Electical Gremlin!

[wjpatton]

Here's a good one: the turn signals in my '90 D250 work fine, but the hazard flasher circuit is inop (I've checked the flasher). BUT, when I turn on the turn signal (left or right) and THEN try the flasher, it works- provide the ignition key is in the "run" or "accessory" positio). When the ignition is off the hazard flashers quit working. How the heck does an ignition switched power source get to the "always hot" flasher circuit? Any ideas where I should start looking first?

 

[Bob Beauchaine]

My first thought would be the "combo switch" I have seen all sorts of posts with odd problems caused by this switch. I had a problem where my high beams would come on the minute I started my truck. The switch would also turn on the dash turn signal lights but not the turn signals. These switches were used on most Chrysler vehicles well after '93 so they should still be available - if you decide to go that route. If that turns out to be the problem you will need a locking torx bit to take ir off.

Bob

 

[Hoefler]

Check for brake lights, I believe the flashers and the brake lights are on the same fuse.

 

[wjpatton]

The brake lights work normal, turn signals work normal. 4 way flasher and turn signal flasher units are good.4 way flashers only work with ignition switch on and turn signal activated, either right or left (flashers added to opposite side of activated turn signal.) All fuses check good.

 

[Philip]

How did you check the fuses??

When you apply a turn signal and then the 4 ways work. Your crossing power from turn signals into the 4 way circuits.

4 ways are a constant powered circuit. They should work no matter where the key is located even if its in your pocket.

 

[DVolk]

If you know any one with a powerbrobe that might find the problem .

 

[wjpatton]

I just swapped out the old flasher units with new ones, pulled and inspected all the fuses. The fuses were all good. Guess it is time to do some serious wire bundle checking. I agree that the 4way flasher circuit SHOULD be powered all the time, and apparently is not getting power until I activate the turn signals and turn on the ignition key. Yippee!!!!

 

[Philip]

Use a meter or test light on the fuse. I have seen what looked like a good fuse bad before. The only way to tell was with a test light or meter.

 

[wjpatton]

So if I have a bad fuse or some other reason the 4way flasher circuit is not receiving power normally, I could be powering it from the turn signal circuit when I activate the 4way flasher button on the column! Right?

 

[Philip]

Yes the turn signal switch will allow power to cross circuit from turn signal to 4 ways when both switches are activated.

 

[DVolk]

Aperson might check any added on lights

 

[wjpatton]

Fabulous! This narrows down my searching!

 

[Philip]

Start with a test light at the fuse. The go to the flasher. Then pull the column covers off. Find the wire from the flasher to the column. Check that wire at the multi function switch for power.

If you have power at the multi function switch. Then the switch is bad.

Start at the fuse block first. Its easyer then head towards the column. Your showing a 90 model in your sig. I don't have a wiring diagram for that year range.

I am betting its before the multi function switch. A long time ago there was noted problems with wires chaffing inside the column covers.

 

[wjpatton]

TDR rocks! Starting with the easiest and cheapest things first, although the fuses LOOKED good, I replaced with new ones, and wow- problem solved!! By process of elimination and playing with the old fuses, the old 4way hazard flasher fuse was bad. Even under bright light I could not see there it was bad, but it sure was! Thanks guys for all the ideas, it was truly a simple fix. I had replaced the flasher units to no avail, but because the fuses LOOKED good, I assumed they were. There goes that old saying about "assumed".

 

[Philip]

I found the same issue with a fuse in a friends truck. Now for the story. One friend had the truck for 5 years. He drove it all the time without a speedo. He sold it to another friend. That person wanted a working speedo. So after doing some troubleshooting. I found his fuse was the same way. It looked good. It would not power the circuit. It was a open fuse.

 

[DVolk]

Anoutherr thought if the cab has cracks and is leaking water the wiring could be shorting from water !!