My neighbor has an '89 auto D250. He brought it to me to fix his lights. He said that when you step on the brakes the front running klights come on . I pulled it in the shop and tryed it , nothing happened. I did notice that the dome & hood lights were flickering. I then turned on the headlts & the were flickering to ???. The cbls were corroded so I chngd them,checked voltage at battery& alt. Steady 14.5v. ??? I hit the brks agn; the run lts & dash lts came on, but not every time. I'm not sure the flickering and the running lts are the same problem. has anybody seen this before? I know from my experiance at the shop DC electricals are some of the worst.

 

Mine had a condition similiar to what you describe. I would be goining down the road and hit my hi-beams. The headlights would go out and the exterior and interior lights would flicker. When it was doing this, you could hear a circuit breaker throwing on and off by the fuse box. Sometimes it would do it, sometimes it wouldnt. I changed the headlight switch and checked the connections to it, the fuse box and the wire bundle going to the fuse box, all seemed good. After I put everything back together, it worked. Hasnt given me a problem since.

 

Check to see if he has changed a bulb lately.<br>I've seen this a few times before where someone used a single contact bulb to replace a double contact bulb.<br>

 

Check all the brake lite bulb assemblies for bad grounding. if the grounds are corroded you will get feed back from the brake lites through the park and signal circuits. Clean all the connectors and bulb contact areas. Using an Ohm meter check to make sure you have good grounds. When you reinstall, use some dielectric grease to keep the connections dry.<br><br>Also pull the harnessess to see if the plugs in the frame rails are tight and dry. There is one plug for each side.<br><br>If he has a trailer plug, pull that component apart and clean it out. I have had my brake controller flicker a couple times with the running lites and the plug was full of salty water from the road. Makes a really funny electrical gremlin.<br><br>Most of these symptoms you show are due to bad grounding in the light circuit.<br><br>J-eh<br><br>

 

Good ideas guys. You're right LilDog when you turn on one thing and another comes on it's usually feed back. Just thought there might be a common problem with these trucks to look at. <br> Okie, as far as the flicker. It's not really a flicker. It's more like a constant rise and fall in voltage. It happens all the time. It reminds me of the old gen. systems that would get bright and dim at idle only faster. This is what made me check voltage. <br> The front run lts only come on with brake lts occasionally. I did notice there is no bonding wire from the cab to eng. or batt. I'm going to make a jumper to see what happens. Thanks