Blows fuse when turning on A/C

Tiny
WILLIAM RANKEL
  • MEMBER
  • 2001 TOYOTA RAV4
  • 2.0L
  • 4 CYL
  • 2WD
  • AUTOMATIC
  • 348,000 MILES
Anytime I press the A/C switch it blows the 10 amp gauge fuse which protects that circuit along with several other circuits. As long as I do not engage the A/C switch the fuse does not blow.

Initially thought it was the compressor clutch drawing too many amps. Replaced the clutch but the fuse still blows. Then decided to replace the compressor with another used but working compressor and the same result. Replace it with a third compressor thinking the second one was bad as well and the same result occurred as well. Fuse blows every time the A/C switch is pressed.

What am I missing here? Is it the compressor still bad (doubtful at this point)? Is it the A/C switch itself? Is there an A/C cooling fan relay causing this? Or is it the A/C amplifier. I do not think the cooling fan relay for the condenser is on the same circuit as the 10 amp gauge and compressor are though but I could be wrong.

any help would be great. This has been plaguing me for months without a solution. Again the fuse only blows if I press the A/C switch. Does not blow otherwise. Has to be related to something in the HVAC.
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Thursday, May 18th, 2017 AT 12:49 PM

22 Replies

Tiny
SATURNTECH9
  • EXPERT
Have you tried removing the fuse and hooking a a bulb test light across where the fuse goes?Then the test light should glow bright if there is a dead short on the circuit. You can unplug the compressor move wires around and watch the light on the test light. It will help you find the blown fuse.
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Thursday, May 18th, 2017 AT 6:36 PM
Tiny
CARADIODOC
  • EXPERT
If you suspect the compressor clutch, just unplug it. You do not have to replace it as a test.

A simple trick to finding a short is to replace the blown fuse with a pair of spade terminals, then use small jumper wires to connect them to a twelve volt light bulb. A brake light bulb works well. When the circuit is live and the short is present, the bulb will be full brightness and hot so be sure it's not laying on the carpet or against a plastic door panel. Now you can unplug electrical connectors and move things around to see what makes the short go away. When it does, the bulb will get dim or go out.

The 10-amp "gauge" fuse feeds a computer module in the passenger junction box behind the right side of the dash. Unfortunately the way the wiring diagrams are drawn, there is no way to follow the current path for the AC switch or the module. There is also an "AC amplifier module" behind the center of the dash that you might consider.

The problem is if you unplug a module, then the test light is dim or the fuse does not blow, is it because that module is shorted or because something further down the line is shorted, and current cannot get to that short because it has to go through the module you unplugged? I never approve of throwing random parts at a problem in hopes one will solve it, but in this case, I cannot tell you a logical set of steps to take to find the cause, and this might be one time you will have to just pop in replacements to try. I would find some used modules at a salvage yard, assuming you have not found a bare wire or other cause up to this point.
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Thursday, May 18th, 2017 AT 6:48 PM
Tiny
WILLIAM RANKEL
  • MEMBER
I read the wiring diagrams myself and could not follow or understand the 10 amp gauge fuse. So much seems plugged into or runs through that one fuse that is almost impossible to figure out where the short is. Why would Toyota put that much stuff on one 10 app fuse? Seems like half fee vehicle is on that fuse. Power windows, speed gauge's, shift indicator, charging, AC etc is all on that one fuse. That being said, it has to be something related to the AC. Unfortunately replacing the switch or the AC amplifier are not cheap options. The AC switch is a soldiered board component requiring total replacement of the AC climate control dashboard module. What about condenser fans? What on the vehicle besides the relays controls the turning on and off of those fans? I have not looked at those but if whatever controls the front fans is in the same fuse, it could be that as well?
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Friday, May 19th, 2017 AT 12:43 AM
Tiny
SATURNTECH9
  • EXPERT
If you tried what myself and cardiodoc suggested with the light that will really help. It has to be something with the A/C compressor turning on. Wires clutch etc blowing fuses is not easy to diagnosis. Power probe brand tools makes a circuit tracker that will tell you where a dead short is with a circuit tracer you follow the wires with.
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Friday, May 19th, 2017 AT 6:54 AM
Tiny
CARADIODOC
  • EXPERT
Also, you're forgetting the easiest step. Just unplug stuff.

