A/C malfunction and weird electrical box question.

I'm new here, just got my first Tundra a 2004 Double Cab. We are working on restoring it to a presentable condition and have a problem with the A/C. It will run if I run a jumper wire from under the passenger dash to the + terminal on the battery and cools very well. However, the switch on the dash panel for A/C will not light up at all, nor will it turn on the A/C. Where do I start?

And at the same time, I found that the Electrical box under the hood has had some "special" attention spent on it. It has a "Littlefuse 150" wired in place and I can see where something melted part of the fuse panel and have no idea what I'm looking at beyond that.

Here is a photo. What am I looking at?

 

It looks like someone ripped off part of the fuse/relay box in the engine bay to get at wires because they couldn't (understandably so) get the box off, or weren't willing to take it off the right way.

If it were me, I'd hit a JY and find a replacement box from a like cab type (double cab) and year. Undo the fuckery from the previous owner. Then evaluate where you are.

Because what I'm seeing in that pic is some serious BS.

PS - if you still have the box lid, you can use it as reference to see what the melted square fuse was. I feel like maybe it was the ALT fuse, but that may be the 120A in yellow to the left of it.

 

And when I say it looks like they cut the box, like, in half, notice the broken/trimmed edges:

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Looks like the socket for one of the main fuses was burned/damaged so they cut it out and bypassed with a resettable circuit breaker. I’m with shifty’ - find a donor in a wrecking yard and install new fuse panel

 

Ok, I just looked it up. I think this fusebox is the same as @BubbaW's.

Looks like I was right. The melted square fuse is the 140A "ALT" fuse which is normally a power input line, I believe from the alternator? Or maybe is the line coming from the + side of battery, I always forget.

From some random website, that feeds power to circuits/fuses for the following:

"DEFOG”,
"ABS NO.1”,
"CARGO LP”,
"HEATER”,
"AM1”,
"PWR SEAT”,
"TAIL”,
"STOP”,
"SUN ROOF”,
"PANEL”,
"OBD”,
"FOG”,
"PWR NO.1”,
"PWR NO.2”,
"PWR NO.5”,
"AC INV”,
"PWR NO.3”,
"PWR NO.4”,
"PWR OUTLET”,
"SEAT HTR”
"BATT CHARGE”,
"TOWING BRK”,
"TOWING TAIL”

First thing I would do is replace the under-hood fuse/relay box, and cut any attached wiring that plugs in underneath in case you need a specialized connector. It's your best next-step.

And hopefully in the process you can ultimately learn why the ALT socket melted. I've seen one other member here where that happened - and ultimately whatever was plugged into the underside of the 140A fuse, it started arc'ing out, without managing to blow the fuse.

 

Is that a picture worth a whole bunch of words



I don't feel an ass whooping of previous owner is proper punishment

 

Well the lid is gone, I knew there was a mess there, but everything runs... except the A/C compressor...
The previous owner was a big CB radio operator and I figure he made mods to run his gear.

I located a diagram of the box at
https://fuse-box.info/toyota/toyota-tundra-2004-2006-fuses-and-relay

That box is the Box No2 Diagram.

# 62 is the one that's all melted... Looks like it was bypassed with the "Littlefuse" circuit breaker.
Here's what it says that fuse was for.
62 ALT 140 "DEFOG", "ABS NO.1", "CARGO LP", "HEATER", "AM1", "PWR SEAT", "TAIL", "STOP", "SUN ROOF", "PANEL", "OBD", "FOG", "PWR NO.1", "PWR NO.2", "PWR NO.5", "AC INV", "PWR NO.3", "PWR NO.4", "PWR OUTLET", "SEAT HTR" "BATT CHARGE", "TOWING BRK", and "TOWING TAIL" fuses

I think that means that it fed power to the box inside the cab, right?

# 55 is for the A/C HEATER system, it's a 30A and is blown. I jumped that fuse, I know, not a good idea, but that didn't help the A/C.

I'll try to locate a replacement box, but in the meanwhile, I'm just trying to get the A/C running. It's pretty hot in Mississippi.

 

Here is a better overall photo.

 

The seller ran a jumper wire from under the passenger side dash to the positive terminal on the battery to show me that the A/C worked, but he thought the A/C switch was busted and not turning it all on.
Where under the dash did he run it? The A/C ran fine and if I knew where he had connected the jumper, I could trouble shoot the A/C part of it.

Trust me guys, I'll get a new fuse box. Just trying to stay cool in the meantime.

 

If you trace that fat black/red wire coming off the LittleFuse, where does it go? Alternator?

I'm not wrong...

