[50srodder]

I need a CONSTANT 13.5 volts or preferably higher to operate the air ride solonoids on my custom dually. How can I best obtain that? Higher output alternator? Any suggrestions or sure fixes will be greatly appreciated.

[75gmck25]

Alternators are designed to respond to load. You will get 13.5-13.8 volts charging after you first start the truck because you drew the battery voltage down with the starter. However, once the battery is fully charged the voltage will probably drop to about 12.5 volts, which is will maintain the battery at full charge.

If the solenoids really need a full 13.5 volts all the time, you will have trouble keeping that voltage. Alternators can easily reach that voltage, but they don't keep it constant. Most car accessories have a minimum voltage requirement of about 11.5-12.0 volts, but will tolerate voltage up to about 13.8-14.0.

It is possible to get a regulated voltage of very close to a constant 13.5, but not with the voltage regulator a stock alternator. A higher amperage output alternator probably won't solve the problem because it will still allow voltage to drop below 13.5.

Bruce

[vicrod]

Products designed for automotive use are normally designed for the range of voltages described by 75gmc.
I guessing that the 13.5 volt requirement is really for the air compressor. The compressor will have a certain rated CFM output matched to that system (truck). If the voltage drops below 13.5 that the compressor won't deliver the CFM. However the compressor will run but it will take a longer time to reach operating pressure.
The solenoids require very little power and are only for control.
So the best way to proceed is to make sure the battery and charging system are in good condition.
Use properly sized wire and solid ground for the compressor power feed. And depending on the size of the compressor, a direct connection to the battery may be required.
Post the full spec on your system to allow more discussion.

vicrod