Electrical 2011 Coyote Crate Engine AC problem


New Member
Oct 16, 2018
London UK
Hi everyone, I am new to this site and am hoping someone can solve the mystery with my AC compressor.

So to start with I must confess I do not own a Mustang. I have a GT40 replica that has taken me about 5 years to build, I have installed a 2011 Coyote engine and is now almost ready to drive and hopefully put through the approval test soon. I have struggled with support on this issue from FRP and so thought I might try this site since it is frequented by more people who might offer different perspectives directly experienced from this engine.

Here goes. I bought the crate engine from CJ Pony and had it shipped to the UK, when I bought the engine I was aware that it did not have some ancillaries such as AC compressor and alternator so I went ahead and sourced these also, when ordering the AC compressor I read that it did not come with the clutch and pulley assembly so I ordered this also. The engine arrived and then a short while after so did the AC compressor and the clutch - pulley assembly. The compressor was complete so now I have a spare clutch - pulley assembly.

The issue is that when I switch AC on it pops the 30 amp fuse, the fan speed drops very noticeably also which would indicate a large draw on power. So it is wired from the 30 amp fuse to the heater fan switch when the fan switch is in anything other than off it provides power to the AC switch/thermostat from there to the trinary switch, if the trinary switch conditions agree then on to the AC compressor clutch. When i called a AC guy in to degas and fill the system he checked through the circuits and was happy, it still popped the 30 amp fuse when switched on. We then disconnected from the compressor mounted on the engine and connected to the spare clutch assembly I have and it still popped the 30 amp fuse. The AC guy had a new compressor for a BMW on his van and suggested we connect to that just to try, I de pinned the connector to my compressor and connected to the BMW unit with some small leads and when I switched AC on it energised the clutch, did not effect the fan speed and most importantly did not pop the fuse.

When I measured resistance through the Ford clutch coil it was about .4 ohms on both units but the BMW ( BEHR HELLA) unit measured about 4.5 ohms.

Any assistance with this is very much appreciated.
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Active Member
Feb 11, 2016
Can you run the AC clutch through a relay??

I remember that's how it was setup in my 2004 Marauder!!

Also, how can you charge the system without the compressor running??