HVAC blower motor not coming on...what else can I check??

[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!

 

[BamaDrewski]

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!

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.

 

[TheDurk]

Manual or digital control? Very different systems.

 

[pluton]

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.

Sounds like what most folks call the 'blower resistor'. In my '91 Toyota it was bare wire coils mounted on a plinth---and it burned out about every six years. In my '97 it is a much heavier duty ceramic block style resistor.

 

[VolcanoT4R]

Manual or digital control? Very different systems.

Manual system

 

[TheDurk]

Manual system

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/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.

 

[Pedrojr80]

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

 

[VolcanoT4R]

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/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.

Awesome, thanks! I'll get on that today.

 

[VolcanoT4R]

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

Awesome, I really appreciate that. It should help me narrow down the source of my problem. Thanks!!

 

[VolcanoT4R]

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.

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.

 

[TheDurk]

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.

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/hcamanua/insp.pdf

 

[VolcanoT4R]

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/ewdtmc2/ewdtmpdf/ewdsourc/2002/024runne/systemci/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.

So, appears my issue is on the relay side of the switch. Guess I'll bench test the relay again.

 

[VolcanoT4R]

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/hcamanua/insp.pdf

Tested switch per page AC-97 and all checked out.

Thanks for the explanation regarding testing the relay. Doing that now.

 

[VolcanoT4R]

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.

Not sure I have enough experience to know how to do what you are asking me to do here. The way I was planning on grounding the yellow/red wire was to pull the connector out and connect pin 8 on the connector directly to ground. Not sure how to ground the wire if I have the switch connected and set to HIGH. Would jumping pin #1 and pin #4 simulate the switch being set to high?

If not, can you explain how to ground the yellow/red wire with the switch connected? That has me perplexed. Maybe, go in through the back of the connector?

Sorry for the stupid question.

Thanks again for all of your help!

 

[OffRoadGuy]

Damn.. Its great to see you guys come out helping with all these diagrams. I'm like saving each each one for whenever I need to do some trouble shooting. Thanks!

 

[VolcanoT4R]

[MENTION=10169]TheDurk[/MENTION]

Okay, I chugged a beer and went for it.

I jumped pin#1 with pin#4 of the blower switch connector (should be the same as having the switch set to high)
Turned the truck to "ON" (with push-to-start, no brake, hit button 2x)
Here are results at each pin of the 10A AC fuse terminal

GROUNDED:
Battery side: 0.01V
Firewall side: 11.88V

UNGROUNDED:
Battery side: 0.01V
Firewall side: 0.0V

We have officially entered a realm of knowledge that I know nothing about. I tried to read the Power Source EWD to figure out what it all means, but I'm clueless. Hoping this still points to a bad relay and I can snag one at pick-n-pull tomorrow on my way to work. Relying on someone more knowledgeable than I to tell me what the above means.

Thanks again!

 

[TheDurk]

Not sure I have enough experience to know how to do what you are asking me to do here. The way I was planning on grounding the yellow/red wire was to pull the connector out and connect pin 8 on the connector directly to ground. Not sure how to ground the wire if I have the switch connected and set to HIGH. Would jumping pin #1 and pin #4 simulate the switch being set to high?

If not, can you explain how to ground the yellow/red wire with the switch connected? That has me perplexed. Maybe, go in through the back of the connector?

Sorry for the stupid question.

Thanks again for all of your help!

You're making great progress. Yes, retest that relay is first priority. Yes, I was hoping you could rig a probe to apply ground to the yellow red through the back of the connector and touching the contact. But you can skip that now. If it's not the relay itself, we need to know if the fault is on the coil side or the contact side. So if relay is good, pull the relay and check the relay socket for 12V+ at Pin 1 (full-time) and Pin 5 (key on). Then see if you have ground at Pin 3 with Blower switch on HIGH. That will tell us where we need to go. If those tests are all as they should be, jump Pins 1 and 2 and see if the motor runs on HIGH.

Oh, and change that 10A A/C fuse. It's not our problem, but a blown fuse is the only way you get different readings at both ends. So it's blown, or you didn't make good contact.

 

[VolcanoT4R]

You're making great progress. Yes, retest that relay is first priority. Yes, I was hoping you could rig a probe to apply ground to the yellow red through the back of the connector and touching the contact. But you can skip that now. If it's not the relay itself, we need to know if the fault is on the coil side or the contact side. So if relay is good, pull the relay and check the relay socket for 12V+ at Pin 1 (full-time) and Pin 5 (key on). Then see if you have ground at Pin 3 with Blower switch on HIGH. That will tell us where we need to go. If those tests are all as they should be, jump Pins 1 and 2 and see if the motor runs on HIGH.

Oh, and change that 10A A/C fuse. It's not our problem, but a blown fuse is the only way you get different readings at both ends. So it's blown, or you didn't make good contact.

The 10A AC fuse was pulled for the voltage readings. Again, I may not have done this correctly. What I did was pull the fuse and connected the probe (+) to each side of the fuse contacts inside the engine room fuse box while the negative probe was connected to the ground next to the battery. Made the readings under the conditions stated.

I'll test relay pins (after pulling the relay) and report findings.

Thanks!

 

[VolcanoT4R]

You're making great progress. Yes, retest that relay is first priority. Yes, I was hoping you could rig a probe to apply ground to the yellow red through the back of the connector and touching the contact. But you can skip that now. If it's not the relay itself, we need to know if the fault is on the coil side or the contact side. So if relay is good, pull the relay and check the relay socket for 12V+ at Pin 1 (full-time) and Pin 5 (key on). Then see if you have ground at Pin 3 with Blower switch on HIGH. That will tell us where we need to go. If those tests are all as they should be, jump Pins 1 and 2 and see if the motor runs on HIGH.

Oh, and change that 10A A/C fuse. It's not our problem, but a blown fuse is the only way you get different readings at both ends. So it's blown, or you didn't make good contact.

Relay results (with relay out):

pin 1: 12.02V
pin 5: 11.64V
pin 3: (switch on HI) continuity with ground is good

Re-tested the relay:
Continuity between pins 2 and 4: check
Continuity between pins 3 and 5: check
Continuity between pins 1 and 2 with 12V applied to pins 3 and 5: check

Also, tested 10A AC fuse and seems to be okay.

 

[VolcanoT4R]

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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/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_96-02_Repair&Wiring/techinfo.toyota.com/ileaf/02toyrm/02toypdf/02rmsour/2002/024runne/ac/hcamanua/insp.pdf

Okay, while I had the relay out to check pins 1 and 5 for voltage and 3 for ground (with switch at HIGH) (results in previous post) I decided to check the relay for resistance.

My DMM shows a 1 for it's "no resistance" found and all relay pins show "no resistance" with the exception of pins 2 to pin 4 which registered 0.6ohms resistance.