AC, blower no go

Correct....HI setting bypasses resistor circuit and completes the blwr mtr circuit to gnd. LO uses all 3 resistors to gnd, M1 uses 2 of the resistors to gnd and M2 uses 1 to gnd.



Checking resistor circuit resistors....

 

Thanks for the link @shifty` I checked out the circuit layout and as you mentioned it was a pain to read. I had checked all of the fuse’s and the relay, except the main fuse because I was told if the main fuse is out then the truck won’t start. This was wrong! I popped that sucker out and lo and behold the a/c fuse link was busted! Pic below. The fuses that aren’t getting power are circled below. The fuse on the fuse block that is blown is number 27. Wondering if one fuse links is blown does it affect the subsequent fuses in the block?

There are two fuse blocks for my truck. One for fuses 25, 26, 27, 31 (black block) and another fuse bock right next to that with 28, 29, 30, 32 (green block) I attached pics of the fuses along with circled pics of the fuses and relay that aren’t getting power.

Here is the link to the website I found for the fuses https://fuse-box.info/toyota/toyota-tundra-2004-2006-fuses-and-relay

@BubbaW I have the 4 door 2006 SR5 4.7l V8. I did check the relay socket with the proper voltage and with the engine both off and on with the fan turned on, the relay definitely isn’t getting power and as you mentioned as a result the resister also isn’t getting power.


@noahrexion I’m unfamiliar with FSM but I will look into it and get back with that info.

I had to order a new fuse block so hopefully that fixes this. Sorry for the long winded response I took a few days off from trying to figure it out.

 

Thanks for that. The other important item not mentioned is your CAB type since AC and DC electrical circuits are somewhat different. If the pic in your profile is your truck, I'll assume you have a DC. If correct, consider adding DC to your profile which can be beneficial when working on any future problems.

That F13 fuseable link definitely feeds numerous circuits which explains all the fuses you have circled.
I also wished I had of not glossed over the below quote you mentioned in your 2nd post and should have asked for an explanation. Sure would have saved you some time knowing now what all was not working.

Do you recall what work was going on about that time and are you sure the 140A fuse link is also not open ?
Zooming in on the pic you posted, 140A looks suspicious.
Hopefully a new F13 fusible will get you fixed.

 

@BubbaW Thanks for the info re. truck specs. I’ll be sure to add DC to my profile. Yup that’s my truck in the pic. I really hope this solves some of the issues. It’s good to hear that the F13 link could feed multiple things. Lesson for the day don’t listen to the guys at the parts store. 140A seems to be in tack.

So long story short, before my blower/ac went out I was having issues with my O2 sensors. I’d replaced both and the code kept (still is) throwing P0057 & or P0138. I went to an auto parts store on a whim hoping they could tell me which fuses/relay go to the o2 sensors. Wish I would have just looked it up myself bc the parts guy said he could check my heater relay with this machine they have. I popped out the relay thinking he was going to test just the relay but after I popped it out he stuck the relay circuit reader into the heater relay circuit with the reader connected to my battery. He said “oh I should read the instructions for this thing” I took the damn relay circuit reader off my truck put the relay back in told him I needed to be somewhere and drove off. I tried to turn on my heater right after that and it wouldn’t blow. Hopefully replacing the fuse will fix the blower issue and hopefully there isn’t any further damage.

 

Which O2 sensors did you use? These trucks are very picky with anything other than OEM/Denso.

 

@rock climber thanks for the info both are Denso maybe I’ll stitch to OEM if all else fails

 

Not only that, but which did you replace? There are 4 on your truck, two for the driver side 4 cylinders ("bank 1"), two for the passenger side 4 cylinders ("bank 2"). On each "bank" you have one upstream (before the catalytic converter) and one downstream (after the cat conv.)

I normally recommend, if you start seeing problems with a sensor, doesn't matter if it's the upstream or the downstream, replace both for that specific bank. You can save yourself a world of grief just spending the few extra bucks.

 

Yeah, sounds like you've been thru the ringer for sure and need to be the one replacing the "parts guy" if you have time in future.

Time will tell once F13 is replaced if any other issues.

As for your O2 sensor issue that's hanging around, if you have never replaced them or don't know their history, I would suggest replacing both banks upstream/downstream sensors with OEM/Denso sensors from either toyota dealer or reputable dealer,....NOT Amacon or fleabay

 

@shifty` thats correct. There are 4. Initially it was bank 2 sensor 2 (passenger side, downstream) replaced that one and then bank 1 sensor 2 (driver side head 1 position, downstream) code came on. Replaced that sensor 30 miles later bank 1 sensor 2 popped up again. Suspecting a faulty sensor I swapped bank 1 sensor 2 with bank 2 sensor 2 and the same code came up (bank 1 sensor 2) so it wasn’t a faulty sensor. That’s when I moved onto the fuses/relays

 

@BubbaW haha for sure. He was kind of a nut. I’ll try replacing the upstream sensors as well if the fuse doesn’t clear the O2 sensor issue. Thanks for the help

 

Keep those old sensors for troubleshooting later

Just an info point, in case you don't post back - if you see any codes about 'cat efficiency low', definitely replace the other sensor on the impacted bank.

Main reason it's recommended to replace upstream and downstream in pairs is, sometimes pairing a brand new, highly accurate sensor up with a well-worn sensor that may be a tad dull, is this: Major point of having a sensor before and after cat is to measure the exhaust before/after so the ECU can compare the values and make sure the cats are actually filtering out as well as they should. Two new sensors? Typically going to give equally accurate results. Two old sensors? Typically going to give equally accurate results. One new and one old? They may be just different enough to give a false delta.

If I'm preaching to the choir and you're already aware, disregard. Not saying you HAVE to do this. Just be aware this is something that can and does happen sometimes.

 

@shifty` awesome that makes perfect sense. I’ll probably do it regardless since I’ve already replaced both of the downstream sensors. Thanks!