AC fuse blowing

Wobdog

Wobdog

a.k.a Mike
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My A/C fuse blows when I switch the A/C on high after a few minutes. AC does come on and blow cold air but after 2-3 minutes the fuse blows

Background:
The system was working normally before a recent 3-day, 500-mile drive. During the trip, I didn’t use the A/C compressor, but I did run the main blower on high with the fresh/cold air lever (right side) open.

Current issue:
Now, even with the main blower turned off and the cold air lever moved to the left, the A/C fuse blows soon after I engage the A/C. Ideas?
 
I have a blue 25 Amp fuse in fuse 8 location
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Mike
Yes original wiring and fuse block. Modern compressor. Do an AI search for 2800cs fuse diagram and the fuses are called out in E9coupe.
Dan
 
Sanden compressor can peak to 10 amps.
And the driver’s door window motor typically draws 10 to 15 amps during normal operation.
 
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I'd suggest try to isolate the cause component. If no meter handy can install in line fuse to compressor clutch to see if that is offender. How is the front auxiliary fan wired? Along the way sometimes get added to the clutch load instead of through relay with separate power supply. Is heater fan - your "main blower" visibly shutting off when you turn on AC? Console AC switch alternates between fans - maybe that is shorting. Has your rear defroster popped on unknowingly?
Presume you meant standard 16 amp red not 10 amp
 
Sounds like a bad AC blower fan
disconnect the black wire at the compressor and turn AC fan to high.
 
the fuse sticker on my 2800cs shows what Dan's shows - 25a. Mike, since you have xxxx432 and Dan has x394 ... and i have x487 CSA ... they should all be the same. 25a is the correct answer. the 3.0cs also uses 25a on fuse 8 for A/C

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Here is an update:

I changed the fuse to a blue 25A fuse. The system works fine around town and while idling, but when I take the car on the freeway, the fuse blows.

My suspicion is that the squirrel-cage fan spins faster at higher engine speeds and may be overheating or drawing excessive current.

A few other relevant facts:

  • The main blower is turned off.
  • The cold-air lever is moved fully to the left.
  • The squirrel-cage fan runs continuously, even when everything is switched off.
Does this behavior suggest a faulty fan motor, relay, or wiring issue?
 
Mike
So is everything off when it blows the fuse? AC controls all rotated counterclockwise?
Which fan is running constantly (AC Squirrel cage)? The fan switch should turn the squirrel cage fan off.
Heater fan is on fuse 9. The fuse 8 also controls driver side windows and rear defogger.
When the fuse 8 blows the squirrel cage fan stops?
 
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Dan Wood said:
Mike
So is everything off when it blows the fuse? AC controls all rotated counterclockwise?
Which fan is running constantly (AC Squirrel cage)? The fan switch should turn the squirrel cage fan off.
Heater fan is on fuse 9. The fuse 8 also controls driver side windows and rear defogger.
When the fuse 8 blows the squirrel cage fan stops?
Click to expand...
Dan
Looks like I was wrong. City driving did blow the fuse, I just checked the fuse box and fuse was just about to totally blow, see picture. It is fuse 8 that is blowing. When fuse 8 blows the squirrel cage fan stops. I am going to next try Don's advice of disconnectong the black wire at the compressor and turn AC fan to high. Is this were I disconect the wire (chat gave me this)?
 

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I wish mine was here at the house so I could take pictures. There should be a black wire running to the compressor with a terminal near the compressor you can disconnect. It should be about 8 inches from the compressor.
The compressor wire could black or red.
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Does that run to the compressor?
If so it looks to be a spade plug in terminal that the wire should pull out.
If you can't unhook it just try rotating the thermostat (temperature control) knob counterclockwise and then check to see if the compressor is on.
 
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The black wire from switch goes to the relay controlling the fan in front of the radiator. Unfortunately it also goes to the compressor so removing it from the relay still powers the compressor but now fan is off. See if there is junction in the wire to the compressor and unplug there.

That Chat GPT pic is wrong! It says the drier or muffler mounted on the fender is the compressor clutch.
 
I disconnected the compressor and the fuse did not blow even while driving on the freeway. I am assuming this indicates the problem is with the compressor? The compressor is new so what would be my next step?
 
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