AC fuse blowing

[Iziks]

Factory Five AC kit. Got everything installed and wired. Pulled a vacuum and it held, so I charged the system. With AC running and car at idle, I am at 25 low / 250 high. Air temp was about 85. Everything seems to work fine and the air is nice and cold. System keeps blowing the AC fuse after 5-10 minutes. Any thoughts for me to try to chase down?

The compressor instructions said comes with oil. AC instructions say to use one can 1st charge, so I did that. Could there be too much oil?

The longest the system worked was when charging. I put the 1st charge (12 oz) can in with motor off. Then it ran fine for what seemed like awhile while I was charging the system until it blew the fuse. After that, just blows after 5-10 minutes now.

[michael everson]

I doubt its related to the charge. What amp fuse is it? Maybe go up 5 and see what happens. Maybe between the blower motor and the A/C clutch its just a bit too much for the fuse. How long will it run on low speed?
Mike

[Iziks]

20amp. I tried 25 after running out of 20 and still blew.

Come to think of it, I had fan on medium. Will try low.

[JimLev]

Is FFR still supplying Vintage Air systems?
My instructions say to charge the system with 28 oz of refrigerant.
IIRC the blower motor and the compressor clutch are on separate fuses.

[Mastertech5]

Did you evacuate the system for about an hour before charging it? This is necessary to remove any moisture and air in the system. Air or moisture will cause the pressures to be off. Does the low side pressure fluctuate or is it steady? It seems a little low, but still within limits. If you have moisture in the system the evaporator will freeze and cause a low low side reading and a high high side reading with the low side fluctuating low to normal as it freezes and then thaws from heat build up. Did you watch the sight glass on the accumulator/dryer and stop charging when the bubbles stopped? With the AC off the pressures should be the same and within about 3-5 degrees higher than ambient air temp with a correct charge amount. Higher than that, overcharge. Lower than ambiant, undercharge. I hope this info will help you figure it out. Trying the fan at different speeds and how quickly the fuse blows might give you a clue. Is the coolant fan coming on when you turn on the AC?, It should.

[Iziks]

Pretty sure sourced elsewhere now.
My instructions don’t provide specific oz. Just one can 1st charge and 2 12 oz cans.
Fan and compressor are on the same fuse. Here is wiring diagram from my instructions IMG_1618.png

[Iziks]

I did evacuate for an hour. But I may have used unvacuumed lines between cans. (I think I disconnected the gauges and reconnected at one time).
I did not check for bubbles until done. There are none now.

Thanks - I will check some things out and report back

Coolant fan is on with ac on.

[Mastertech5]

Try running the blower motor with the AC off. You need to isolate the different circuits. Check the wiring for the heater control valve for a chafe on the bracket, the edges are sharp. I put conduit over the wiring on mine. Trinary switch could short internally after the 10 minutes. The thermal expansion valve (thermostat) gets power through it and the blower resistor on the evaporator case and the blower motor itself. The clutch is just a electromagnet so there is no real load on it except the resistance of the winding no matter the charge. It could also short internally though after heating up.

[Iziks]

Checked pressures with AC off. They are about 12 over ambient, so I probably have overcharged. Kinda funny cause when the bubbles cleared, both low and high pressures were low - that was why I added more refrigerant.

The FF instructions were literally “ Charge the system”. Even after hours of internet research, Mastertech’s summary above is the best I found!

Anyway, off to shop to have some refrigerant removed as I have no way to do that at home that i’now of. Thanks for all the help!

[Mastertech5]

You can let it go into the atmosphre through the gauge hose, but that is very illegal. Save the ozone layer! They will evacuate the system completely and the machine will weigh it minus what's left in the hoses.which isn't much. Good luck. They can recharge it for you too but you need to know how much to put in. It will also remove about an ounce of oil or less. We used to get about $130 for Evac and recharge plus R134a at $15-$20 a pound. Glad I could help.