I recently switched the front turn signals/DRLs on my 99' C5 Corvette to LEDs and used the Envy Hyperflash Harness. Everything seemed to work fine. A few days later I got around to doing the rear tail lights/turn signals and they seemed to work at that time, but I did not immediately drive the car. I also put in LED side markers front and rear as well as LED tag lights and reverse lights.

I did drive it today and there is a problem. It was dark enough when I left the house for the headlights to automatically stay on most of the ride to work. Eventually, the sensors turned off the headlights and when I parked at work I noticed I had lights flashing - DRL/front turn signals, fog lights, front and rear side marker lights, rear tail lights/turn signals, and dash lights. If I put the headlights on, the flashing stops. If it turn on the hazard flasher, either with the headlights on or off, the hazards hyper flash. I checked the battery terminals just to make sure they were tight (I've had funky things happen electrically when they were not totally torqued down), but that didn't make any difference. I had to get in to work so couldn't do much more.

When I hit the lock button on my fob, the panic alarm went off. I do have a Window Valet so I had hit it multiple times to put up the windows. Got it all stopped and tried a second time and same result - panic alarm.

Does the hyperflash not cover the rears? Is some other workaround needed for the rear (like inline resistors or another harness)? Could it be that the hazard flasher unit is bad or going bad, which I've read can be problematic? I will experiment by pulling the rear LEDs and putting the old bulbs back in to see if that makes a difference but anyone with any ideas please chime in.

K9Leader
Red cars are faster.

 

I would think the Hyperflash Harness should have cured those issues.

I have switchback DRLs and Modified Halos in the back as well as LEDs everywhere else inside and out (excluding the headlights and fog lights). I haven't experienced those problems with my set up.

 

^Same here without issues.
Possibly unplug the battery to reset the computer and see if that helps. It may have gotten erroneous information while you were doing the swap.

 

Solved (I think). Pulled all four tail light bulbs and put back in the old incandescents. Alarm did not go off when I hit the lock button. Put the LEDs back in one at a time until I found the one that makes everything go funky. So right now, the three good LEDs are installed and one old incandescent. LEDs are Sylvania Zevo which are supposed to have a lifetime warranty - now just have to figure out how to get it replaced under the warranty.

I found some other posts about the alarm going off with the lock button and it was something faulty in the newly installed tail lights (Halo LEDs).

K9Leader
Red cars are faster.

 

 

I had Issues when my 3rd brake light died. For some reason the brake lights are tied into the ABS warnings.

 

Okay, so most of the problem resolved. Alarm problem is gone but still some flashing of the dash and HVAC lights. When the headlights go off, the dash and HVAC lights keep flashing, first fast, then gradually slowing, and finally stopping.

K9Leader

 

A Hyperflash Bypass Harness will not impact your Emergency Flasher as the Hyperflash Harness bypasses the Emergency Flasher and uses a digital flasher which handles LEDs.
I also had similar issues on my 03 when I installed LED rear tail light/stop/turn signal bulbs. I tried several combinations with no results. I finally installed a pair of resistors into the rear tail light/stop/turn signals and all the problems went away. Never did find a solution that didn't need the rear resistors :^(
The odd thing was that the exact same rear LEDs were used in my 99 for over 5 years without the need for resistors

 

Drove it today and the flashing dash/HVAC continues to happen randomly. I will notice it flashing, then it gradually flashes slower and slower and finally stops. I was wondering if resistors in the tail lights would be necessary. JRPrich, you mentioned a pair of resistors for the tail lights - not four, one for each light? Or would one resistor cover both lights on each side?

K9Leader

 

I started with 4 resistors but after installing I tried disconnecting one per side and everything still worked normally. So I left it at 2 resistors.....the fewer the better IMO.
In my case, I only have resistors in series with the outboard light on each side.

If you do use resistors make sure you use a sheet metal to screw them to the metal bumper bar as these things will get very HOT and need a metal surface to help dissipate the generated heat.

 

Did you try disconnecting and reconnecting the battery to reset the computer.
Check the grounding point on the right rear where the harness connects to the frame.

 

It could also be as simple as one of the four rear LEDs is in its socket backwards.

I have had very weird things occur when one LED is in wrong.

Remove and reverse one of the rear LEDs at a time and test your system.
Once you have it solved, mark each connector and LED bulb with a Red marker to indicate which sides go together.

 

^To add to this check for corrosion in the sockets.

 

I agree.

Get some good electrical contact cleaner spray


Jim

 

Don't give up! There are many people successfully running LED's and when there is a problem it is usually one of the above mentioned.
If you do a search you will see a lot of similar threads.