YKKVET

I've seen pros and cons on the hyperflash harness - comments
Mine are now blinking fast after changing the third brake light
All bulbs are new
2000 conv

dadaroo

The third brake light is LED. But it should not corrupt the turn signal flash rate. If I remember correctly you have to access the third light via the turn/brake lights. You may have corrupted the circuit.

Recheck the connections on the side you used to access the third light.

Also visually verify that the turn signals all work even if they flash faster. Front and rear.

YKKVET

All lights work
Saw a thread about grounds - going to clean all I can if that don't work I'll put in the hyperflash harness

dadaroo

Try using the hazards and see if you get the same flash rate.

YKKVET

The blink normal

dadaroo

That is what I figured would happen. When you use the hazards you split the front lights from the normal circuit thru the multifunction switch. I still think when you did the 3rd light work you introduced an issue. It is unlikely that something else happened at the same time, assuming the fast flashing happened right after the 3rd light work when you tried the turn signals the first time.

Here is the schematic:



Green and Yellow to the rear and Blue to the fronts.

YKKVET

Most likely - The third light was out for a while, must be Gremlins
I will add the inline hyperflash cable. What's another I have had the LMC5 bypass in for 2 years with no problem

dadaroo

The Hyperflash should help you short term but it is only going to mask the problem. You have a problem that you should not have and I expect at some point you will see the issue get worse.

I have seen stranger issues in these circuits. You might want to remove the 3rd light and see if it goes back to normal. Could be an issue with the LED back feeding an issue into the circuit. It is a free test.

Did you get a GM OEM LED or some generic that would fit?

YKKVET

Thought about discounting will do later this week
Unit was Generic
Maybe if disconnect works I'll get a GM

YKKVET

Couldn't wait
Disconnected third light - signals still fast

3sACROWD

You state "all bulbs are new". Are the new bulbs incandescent or LED? If you replaced with LED, that is the reason and you will need the hyperflash unit.

YKKVET

Standard no LED

dadaroo

Like I said before I have seen strange things where normal physics does not seem to apply, of course we know it does.

I still think you did something to the lights when you replaced the 3rd light. Hope you rechecked the connections when you disconnected the 3rd light.

All four turn/brake light bulb circuits go to the same ground which is shared by the other back lights. I don't think the splices or ground there is the issue

If it were me I would make sure when you apply the brakes that each light has the same brightness. Two person job.

If that does not show anything I would remove each bulb and do an ohmmeter test for resistance to ground from inside each socket.

Long shot might be some thing in the Multifunction switch associated with the front turn signal circuits but I'm just keeping that in the back of my mind.

Do what you can and I will scratch my head some more. Have you done anything else to the car recently that might be even related to the wiring? Hyperflashing is caused by not enough load drain/draw in the system to flash normally.

YKKVET

Replaced the hazard switch but that was after
I'll go through the bulbs
Thanks

YKKVET

FYI
Had the wife hit the brakes - inside left lamp goes from on to off, changed bulbs same result

dadaroo

Well I think you found the bad circuit. May be a bad socket. Check it out closely. If you don't find it I can tell you what I would do to diagnosis the issue.

YKKVET

I'll start with the socket and go from there. I'll let you know what I find, you've been helpful. Thanks

dadaroo

Glad to help.

Since you seem to have an issue with only one bulb, I am ruling out the Multifunction switch and the wiring up to the rear splice where the power splits to the 2 left bulbs.

If you want to discuss anything you can just PM me with your phone number. It is easier than writing.

SG Lou

Yup, Dadaroo is one in a million !