk

First, it's not your HBR if fan won't run on HIGH. That completely bypasses the HBR.

Sounds like it's the control switch, if you have ruled out the relay.

The switch has to do two things:

Energize the relay coil, and,

Send 12V+ to the HBR (LO or MED) or directly to the motor (HIGH).

Did you test the relay in place by grounding the yellow/red wire at the blower switch? Did you check if the white/black wire at Pin 1 of the blower switch is a good ground? Try connecting the motor to the battery with switch on HIGH but do just ground and then just battery positive. That will determine if problem is on relay side or switch side.

Originally Posted by VolcanoT4R

I tested the relay by pulling it out and energizing the pins (can't remember which one's at the moment) to make sure I heard it "click". Will test using your method and post results. Thanks again.

Originally Posted by TheDurk

First, it's not your HBR if fan won't run on HIGH. That completely bypasses the HBR.

Sounds like it's the control switch, if you have ruled out the relay.

The switch has to do two things:

Energize the relay coil, and,

Send 12V+ to the HBR (LO or MED) or directly to the motor (HIGH).

Test protocol for the control switch is under Service Hints in the EWD linked below:

http://tacoma.site40.net/4Runner_96-...i/057acman.pdf.

Did you test the relay in place by grounding the yellow/red wire at the blower switch?

Confused by what exactly you're asking me to do here. I understand grounding the yellow/red wire from the connector (with the controller removed), but not sure what I am checking. Should I just be listening to the heater relay to find out whether or not it is coming on?

Did you check if the white/black wire at Pin 1 of the blower switch is a good ground?

Ground at pin 1 of the Blower SW connector is good (checked continuity from pin 1 to ground)

Try connecting the motor to the battery with switch on HIGH but do just ground and then just battery positive. That will determine if problem is on relay side or switch side.

If I understand this correctly, you want me to:

a) "just do ground" essentially bypassing the AC control while letting the truck control POSITIVE voltage. Is this correct? If so, what I did was turn truck on, turn AC control to HIGH, connect connector B6 (blue-red, pin #2) to the POSITIVE terminal on the blower motor and connect the NEGATIVE terminal on the blower motor directly to the NEGATIVE terminal of the battery. Results, fan did not come on.

b) "just battery positive" essentially bypassing the heater relay while letting the AC control (set to HIGH) connect to ground. Is this correct? If so, what I did was turn the AC control to high, connect the NEGATIVE side of the blower motor connector (B6, pin #1: blue/black) to the NEGATIVE on the blower motor and connected the POSITIVE terminal of the blower motor directly to the POSITIVE side of the battery. Results, fan DID come on.

Originally Posted by TheDurk

Yeah, my way will test the relay, as well as the socket, the power supply, and the wiring up to relay contact point. Also, a 'çlick' is by no means a sure good indicator. It can click without passing current. You need to see zero resistance on the contacts with a meter when you test off the truck.



See the way Toyota says to do it:

http://tacoma.site40.net/4Runner_96-...c/hmr/insp.pdf

What I would really like is for you to ground that yellow/red wire with key on and switch on HIGH. Then check for 12V+ at both ends of the A/C fuse. Then do the same without grounding the yellow/red wire. That will tell us a lot. Do that before you test the switch. You may not have to.

There is a better switch test protocol at Item 9 here:

http://tacoma.site40.net/4Runner_96-...manua/insp.pdf

Originally Posted by TheDurk

What I would really like is for you to ground that yellow/red wire with key on and switch on HIGH. Then check for 12V+ at both ends of the A/C fuse. Then do the same without grounding the yellow/red wire. That will tell us a lot. Do that before you test the switch. You may not have to.