rover67
SILVER Star
I did a search a few nights ago and bumped into the answer but i can't find it tonight... What two wires do I short on the plug to bypass the little RPM control box?
AC Control Box Bypass
- Thread starter rover67
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run a jumper between the yellow wire and the black/white wire.
But it also bypasses the thermistor and pressure switch.
But it also bypasses the thermistor and pressure switch.
kevinmrowland
Forum Lifer
It isolates all the amp functions. You push the AC button (yellow wire) and is send power directly to the AC pump clutch (black w white wire).
You shouldn't run like this indefinitely since your AC will not cycle, it will just run & run, bad for everything in the system including how well it cools.
You can push the button in then out every 30 seconds o so every time you use it to approximate the function.
Works very well as a field fix and to help diagnose problems.
You shouldn't run like this indefinitely since your AC will not cycle, it will just run & run, bad for everything in the system including how well it cools.
You can push the button in then out every 30 seconds o so every time you use it to approximate the function.
Works very well as a field fix and to help diagnose problems.
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It isolates all the amp functions. You push the AC button (yellow wire) and is send power directly to the AC pump clutch (black w white wire).
You shouldn't run like this indefinitely since your AC will not cycle, it will just run & run, bad for everything in the system including how well it cools.
You can push the button in then out every 30 seconds o so every time you use it to approximate the function.
Works very well as a field fix and to help diagnose problems.
Kevin-
Any idea why the little CSV (?) switch that controls the idle up on the carb isn't receiving a signal? Also, would replacing the AC dryer improve function of the overall AC?
Thanks!!!
kevinmrowland
Forum Lifer
Does the rest of your AC work? You can check the other end of the circuit at your amp, the idle up is controlled by the solid black wire, you can see if it has volts when the AC is cycling (not just on, but clutch actually engaged)
If it does not have a signal coming out of the amp you could jumper from the clutch wire to the idle up wire because that is all that happens in the amp.
I would also check that the valve is not culprit, apply power and check that the valve opens by blowing through it. Also be sure that the actuator arm is actually not moving when the clutch is engaged, your throttle position screw could just be way out of whack and the valve might be working just fine.
The dryer does tend to clog over time, especially after the system is opened up, so if the dryer is clogged, then yes, replacing it will help.
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Thanks!
The above statement would be true for orfice tube type A/C system that uses a pressure switch to cycle the compressor clutch to keep pressures equalized.
BUT, our 60's use an expansion valve to do this function, and would be ok to have the compressor engaged all the time. Many cars with OEM expansion valve systems have the compressors wired to be on all the time. I currently have my 60 set up this way.
The 60's AMP box, thermistor and pressure switch are nice features.
You have the safety of not burning up the compressor if you run out of refrigerant (and oil) and someone runs the A/C on an empty system.
Your engine RPM's won't drop at idle, and if your evaporator ices up (like that will ever happen) it will disengage the compressor until it deices.
rchalmers3
I speak Toyota
FLCruiser, what about freeze protection? Dosen't cycling the compressor prevent a frozen evaporator and therefore improve cooling?
Rick
I don't know about all that, but when I bought my 60, the A/C switch was wired directly to the compressor, so the compressor was always on. On the highway, it would "freeze up" and stop blowing until I pushed the blue A/C switch and let it set for a few minutes.
I disabled that setup, and now it cycles like I think it should. My system has been converted to R134m if that matters.
I agree. But on our exp valve system, the only times the compressor will cycle for this purpose is if the thermistor detects the evaporator is freezing up or getting too cold, or pressure switch detects incorrect pressures. That usually happens if the system is starting to get low on refrigerant or is under filled, or the exp valve is out of tolorances.
kevinmrowland
Forum Lifer
The 60s have a very nice (mechanically) AC system, and there is no reason to not have it working properly. The AC will work fine with hard wired pump, put overall, it puts undue wear and tear on components and is generally inefficient. There is no need to have the pump running all the time, it builds pressure the system doesn't need, increases gas consumption and contributes to early pump failure. As a check and balance alone it is also a very good idea to keep the cycling functions working to help avoid damage to the system. AC parts are expensive.