We're looking at different fuses. On my diagram, it only feeds a couple of circuits.
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Friday, May 19th, 2017 AT 9:04 PM
Tiny
WILLIAM RANKEL
  • MEMBER
So its NOT the AC compressor. I disconnected it completely from the vehicle. Pressing the A/C button now still immediately blows the 10 Gage fuse. I am highly suspicious that the A/C dash module which contains the A/C button, Emergency lights, heater etc all AC controls may need to be replaced. The LED illumination has been flickering on that board for over year. The only other thing I could think of is the AC modulator. That potentially could be bad although its so insanely beyond rare for that to fail that I'm not hedging my bet on it. I don't know a single person that has ever had to replace one of those.

Tried the spade terminals and bulb but even though the bulb stays light when the A/C button is pressed with the compressor clutch unplugged electrically. I still can't really narrow down the fault. This looks like it will be trial an error with parts. I guess I'll try to the dashboard AC control panel first and replace that. Is there anything else I could be missing that I could test? The condenser / radiator fans don't appear to be on the same fuse from reading the diagrams. Hmm.
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Saturday, May 20th, 2017 AT 7:45 PM
Tiny
CARADIODOC
  • EXPERT
Don't replace parts. Unplug them. If a module is shorted internally, unplugging it removes the short from the circuit. Even then there could be something shorted that is fed THROUGH the module you unplugged, so there's more things to check before you order a part.
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Saturday, May 20th, 2017 AT 8:11 PM
Tiny
WILLIAM RANKEL
  • MEMBER
So I happen to own another 2003 RAV4 which runs fine. My 2001 Rav4 is the one that keeps blowing fuses. I took the AC modulator out of the 2003 and tested it in the 2001 with the same result occurs being that the fuse blows. This is a very troubling issue because the vehicle blows the fuse even with the AC compressor unplugged and this fault is nearly impossible to trace.

If I unplug the AC modulator the fuse does not blow but the AC light also does not illuminate. But it's not the AC modulator because like I stated before I tested it with a spare working on that is the same part no from the other RAV4.

I can't believe how many people have the same problem as me on the internet yet no one can solve the issue or find a solution. It's crazy lol. I've spendantany hours on this with absolutely no success.
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Sunday, May 21st, 2017 AT 3:35 PM
Tiny
WILLIAM RANKEL
  • MEMBER
I could try replacing the AC control panel on the dashboard next but I am not sure it would be the actual AC button itself.
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Sunday, May 21st, 2017 AT 3:37 PM
Tiny
CARADIODOC
  • EXPERT
Actually, you made a huge leap of progress, but the way the diagram is drawn, it shows representations of assemblies but not the wires that I can follow. I have found some suspects though.

The best one is a diode block that is supposed to dampen voltage spikes. Diodes are one-way valves for electrical current flow, but diodes often fail by shorting. Look for this assembly behind the right side of the dash, possibly near the fan motor. It has three wires; a black, a light green / black, and a red / yellow or a white wire. Unplug that, then see if the short is still there.

By "AC modulator", could you mean the "AC accumulator"? It's not possible to figure out which circuit feeds that and could have the short on it, but if you unplug the amplifier and the short is gone, we're past the point of confusion anyway. The compressor clutch is one line, but you unplugged that already and it didn't help. Next, another circuit feeds the "Air inlet control servo motor", behind the right side of the dash. That is probably mounted on the heater box assembly. If you can figure out where that is, unplug it. Its wires are, ... Uhm, ... White, white, and white. All three of those wires come right from the AC control switch. If you have another control switch, try that too. It has a number of circuits that get 12 volts fed to them when it's turned on.

Before I get dizzy trying to follow the other wires, check the items I listed so far and see if any of them remove the short when you unplug them.
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Monday, May 22nd, 2017 AT 10:21 PM
Tiny
SATURNTECH9
  • EXPERT
Another suggestion you unplugged the a.C. Compressor and the short was still there I had a car like that. Turned out the wire going to a.C. Compressor in the engine compartment was shorted to ground.
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Monday, May 22nd, 2017 AT 10:41 PM
Tiny
WILLIAM RANKEL
  • MEMBER
Yes I apologize. It was the AC Amplifier Module that I unplugged. Not sure why I typed modulator lol. I was not thinking straight. Obviously we can rule out the amplifier. I could check the air inlet servo but I don't believe that is powered through the AC switch as I can operate the servo without the need to turn on the AC switch. I hear the servo all the time working BUT the servo switch is directly adjacent to the AC switch. I'll find it and unplug it tomorrow just to rule that out. Also. What about the possibility that it is the actual AC switch itself? That AC switch and climate panel is not at all easy to remove on a rav4. Otherwise I would swap the one from 2003 into the 2001 to rule out the AC panel. (I may have to do this anyways :-( though)

Also whenever the 2001 Rav4 blows the fuse, it almost sounds like I can hear a pop behind the gage cluster but the fuse box is located underneath the dashboard on the lower left by the door. Could just be my hearing though and I'm actually just hearing the fuse itself pop.

