Rv Headlights

Discussion in 'The Projects Forum' started by jpcj100@earthlink.net, Mar 27, 2008.

  1. jpcj100@earthlink.net

    Thread Starter New Member

    Mar 27, 2008
    Tha headlights on my motorhome are only getting 9v so I want to install relays to supply the full 12v. Along with the headlight supply I would also like to put in a ICC switch to flash the headlights at the truckers when they clear. So the relay will have 2 imputs on the dim side and 1 on the brights.
    What relays would be good for this project and source for them? What size wire from the relay? Will it need any diodes? The only load on it will be the headlights, dim and bright.
    I can get a good 12v supply.
    Thanks for the help
  2. mrmeval

    AAC Fanatic!

    Jun 30, 2006
    Why are they only getting 9V?
  3. KMoffett

    AAC Fanatic!

    Dec 19, 2007
    I agree with mrmeval. It sounds like you're trying to treat the symptom, not the problem. That extra 3 to 6 volts you're "not" getting to the headlights is being dropped somewhere...producing heat...probably at a bad wiring connection. Much easier to correct than adding a whole new system.

  4. SgtWookie


    Jul 17, 2007
    I agree with mrmeval and KMoffett.
    A few quick checks:
    1) With the headlamps on, engine running, measure the voltage from the headlamp's ground side to the engine block. If it measures under 0.5V, your ground side wiring is OK.
    2) If you measured over 0.5V in step 1, measure the voltage from the headlamp's ground side to the chassis. If you measure less than 0.5V now, then the engine ground strap is faulty or missing, and must be repaired/replaced. If your reading is the same as step 1, your headlamp's ground leads have a bad connection, probably where they screw into the chassis.
  5. DC_Kid

    AAC Fanatic!

    Feb 25, 2008
    is 9v normal? and you want to flick on/off 12v as a pseudo "bright"? if so just get some 10-25amp rectifying diodes (jc whitney has dual battery diode setups, etc). then just relay 12v directly to the lamps.