Your main power feed to the cab starts by coming the box at position #9 of Bubba's diagram. That just so happens to be the post your 175A MEGA fuse is connected to.

From there, power should feed to the other fused circuits in the intact portion of the box.

Where the box doglegs into the covered "Relay & Fuse" part of the box, you should find a wire bundle coming out, and passing thru the firewall. That's what feeds the in-dash fusebox in its entirety.

So basically what dude was doing was jumpering a wire to whatever circuit in that long list I posted above actually handles the A/C controls in the dash.

I suck at reading circuits and EWDs in these trucks, @BubbaW is king there. If anyone has ideas, I'm sure he will.

 

You are correct, it goes to the alternator.

But, my real question to follow all of this, is, where did he connect the jumper under the dash to make the A/C work?

I can't seem to find anything easily accessible to connect to.

 

He probably ran a hot feed into the fuse box, I'm guessing maybe the "HEATER" circuit?

Where was he, exactly, under the dash?

Can you look carefully at the back of the in-dash fusebox to see if there's anything hinky, any wiring exposed at the rear? Anything unplugged?

Are there any add-a-fuse circuits in the front of the in-dash fusebox?

Are there any non-factory looking wires routing toward the center of the dash from the fusebox?

 

He ran the cable under the passenger side of the dash.
It took him about 10 seconds to connect it so I expected it to easy to spot.
But I can't find anything under the dash on that side that looks distantly related.

The in cabin fuse box was opened, but that is not where he connected the jumper that made the A/C work.

Does anyone have a wiring diagram for the A/C for this truck?

 

For future reference, the 2004 EWD(electrical wiring diagram) pdf and other year Tundras can be downloaded from this site in the electrical Forum courtesy of @RainMan_PNW

(1) Ultimate TUNDRA Wiring Diagrams Collection | Toyota Tundra Forum (tundras.com)

All fuse blocks for a 04 DC are under Table of Contents Relay Locations.

That's one your problems, too smallof a fuse, along with any other previous screw ups by previous owner.

As shown in my previous post from my 04 DC and below chart pic from 04 EWD, the A/C Heater fuse is a 50A

The EWD download mentioned above should help ya until I can upload a few other things.




04 DC Air Conditioning pages attached....

 

There's the king, hard at work

Meanwhile, @LoneWolfJCVD, there's a ton of resources linked up in this thread too: https://www.tundras.com/threads/so-you-wanna-buy-just-bought-a-1st-gen-tundra-eh.115928/

​

 

Yeah right, well the king queen F’d up and marked 50A ABS fuse instead of the 50A Heater fuse

I’m gonna start thinking of you as the Pimp of Tundras dot com

You outta add that link to your signature and make it blink

 

I saw that little blunder, but thankfully the heater fuse is right below it, hopefully OP figured it out.

If only <blink> tag was still supported, I miss the 1990s when blink/marquee HTML tags were still a "thing". But noooo, they had to kill them off in HTML 4.0

 

Thanks for the link to the first time buyers guide @shifty`. I have a lot of experience troubleshooting electrical on old tractors growing up on a poor farm. But I’m at a loss for where exactly he plugged that jumper into under the passenger side dash…

I figured that would be the most logical place to start tracing the A/C issue back to its source.

I’m signing off for the evening, I’ll get back on it tomorrow, thanks for the help. I got the wiring diagrams as well @BubbaW.

 

I can't think of anything on the passenger's side that actually controls stuff, other than the blower motor. The ECU is behind the glovebox, also. Maybe fold glovebox open and look behind it?

 

Nothing "poor" about growing up on a farm and with the EWD, the Tundra should be no problem. I'll keep up with how your doing before I upload the items I put together. Good Luck

 

Well, I thought I was done for the night, but I looked back under the dash and could tell where the insulation had been pulled back on the wire to the blower motor.
I attached a photo of the wire, I think that’s the blower motor.
So, why does sending power to this wire power the entire A/C system?
I know that the insulation looks melted, and that’s because when he showed me that it worked, I insisted on test driving it with the cable connected and it was thin wire that overheated…

 

I cannot imagine why that would be the case, and I only tossed that thought out on a whim because the blower motor, the blower resistor, and ECU are about the only things over there. Props for going back out there and looking again.

Looks like the previous owner was a real piece of work. Obviously didn't fix anything properly. Meth is a hell of a drug.

