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The a/c won't turn on at all, or even blow air out the

The a/c won't turn...

The a/c won't turn on at all, or even blow air out the vents, until 45 seconds after I start the truck. After the 45 seconds, it works normally and blows cold air. This started a couple weeks ago.

Mechanic's Assistant: Have you checked the battery, particularly the terminal connections? Are they corroded?

Yes. They are clean. I keep them very clean. Just got back from the parts store, and he checked the battery and it, and the charging system are good, he said.

Mechanic's Assistant: What is the model/year of your Toyota?

07 Tundra 5.7L

Mechanic's Assistant: Are you fixing your Tundra yourself? What have you tried so far?

I always try to fix things myself first. Have googled this problem, and there is no one fix, it seems.

Mechanic's Assistant: Anything else you want the mechanic to know before I connect you?

Someone mentioned the a/c pressure switch may be bad. So, how much will it cost to talk to s mechanic on here? I have used Just Answer before, but it has been a while.

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Answered in 1 day by:
3/13/2018
Peter Bagley
Peter Bagley, Auto Service Technician
Category: Toyota
Satisfied Customers: 1,293
Experience: master tech at Toyota dealer
Verified

Hello and welcome to just answer, my name is ***** ***** master tech of over 40 years experience here to help. I cannot see or hear your vehicle so I rely on your patience and input to my questions so I can help you better.I have read your notes and have a question before we proceed.

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It could very well be the pressure switches which you can check by either jumping the connectors and trying it that way Or I would suggest checking the Freon pressures both at rest and running first that will give me a better picture what is happening.

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Customer reply replied 4 months ago
Okay. Thanks. I've searched the Internet and can't find where the pressure switch is located on my truck. My understanding is there is just one on my truck instead of a high and low one. Can you tell me where the switch is? Also, how do you check the freon pressures. FYI: one the a/c comes on after the 45 second delay it is very cold. One more symptom I forgot to mention, when directing air (heater) to the floor vents, nothing comes out of the floor vents on drivers side but does blow out dash vents.

Here is a picture of the Toyota tech -stream scanner that is needed to do those other tests , I would advise to have this done first before you waist time and money on unnecessary parts as these A/C systems are far more complicated then previous ones. If you still have any questions regarding this let me know. As far as the blowing problem it can be a few things as well. partially plugged vents or a problem with the vent controls, this may be either the control unit itself or a faulty servo. This issue may be related , did both these issues happen together?

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Customer reply replied 4 months ago
Thank you. I'm trying to fix this first myself without having to take it to a shop. Could the freon still be the issue even though the air blows very cold, once it turns on after the 45 second delay? It seems one of the damper doors will not open, since there is no way to get any airflow coming out the floor vents. Just saw your new post: Yes the problem with the delay and the vents not blowing at the floor did happen together. I guess there are little servo motors behind the dash that operate the damper doors. Maybe one of those is bad. The picture of the tech stream scanner did not come through. I think last time I took truck to the shop to have it scanned with tech stream it was $95 just for them to scan it.I bought the pressure sensor at the parts store for around $15, so now that I know the location of that, I will check it, and maybe bridge the contacts in the connector.
Customer reply replied 4 months ago
I'm at work now and cannot switch to a live phone call at this time. Perhaps after work I can try that. Thanks.

ok

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Customer reply replied 4 months ago
Peter, I went out to my truck in the parking lot on my lunch break and located the pressure switch. It is very accessible. So, are you saying to pull the connector off of it, then put a jumper wire between the two contacts on the connector, and see if that solves the problem? Thanks

Just a question, what kind of shop did you have it scanned at? As for the switch put a ohm meter across the terminals and compare . Also if it was a Toyota scanner they can run an active test on that system as well to isolate the problem area.

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Customer reply replied 4 months ago
I have not had it scanned yet at all. You mentioned checking that pressure switch, so was just wanting to know how to check it. It is threaded into an aluminum block piece. I do not want to break the seal on that if it is still good. What kind of reading should I get on the ohm meter. I don't know if it's a normally open or normally closed switch.

all your looking for is continuity no readings as such , you don't have to remove it to do that and if you did you would have to evacuate the Freon from the system first. After you check it for continuity then compare it with the new one. They should read the same, if not most likely the switch. Then you can also jump the plug end to see if that makes any difference in respond time.

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Customer reply replied 4 months ago
Got it. I will try that after work today. Thank you.
Customer reply replied 4 months ago
I went ahead and had it scanned with tech stream and it returned: DTC: B1443: Air outlet damper control servo motor circuit.I found this part, which appears to be the whole assembly with servo motors on it: https://toyotapartsestore.com/2007-toyota-tundra-sr5-gas_4.7_v_8-transmission_automatic_4-hvac-evaporator_heater_components-servo_sub_assy_damp_871060C070-item/Any thoughts? Thanks

Although this has all the servos in it it may be a delay to them or no signal to them and seeing that you have an A/C problem that is also linked to this as you stated acted up the same time . My thoughts are leading to the A/V amplifier which controls all these functions. So before you spend time and money replacing unnecessary parts, lets make sure your getting a signal to those servos first. Would you like a wiring diagram of this system before you attempt any checks?

