Key-On 30 Amp (+) Power Source

[texasjammer1]

Hey everyone,

I'm in the process of installing a Old Air A/C & Heater system in my 1970 Ford F100. It calls for a "Key-On 30 Amp (+)" power source.

I've looked through the wiring diagram master (link below) but could not find a 30 Amp source. Am I missing it or is it not avail as a standard for these trucks?

If it is on the truck, where is it? If not, do you guys have a solution for installing a 30 Amp source?

http://www.fordification.com/tech/wirin ... master.jpg

Thanks everyone for your time and looking at this thread.

[Nitekruizer]

I don't know about a "30 amp key-on source", but an alternative would be to use a lower amperage "key-on" source to trigger a 30 Amp relay that would get power for the A/C & heater from the positve battery cable connection to the starter relay. If you do it this way, install a 30 Amp fuse between the main (#30) terminal on the 30 Amp relay and the battery connection. Wire #932 in that diagram could probably be used to trigger the 30 Amp relay.

[texasjammer1]

Thanks nitekruizer... appreciate it.

[bluef250]

another option is to install a relay and is actuated when the key in the on position. The ignition switches are already overloaded. An AC 30 amp load increases the load through the switch by 10 amps. The heater load is 20 amps. I would hope you would not use both heater and AC at the same time. Although I have been known to have both on.