 

Given you have the EWD, feel confident you would see what he was doing but added below just in case. It appears he was dealing with a possible heater relay issue. You can see the sequence below, he's simply bypassing htr relay contacts and applying 12vdc to blue/red wire at blower and 12vdc via 7.5 A A/C fuse to Integration Control terminal 17 marked AC. I added batt in yellow box simulating what you said he did....wire from batt positive to blwr mtr blue/red wire. The below instructions flow thru might help also.

NOTE reminder:....the 30 A fuse you said was in place for heater needs to be 50 A

 

Wow @BubbaW this makes sense. When he told me it was a the switch that was the problem, I interjected that it was probably a relay somewhere. He said that he bypassed the switch and made it work but didn’t want to spend the time to fix the switch.
I will test the heater relay.
Now if it’s not the relay, could be the switch that isn’t closing the relay, right? That will be the blower switch I suppose?

My son that is going to be the primary driver for this Tundra is currently taking intro to Automotive in HS. I got this as a vehicle for him to get some out of classroom training on as well. Gonna be a great chance for some father/son time together too. Replacing the headlight assemblies, tailgate handle, and taillights this weekend when the parts arrive. Then we have a lot of scrubbing to do on the interior. The exhaust manifold has that common leak, we are triaging and taking care of the most essential parts first.

I’ll update when I know more tomorrow. Thanks for the assistance.

 

It's not the blower switch if what you said in below quote from your first post is still true ?

If I were you.....

I would remove the Center Cluster (5 phillips screws)



I would check the operation of the AC switch.



I would check the Htr relay. If you have a VOM(volt ohm meter), pull the heater relay and check pin 1 to 2 of the Htr relay itself for continuity. If OK, Htr relay coil is good.



I would replace 30A fuse you mentioned earlier with the proper 50A fuse that should be there.




I would clean up that fuse/relay box mess underhood the best you can. Be great IF you have a junk yard nearby.

I would remove that wire he ran from blower motor all the way to battery.

In which order of the above is up to you...

The below is possibly over kill but it's what I saved from a few years back when understanding my 04 DC Air Conditioning system when dealing with a mag clutch issue.

 

I checked for continuity, I set my meter to "Tone" and it doesn't beep when I contact those pins, but it does have a consistent reading of 107.8 Ohms. Which is within the recommended resistance of a good relay... I think. At least this video says that is acceptable... https://youtu.be/mkjSFnHSSis If that's wrong, please let me know.

I removed the center cluster. Checked the A/C switch itself, and it doesn't work. No continuity when I press the A/C button. Just want to make sure I'm reading your diagram correctly, here's a photo of what I tested. If this needs replaced, I suppose I just need a new center control cluster?

I'm going to town in a bit to get a 50A fuse and replace some other "wrong size" fuses that I have found.

Looking at the diagram again, I'm wondering if his jumper wire wasn't just bypassing the 30A fuse that was blown because it was supposed to be a 50A.

 

Also inspect the wiring to the blower motor resistor for more dumbfuckery

 

Yeah, mine didn’t tone either but is normal for that type coil wire. I did however read about same ohms…107.5

One other check you can do as far as double checking the AC switch.
Might have to wait till you get proper 50A fuse.

Check that the 7.5A A/C fuse is good, located in same fuse/relay box as Htr relay

Plug cluster connectors back in, put meter on VDC, gently/carefully poke the pos lead of meter into pin 18 where it will hold, put blower knob on low, push AC button in, crank eng and use one of the bolts holding the radio in for your neg. If that switch is good, every time the magnetic clutch kicks in you should have ~13vdc. As you can see from above drawing, pin 18 is the 13vdc going to mag clutch.



Won’t even try to fathom a guess why he put a 30A in there

 

I want to thank you for your help @BubbaW and @shifty`, your guidance made this a lot easier.
I found the problem.

It was the Heater Relay.

I put the proper 50A fuse in there for the heater, fired it all up and nothing worked still. I used the above advice to track the electricity to the relay and then I didn’t have power on the other side.
So, I used my little kit of crimp connectors and some wire to make pigtail connectors to connect the relay without putting it into the fuse block this way I could test each connection in the relay when it was ‘live’. The relay never closed the circuit.
I tested it again for resistance and it fell in the 50-200 ohms resistance like the video above says it should register to be a ‘good relay’.

I removed the Heater relay and replaced it with the relay marked for the ‘Dimmer’. It’s all working.

Funny thing, this is what I thought it was initially. If I had the lid to the fuse box earlier, I would have noticed that the 30A that was blown was supposed to be a 50A. I could have saved this entire song and dance.

Thanks again guys, this is not the last you will hear from me and this Tundra!

 

Please DO stick around! And thanks for updating on the success. @BubbaW knocked it out of the park on this one.