Packard Forum Index » Modification Discussion

It's not an Inverter (as far as I know it doesn't actually invert anything). An Inverter usually refers to DC to AC conversion. A voltage step-up is more commonly called a Buck converter and are available on Amazon and elsewhere.

Incidentally I have an complete aftermarket ARA unit in case anyone is interested. I was told that it had been installed in a 1953 Mayfair.

Quote:
True. Converter is the better term for the modern 6 to 12v units. I too often use terminology more suited to the specialized high amp power supplies in some of the prehistoric equipment I used to work on.

Does anyone know how much HP the late model style compressors pull when operating at road speed?

Step up is Boost, step down is Buck. Boost is harder to find since the applications are a lot fewer... in general for multivoltage systems usually you'd run the higher voltage (e.g. 12 or 24V) and step down as needed (e.g. 5V for electronics).

Howard I’m sitting here trying to figure out if the gentleman converted from 6 v to 12v, only to drop the voltage back down by running the fan at medium speed (likely to limit the current). I must have been absent from class the day that HVAC blower motor voltage discussion took place. My ’54 Cavalier (6+) has a single 3/8 inch belt aftermarket AC system that works just fine. It’s a long belt installation that uses the power steering sheave. The clutch coil has a resistance of 3.6 ohms, which is the same as a 12 v coil in my ’99 Chevy. My evaporator does not seem to have any voltage converter . . . at least not obvious, and I’ve looked. My current thought is the highest fan setting in my car is providing 7+ volts to the blower motor, and that voltage provides enough air flow to convince me the AC is working just fine. I’ve had no success finding an aftermarket evaporator (or blower motor) specifically for 6 volt cars, but I have found a lot of threads that say a 12v AC can’t possibly work on 6 volts! I haven’t found a ‘wide-belt’ solution yet . . . maybe a double 3/8 system would mimic the look, but I suspect a serpentine pulley could be modified.

dp

I think he was referring to the dual shaft 12v blower motor as not having a 6v replacement and was probably the reason he automatically went for the converter. You are correct in that he is undoubtedly raising voltage then lowering again and could surely power the motor directly at some lower fixed speed. I started to do the 6v lower voltage with my repro prewar AC in the 47 which is based on a 12v modern unit. Was not happy with the airflow since the max speed was only about medium low. With the unit in the trunk I could not feel much air in the front. Stuck with 12v but then went with an automatic switching dual battery setup. Am rethinking that approach now if I ever decide to finish the project.

You can get 6v universal single shaft heater motors but not 6v dual shaft AC motors. The heater motor is smaller and not quite as powerful so only maxes out at about med high as a comparative speed. To run dual blowers with that motor would take some re-engineering and some kind of long shaft setup. It still might not be powerful enough in the end.

I also wondered about the single switch for everything and can only conclude he probably started wth one of the inexpensive aftermarket units with blower controls that use a rotary switch to do the on/off and select a fixed specific size resistor mounted in a module for 3 disceet blower speeds. He obviously eliminated that switch and decided to only power a single resistor at whatever speed. If he has a 10 amp converter then medium or low would be my guess because many of those AC motors exceed 10 amps when on high.

The long unsupported belt lengths if on the slack side can start to whip at higher engine speeds so that is the downside to the long single belts. If it wears and loosens and then whips too much it can pop off a pulley and do some damage. That would also stop the radiator fan and generator. Even though it was only the compressor, Packard had idlers on both sides in their long factory dual belt arrangement on the 53-4 units. I think an idler would be advantageous to any install that has a similar length but without one just keep an eye on belt wear and tension.

There are shops that can rewind a motor so probably converting the motor itself is the most direct route although I suspect it's quite expensive.

TxGoat; The web seems to think 3-5 horsepower is the range for AC compressors. As a first estimate the power should vary by speed cubed, and torque by speed squared, so if the 3-5 hp is for a higher rpm then at idle speeds the load is quite small. That by itself may explain why the compressor clutch in my ’54 functions so well, that is the Packard engine speed is quite low therefore the torque never reaches the design point of the clutch, and the fact that the current is essentially ½ of the design current the Packard’s slowness still wins the day.

Howard; The ‘under dash’ evaporator design places the unit essentially in your lap, with little or no duct loss. Perhaps in that configuration a low fan speed still results in acceptable air flow. In the unit featured in the video my bet is all of the controls are hidden under the added panels. The speed switch is set to medium (perhaps at higher speeds an in-line fuse complained), the temperature control set to maximum cooling (minimum temperature), and the single switch is controlling the power to both the blower motor and clutch (open loop unless there’s low & high pressure switchs). Note in the video there is little fan noise. Perhaps an e-mail to Vintage Air is in order.

dp

For whatever reason I got the impression that since he said the original front stuck out too far he had taken the original case off and eliminated the switches. He said he made the sheet metal that is there to be smaller and the filler panel above it to cover the gap. Since that space above is where he had hidden the converter maybe the switches are there too. Seems odd he wouldn't make them visible though.

On my '48 Custom 8 I converted to a serpentine belt and mounted the compressor on the driver's side of the engine above the cylinder head...and the 12 volt alternator below it. Here is a rather poor photo with the engine in a 'test' location...an extra brace for the radiator is not in the final installation. BTW Ron Davis fab'd a new aluminum radiator with two large fans for the final installation.

Attach file:

---

  image0 (4).jpeg (256.07 KB)