For A/C wizards, A/C system turns on/off/on/off after few minutes

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CarlosPTR210

New Member
Apr 5, 2006
435
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0
Calexico,CA
www.ptr.com.mx
Yesterday I send the car to recharge the A/C system (because during the engine rebuild the mechanics disconnect the compressor) :cry:

At the end of the process test the system for few minutes, everything was fine, no leaks, al pressures ridings keep normal, compressor normal, all good.

But after I leave the shop I Turn off the system ( no enough gasoline), so after the gasoline refill, I turn on again the AC system, but after few minutes, suddenly the system turn off :aigo: (the rpms at idle reduce), so I turn off the ac switch and turn on but the system doesn’t work, so I leave the ac switch on and after few minutes the system turn on (the rpms increase), and after few minutes turn off again, so the system is working in that way, on off, on off.

Yesterday the temperature was at 105 F.
Water temperature no more than 190 F
NO water in the heater system
New Fan clutch
All electric fan working

The mechanic checks the system and everything was normal, so he said than need to be a electric problem.

What can I do to try to find the root cause?

Thanks and sorry for the grammar :biglaugh:



 
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Who

Supramania Contributor
Feb 13, 2008
570
0
0
Palm Beach, FL
www.smartmediarepair.com
When you say the ac turns on and off due you mean the blower fan inside the car stops or the compressor cycles on and off?

If the system pressures are to low the system turns off. If the pressures are to high the system turns off. Did your ac guy put the manifold gauges on the ac system when you were having this problem? Or did he just assume it was electrical. Follow the TSRM http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?S=AC&P=1 Those high and low pressures readings are your usually your tell alls and your starting point The first test is pressures not electrical.

There are two switches on the high pressure side line. One switch is a high pressure condenser fan switch ( the one closest to the firewall) this switch turns on the condenser fans when the the pressure goes above 15kg (220psi). This switch only controls the condenser fans not the compressor clutch. If your condenser fans turn on than you now know that the high side pressure is above 220psi, ( or your car temp is above 215F)

The second switch is actually two switches in one. It is a high and low switch. On the low side. If the pressure goes under 2kg (30psi) the switch will open and the compressor clutch will disengage or stop working. On the high side of the same switch. If the pressure goes above 27kg (374psi) the switch will open and the compressor clutch is disengaged as well. http://www.cygnusx1.net/Supra/Library/TEWD/MK3/manual.aspx?S=Main&P=145
 
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