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sorry typo correction to previous statement should read " A/C AMPLIFIER "

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Customer reply replied 4 months ago
Sure. That would be helpful. I see in the flow chart I found online that it is either the servo, the wiring harness or the a/c amplifier, so I guess I could check to make sure I'm getting a signal to the servos.. Thanks

yup if getting a signal to servos then the part you mentioned would be a good bet but if no signal to it I would bet my bottom dollar it's the amplifier. I can send the wiring diagram right from our manual not some generic online one so you can follow it easily. But this takes time and resources for me to do , so I hope you understand me sending you an extra service for me to send it to you.

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Let me know how you wish to proceed.

Peter Bagley
Peter Bagley, Auto Service Technician
Category: Toyota
Satisfied Customers: 1,293
Experience: master tech at Toyota dealer
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Peter Bagley and 87 other Toyota Specialists are ready to help you
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Customer reply replied 4 months ago
Okay. Sounds good. There are two different plugs I see down there that plug into that servo assembly board, and many wires going into each connector. So hopefully the diagram will be clear on which ones to check, and when to check for the voltage on them. Thanks.

ok be back latter today with the wiring and info

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Customer reply replied 4 months ago
Sounds good. Thank you.

DTC

B1443/43

Air Outlet Damper Control Servo Motor Circuit

DESCRIPTION

The mode damper servo motor sends pulse signals to inform the air conditioning amplifier of the damper position. The air conditioning amplifier activates the motor (normal, reverse) based on the signals to move the air outlet damper to any position, which controls the air outlet switching.

HINT:

Confirm that no mechanical problem is present because this diagnostic trouble code can be output when either a damper link or damper is mechanically locked.

B1443/43

Air outlet damper position sensor value does not change even if air conditioning amplifier operates air outlet servo motor

  • Air outlet servo motor
  • Air conditioning harness
  • Air conditioning amplifier
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INSPECTION PROCEDURE

PROCEDURE;

1.

READ VALUE USING INTELLIGENT TESTER OR TECHSTREAM (AIR OUTLET SERVO MOTOR TARGET PULSE)

(a) Use the Data List to check if the servo motor is functioning properly.

(1) Intelligent tester

HINT:

Since the servo motor cannot be inspected while it is removed from the vehicle, replace the servo motor with a new one and check that the condition returns to normal.

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Now I am down loading a few pages including wiring and pin locations , this will take a while.

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here are the terminal locations and check points

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these are the wiring diagrams , if you put them together you will see the complete picture and area of concern I marked where the servos are.

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more

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last one

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here are the connectors. Just to send along some extra info , you may want to have them hook it up to a smart scanner so they can quickly do an active test on those servos which would tell you right away if it is a servo or the amplifier right away. In my experience dealing with these systems it was usually the amplifier. Also with the smart scanner they can also customize the controls to suit your needs how the servos work. Hope this helps you out , best regards.

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Customer reply replied 4 months ago
Wow! That is a lot to digest, and will take while for me to review and test. Thanks for sending the info.

Let me know how it goes, as I said wasen't easy and you may want to do an active test

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Customer reply replied 4 months ago
Will do. Thanks.
Customer reply replied 4 months ago
A neighbor has access to a techstream scanner, so hopefully that can be used to test the voltage going into the servo from the amplifier just be plugging in to the test port, rather than having to hook up directly to the pins in the connector. I already ordered a new servo assembly board from Toyota. They said I could return it if that ends up not being the problem, as long as I haven't installed it yet. It was just over $100. The amplifier is around $300. Also, I suppose there could be some mechanical blockage behind the dash that is blocking one of the little arms that moves the damper doors. I have cables run all back there from my aftermarket radio and such.

if it is compatible that would be a great help, you can then possibly do that active test on the servos as I mentioned and that would eliminate them.

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Customer reply replied 4 months ago
Yep. I will try to get that done after work today. Thank you.
Customer reply replied 4 months ago
I just did an active test on the air outlet servo pulse. Not sure if I'm doing it right, but it appears the correct voltage is going to the servo, but it must be mechanically stuck, or the servo motor is bad. I'm turning the control from left to right for air flow direction, starting with air from dash onto your face only, and that gives reading of 9, then turn clockwise for air on face and feet, and that reading is 32, then continue clockwise for air only blowing on feet and that reading is 56, then continue clockwise for air on feet and defrost and that reading is 91, then continue clockwise to last position of defrost only and that is 97. That sounds to me like it's getting the correct voltage, but the air flow is not following what I am selecting, so like I said, maybe mechanical blockage, or maybe bad servo motor. What do you think?

Sounds good , but one thing to do also is take your cabin filer out behind the glove box and look carefully in there for any creature nests and such , we have found lots of things in there..

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Customer reply replied 4 months ago
Yep. Just changed the cabin filter. No obstructions in there. So, does what I say sound right? I could not find any specific voltages listed in the documents you sent me. It just says it should be 0 - 255, which all the values fell within that range. And because they changed as I switched positions of the knob, that seemed to me like it was getting the correct voltage, so I should look to the servo motor itself, or for mechanical blockage of the arms. Do you concur? Thanks

according to those notes I would say your on track yes.

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Customer reply replied 4 months ago
Sounds good. Thank you.
Customer reply replied 4 months ago
I haven't had a chance to take the truck apart to get in there to check the servo assembly and install the new one if that's what it needs. I hope to be able to do that in the next few days. I would like to wait to close this out until after I get it done in case anything else comes up. Thank you.

No problem , I will check back on any notes you post. Good luck.

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