2nd Gen Non-Engine/Transmission Battery disconnect Flasher replacement

[czahnle]

Hi, I have a question. Why does the service manual say to disconect the battery when replaceing the flasher/relay ? The reason I ask is this. I have a 98. 5 24 valve and a service body on it. The tail lights on the service body are standard round truck light mounted in rubber. I replaced them with LED. This is not just a 1157 bulb replacement. Mine have about 15 LEDs inside of the sealed unit.

Everything was fine after replaceing for about a week then I hooked up to my trailer and towed for a day. After disconnecting my flasher flashes at twise the rate on both sides (No bulbs out) I read on the boards about our special flasher/relay and how it senses low resistance as a bulb out and flashes fast. I understand the LEDs are low resistance. So, I looked up the flasher in the SM and it says to disconect the battery first. Why?

Is this reseting a computer somehow? Will I be able to run the LEDs with this flasher?

Thanks for any help

 

[Thomas]

I understand the LEDs are low resistance.

Actually I think they are anything but low resistance. Low resistance=high current, something the LED's eliminate.



The problem of the OEM flasher + LED's has been hashed out here before. I don't recall any solution other than coming up with a way to let the OEM flasher see more current. Try using the search feature.

 

[czahnle]

Thank you Thomas for your reply

The stop/tail light bulbs I am talking about have 44 LEDs in them. Current enough I wonder.

Also why the battery disconnect in the service manual?



My searches all return stock tail lights.



Thanks



Chris

98. 5 24v

 

[DKlimas]

I believe the main reason for the warning to disconnect the battery, (notice that this statement appears in just about all of the electrical remove/replace sections), is to prevent someone (anyone) from inadvertently shorting or otherwise messing up the electrical system(s). Remember these trucks have many sophisticated electrical and electronic systems. Another reason, especially when working on the electrical systems in the cab, is again, to avoid inadvertently, triggering the airbag system. As far as the flasher is concerned, I believe you can get a replacement flasher for the low current LED lights...



Dave

 

[Thomas]

Ditto on the CYA aspect of the warning.



Shelby Griggs (still active on this board) spent many hours searching for a solution to the LED/rapid flash rate problem. Perhaps a PM to him can give you some guidance.



Good luck.

 

[OTRPU]

And if you find out anything come back and post the results please. I'm interested in this too, have repaced all my cab ID lights with LED's, and have additional LED's on the sleeper extension. Want to get LEDs for the tail/stop lights if I can. At least I THINK I want to do this, depending on the results that get posted.



Cheers,

Steve J



On the road, draggin a 5er through Indianapolis, IN on way to Oakwood, GA Monday, will overnight at Carnesville, GA Flying J

 

[Josparkz]

Anybody take their meter and see how the resistance compares with a stock light?

I didn't realize we had a trick flasher.

There are a couple of websites where all they sell are LED lights. You might could find out something from one of them.

 

[Shelby Griggs]

The LEDS draw low current, which the stock flashers see as a bulb out condition and then flash at double speed as a warning to the driver. The newer trucks, starting in 1999 or 2000 or so and through 2002 at least use an electronic 5 lug flasher, using the same device for both turn signals and hazards. The older trucks use separate flashers and the rapid flash rate can be cured with a heavy duty flasher. In all of my reasearch, I never found a plug in replacement for the newer trucks that cured the problem. For a while I added some resistance load to the circuit using low ohms large ceramic resisters, but this pretty much defeats at least one of the benefits of the LED lamps.



I finally had another member who is quite savvy with electronics do a little reverse engineering on the stock flasher, adding a potentiometer that allows me to dial the flash rate to whatever I want. Has worked good with no problems for over a year now.



Shelby

 

[czahnle]

Thanks for jumping in Shelby. I tried to PM you last night but your PM box was full. You and the rest are right in that the flasher needs to see more load. When I plug in my trailer with one more stop light on each side the turn signals flash right.



An over the road trucker friend suggested that I put two sealed waterproof red marker lights tucked up under the bumper shining down when lit. Wire them one to each stoplight. It sounded a little crude to me but he invited me to his yard that night and I saw he had them on his trailer and how they worked. It didn’t look funny at all. When the brake lights came on it looked like a big reflection. Of course there are 8 or 10 brake lights back there. This trucker is Mr. Lots of lights on his rig.

Anyway I think I will try it.



Thanks for all your input everybody.

 

[daveshoe]

I have service body as well. Truck came with regular voltage lights. I spliced into the wires after the lights and LED's flash normally. Ya could simply add a regular bulb in the line inside the utility body to gove the resistance you need. Not elegant ,but should work.