It is also possible that the compressor wire in the engine could be shorted to ground somewhere. Unfortunately, it would require me to complete dismantle the wiring harness to inspect the wire itself. Something I'm afraid of doing because it seems fairly fragile. This vehicle does have 348k. Original engine and trans. The wires are ok but the outside protective sheaths of the bundles are not in good condition.
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Monday, May 22nd, 2017 AT 11:04 PM
Tiny
CARADIODOC
  • EXPERT
Saturntech9's comment reminded me that some vehicles use a spike-suppression diode in the wiring harness near the compressor clutch's plug. If that diode was shorted, that short would be on that line but unplugging the compressor wouldn't change anything.

I don't know how this system works, so I don't know which other wires get 12 volts from the "Gauges" fuse. I'm starting from the amplifier instead, but it could be the amplifier itself is shorted. It has a ground wire, a 12 volt feed wire, and some circuitry in between. That means it's a candidate for creating a short between the feed and ground wires.

What I'm thinking this might come down to is checking each amplifier wire individually to see if we can find one with a short, but that's easier to do than to describe.

I'll be back tomorrow to read that you solved the problem!
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Tuesday, May 23rd, 2017 AT 12:20 AM
Tiny
WILLIAM RANKEL
  • MEMBER
The wires from the amplifier and other harnesses that plug into the ac control panel do not appear to be shorted or chaffed in anyway. Granted. I can only see what is visible until the wires descend into the bundled wraps which I'm not undoing. There must be a short somewhere. The harness to the compressor appears in good shape. One small chaffed area in the outer sheath but upon close inspection there is no cracked wiring or missing insulation on the wiring itself that would cause a short to ground UNLESS it is hidden within the bundle which I highly doubt would be the case. I still need to inspect the wiring further down the line closer towards the end of the unplugged compressor wire.

FYI, a little more info I discovered today. When I turn the keys to power the vehicle but not start it, the AC button will illuminate and not blow the fuse if I press it in. The fuse only blows when the engine is running and the AC button is engaged.
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Wednesday, May 24th, 2017 AT 11:16 AM
Tiny
CARADIODOC
  • EXPERT
Unplug the AC amplifier, then find terminal # 6 in the plug. That's listed as a "black (or white) wire. Measure the resistance of that wire to ground. Tell me what you find.

Do that test again with the AC compressor unplugged and tell me what you find.
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Wednesday, May 24th, 2017 AT 11:46 AM
Tiny
WILLIAM RANKEL
  • MEMBER
No luck. I wasn't able to really test the resistance. Could not get contact with the terminal. I still think it is something with the AC panel? I can't find any bad wires anywhere. Anymore suggestions?
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Wednesday, May 31st, 2017 AT 7:33 PM
Tiny
CARADIODOC
  • EXPERT
You may be down to substituting parts. The problem is the short could be on a circuit that is turned on by a module. That means the short won't cause the fuse to blow until that module switches on. That's where I was with the black wire. Perhaps Saturntech9 has some better ideas.
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Thursday, June 1st, 2017 AT 12:36 AM
Tiny
WILLIAM RANKEL
  • MEMBER
Well I was look at the HVAC service guide from Toyota. The condenser fan is activated by the A/C switch. Any possibility the fan could be causing the blow fuse? I didn't understand the Fuse guide.
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Thursday, June 1st, 2017 AT 12:50 AM
Tiny
WILLIAM RANKEL
  • MEMBER
Interesting! I just found on the Fuse guide in the Toyota service manual that the 10A Gauge fuse also protects the fans. I wonder if it is the condenser fan. Looks like I have work to do tomorrow after it stops raining.
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Thursday, June 1st, 2017 AT 1:02 AM
Tiny
CARADIODOC
  • EXPERT
A fan motor can easily draw more than ten amps so they are commonly protected with 20 or 30-amp fuses. I would expect a ten-amp fuse to protect the circuit that runs a relay for the fan. Relays draw very little current.

Regardless, I'd unplug the fan motor and see if that solves the problem.
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Thursday, June 1st, 2017 AT 1:13 AM

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