National Tripical Accessory Wiring Help Needed

[subtroll]

For more than two months I have been plagued with intermittent interruption of several dashboard Accessories...A/C Blower, wipers, Mirror control and Jacks power. IF the blower doesn't operate with the key "ON", none of the four will have power. I suspect it is either sticky relays or poor grounds.

At startup sometimes all work fine. Other times none work at startup but may suddenly resume working an hour or two later. Often the next time the engine is started. The more days I drive in a row the more likely all will work every day.

I arranged a day at Freightliner Service Center (Gaffney) to correct but of course the last day arriving in Gaffney all was fine. Can't fix something that isn't broke.

I have the Freightliner wiring schematics but they lead only to Coach Connectors not the accessories themselves.Does anyone have National Wiring schematics? or help leading me to the panel or relays that would be suspect?

[dougrainer]

All the items you listed have nothing to do with Freightliner and its wiring harness. The items are controlled by National's wiring and control center. In your brand RV, usually by the Inverter/Charger is a shoe box size fuse/solenoid panel. THOSE solenoids and fuses control almost all of the items you are having problems with. The only thing that is suspect is the Wiper Control system and that is usually thru the Freightliner harness, but if it is dead and the others also dead, then it is not the Freightliner harness. Most Motorhome makers use a Chassis Ignition side wire to energize the Fuse/Solenoids for most of the non Chassis items in the Cab area, the items the RV maker installs. So, you need to find that shoe box size solenoid/fuse center and check the solenoids there. Doug

PS, I doubt anybody would have a National wiring harness schematic after the more than 10 years since national went under after

[wolfe10]

Sounds like the IGNITION SOLENOID. The key closes/turn on the ignition solenoid. The ignition solenoid, then supplies all those circuits that only work with the key on.

Locate the ignition solenoid and check it with a voltmeter. Should take under 2 minutes to test.

Ignition off= 12+VDC to only one of the two large lugs of the solenoid.

Ignition on= same 12+ VDC voltage reading at both large lugs.

If not, check for 12+ VDC at the small terminal (from the ignition switch). If two small terminals, one will be ground, the other from ignition switch. If only one small terminal, ground is through the body of the solenoid.

You can also test by verifying which small (or only) terminal comes from the ignition switch. Disconnect the wire. Use a small jumper wire (carrying very little current, so small wire just fine) from the large lug with power from the chassis battery. You should hear a sharp "click" and power should be passed through to the other large terminal.