blinking instrument lights?

[tarafied1]

Hey,
I'm new to this forum but Dave Sanborn got me interested in checking it out.
Anyway, I have a weird blinking instrument light problem. I have a 67 Mustang with 67 Cougar tail lights and the Dynomite sticks that make them sequential. When I am at a stop light for a mintute or so the instrument lights start to go out and they do come back on but not at any regular intervals. I have replaced the headlight switch. What else should I be looking at? Is it because I have added 4 extra tail light bulbs?
Thanks in advance for your help...

[AzPete]

Sounds like an extra load on an already weak system. Might have better luck if you try adding some relays to power the extra lighting in the rear. Not sure if it would work but it should be like the headlight relay package. The turn signal power activates a relay and that supplies power straight from the battery to the signals. Flasher should still work. This is just a thought so .... Also, make sure all your grounds are good and get a larger alternator.

[tarafied1]

What do you think is actually happining? Fusable link tripping out? Would the bigger alt simply provide enough juice if it turns out ground is okay? I'm dangerous when it comes to electrical stuff, is there somewhere I could look up how to wire the relays?
Thanks for the quick answer!

[Fast68back]

Jump down to the tech articles, there is a post about brighter headlights, it explains the relay install

[tarafied1]

Cool, thanks!

[daveSanborn]

When I am at a stop light for a mintute or so the instrument lights start to go out and they do come back on but not at any regular intervals.  What do you think is actually happining?

More details please....

I assume that since these are the instrument lights we're talking about.... this only happens at night.... when the headlights/parking lights are on?

Without any other information, I'd have to say that the ALT at idle (while sitting at a stop sign/light) is producing it's absolute minimum usable power.  Under this condition, electical devices can (and will) stop working or work intermittantly.  If you install a headlight relay, which will dedicate battery power to the headlights through the + side of the starter solenoid, I'm venturing to guess that this will correct the fading/fluctuating instrument lights.  Halogen headlights are notorious for overloading 1960's wiring/ALT output.

Stepping up to a higher amperage output ALT probably wouldn't hurt either.  Are you running a stock ALT now?

[tarafied1]

Yes Dave, this only happens at night with the headlights on. I do have Halogen headlights also. It is a stock alternator. Idle is about 800 - 1000 rpms (lumpy cam). There is no radio or AC or anything else to draw from the system but I guess the extra tailight bulbs and the headlights might be enough to overload the stock Alt.

[daveSanborn]

Dedicate your headlights with a relay as discussed in the tech. section and I bet this problem is solved.

[tarafied1]

I will do that this weekend!

[tarafied1]

well the relays made the headlights brighter but didn't fix the blinking. It seams less frequent but in fact I have discovered that when the dash lights go out so do the tail lights. I might try relays on the tail lights too.

[daveSanborn]

Craig,

The taillights shouldn't draw enough power to require relays.  Didn't you install all new wiring on your car?  This is starting to get weird.

[tarafied1]

no, it's 40 year old wiring except for the ignition, tach and a few things like the 4 headlights, and extra taillight bulbs. Could it be the Dynomite sticks I'm using for sequential turn signals? It only happens when I'm sitting with the brakes on for a while (at night). Maybe something in the turn signal switch, brake light switch?

[Fast68back]

How do the dynamite sticks ground? To the taillight panel?

[tarafied1]

yes

[Fast68back]

Have you tried grounding them somewhere else? Is your battery in the trunk?

[daveSanborn]

Could it be the Dynomite sticks I'm using for sequential turn signals?

Below is the link for the Scott Drake sequential flashers I used on my sons car.

http://www.scottdrake.net/prod_details.aspx?prod_id=6800&breadcrumb=Electrical+%26+Lighting+%3a%3a+Tail+Lights+%26+Back+Up+Lights+%3a%3a+Sequential+Control+Module

Are these the ones that you're using?

IIRC, a separate 12v power wire had to be run from the fuse panel back to the units.  I've been trying to find an on-line schematic for these units, but haven't found anything.... yet.  This separate 12v power source requirement leads me to believe that the units themselves act as relays in addition to the "sequential" function.

I have the printed instructions at home and I'll try to round them up to refresh my memory.

[AzPete]

From the previous posts, it sounds like the flashing is not in sequence with the tail lighting/signals. I would disconnect the tail light system completely and see if the dash lights still flash. Might help figure out where the problem is.

[tarafied1]

The battery is in the trunk, I haven't tried grounding them anywhere else yet, but that is a good idea. It would be easy to ground them right to the battery. Since the car has been painted maybe I don't have a good ground on the tail light panel.
Dave,
No those look different than the kind I have. I will see if I still have the info on them, I bought them a long time ago.
The blinking or shutting off doesn't happen when the turn signal is on, only the brakes. I drove it around a while last night and it didn't happen but it did it once on Saturday night after I installed the relays. I think the relays helped because it used to happen at every stop light if I was stopped for a minute or more. It also doesn't happen when I am slowing down with the brakes which leads me to believe the Alt may be part of the problem. I have March aluminum pulleys that may underdrive the Alt a bit. Since I put in a 67 Cougar Tach I don't have the amp gauge (which is probably useless anyway). I will hook one up and see if it's too low. I did sit in the car with the lights on and the brake with out the engine running and it didn't happen. Not sure what that means.

[daveSanborn]

Its sounding more and more to me like an ALT problem.  The OEM ALT just isn't making enough power at low RPMs to power everything it should be powering.  Is it an old ALT?  Bring it down to AZ and have them bench check it.  Their bench check will reveal how many amps it's putting out.  Then try one of their store stock new units and see if the new unit significantly outpowers your original.  It may be something as simple as an ALT swap.

[tarafied1]

I replaced it and the voltage regulator last fall. They are stock OEM type replacements. I think they are even from AZ.

[AzPete]

I would get an updated electronic voltage regulator. Did that on my '66 and it made a world of difference and there was nothing wring with the original one.

[tarafied1]

I would get an updated electronic voltage regulator. Did that on my '66 and it made a world of difference and there was nothing wring with the original one.

Now that you mention it, I do have one of those.

[tarafied1]

Well, as you might remember, the turn signal eventually fried. I replaced it. I also put the stock crank pulley back on to speed up the ALT at idle. I added a ground to the tail lights. I still have the problem. I have added a fan relay today along with a temp switch. Everything else seems to work fine, this one is really got me stumped. :expl

[AzPete]

Is there a difference with the engine running or with it not running and just the key on to get things working?

[tarafied1]

well I just went and sat in it, with the engine off. It still does it, I can hear what sounds like the instrument voltage regulator making noise then the lights go off. It doesn't do it right away, like it has to get hot. It will also do the same thing with the lights off, with the garage door shut I can see the brake lights start to flicker and I hear the same sound. It sounds like its coming from behind the insturment panel.