Electrical troubleshooting: Headlights SOLVED!

[Alec]

Hey everyone - I'm at 800 miles on my roadster and a new problem cropped up out of the blue. Normally I enjoy troubleshooting electrical systems, but given the possibility of disassembly of the dash etc and all the work involved (e.g. pulling off the steering wheel), I want to plot my troubleshooting steps correctly and need advice along those lines to avoid unnecessary work or time waiting on parts delivery.

My setup: Ron Francis Harness, Speedhut vintage gauges, Breeze LED headlights, IDIDIT relay, high beams wired to the Russ Thomson turn signal stalk momentary switch .
Symptom: Headlights abruptly stopped working at all, high or low beams. The high beam indicator lights also never come on. Everything else still works normally: both turn signals, parking lights, horn, all gauges, flashers, courtesy lights, EFI etc.
Steps I've tried already: With the headlights switch on, sticking my hands under the dash to wiggle wires and and connections to the russ thompson unit, random other locations where connections exist btw the IDIDIT box and the rest of the dash wiring. I also swapped in a brand new headlight switch (the standard AC delco switch clone from the complete kit) and it fixed/changed nothing. The headlight connections up front seem physically fine.

What are my steps, and thanks in advance to all of you electrical engineers! - Alec

192024

[rthomas98]

Question did you check the fuse under the dash? Also doesn't the breeze lights have an additional fusable link on them as well? Did you put a volt meter on the wire connections that go to the light to see if power is getting to them? If you have power there then you have an issue with the lights wireing or the lights themselves. Personally I do not change components until I have gone through with the volt meter on the connections to see what is and is not getting power. Don't want to add variables.

[Alec]

Question did you check the fuse under the dash? Also doesn't the breeze lights have an additional fusable link on them as well? Did you put a volt meter on the wire connections that go to the light to see if power is getting to them? If you have power there then you have an issue with the lights wireing or the lights themselves. Personally I do not change components until I have gone through with the volt meter on the connections to see what is and is not getting power. Don't want to add variables.

There is no headlight fuse in the panel, turn signals/marker lights etc, yeah, but not the headlights themselves. Given that both headlights are not working nor the high beam indicators, that rules out the headlights themselves, no? My logic says that it is something more central. But point taken about the voltmeter up front to check power/lack thereof, as well as good continuity to ground.

[Mike.Bray]

I'm looking at the schematic and the fuse in the BATT FEED section that's next to the flasher is labeled HDLT SW/RADIO MEM. 15A fuse.

Check that.

[rthomas98]

There is no headlight fuse in the panel, turn signals/marker lights etc, yeah, but not the headlights themselves. Given that both headlights are not working nor the high beam indicators, that rules out the headlights themselves, no? My logic says that it is something more central. But point taken about the voltmeter up front to check power/lack thereof, as well as good continuity to ground.

I circled the fuse to check below:

https://thefactoryfiveforum.com/attachment.php?attachmentid=192025&d=1699460391

[phileas_fogg]

I don't have anything specific to your issue, but I seem to recall reading about a relay in the headlight switch itself that would overheat and cause the lights to go out. The solution was to swap out the headlight switch. You've done that, so I don't think the internal relay overheating is your problem (just including the description so that the relay problem shows up in future searches).


John

[michael everson]

I would suspect the VW relay that triggers the high beams. First check the blue wire that feeds the high and low beams for power. In a quite garage, turn on the headlights then toggle the momentary switch. You should be able to hear the relay. I have had many of these fail over the years.
Mike

[Alec]

THat fuse is fine. The 2 red feeds TO the HL switch are hot. The black feed in that same female plug is grounded. All 3 leads to the headlights up front are cont with ground regardless of switch position.

[Alec]

I would suspect the VW relay that triggers the high beams. First check the blue wire that feeds the high and low beams for power. In a quite garage, turn on the headlights then toggle the momentary switch. You should be able to hear the relay. I have had many of these fail over the years.
Mike

Miek - I don't hear a click, but then again I never have. Which/where should I check the blue wire? Coming out of the HL switch the blue wire is hot when the HL switch is in the ON psotion. From there I don't remeber, does it go to IDIDIT or straight to the stalk switch? If the VW switch relay is cooked, where is that, how is it fixed? At the moment my only access is from below, and also I can access the proximal russ thomson connections throught the speedo hole (I unscrewed it and its hanging out).

[Alec]

More data: At the input to the IDIDIT relay pack - with the plug removed from the relay: All seems kosher. Its got 12v input, the tan wire which goes to the stalk switch DOES switch to ground when the button is pushed, which is normal/expected. Its got black ground. The HL input from the HL switch also switches hot with the switch turned on. ALL NORMAL. now it might appear that the IDIDIT relay output is not working. AGREE???

[edwardb]

To me all signs point to the Ididit module. :( The headlights are a direct wire from the ignition switch and have an internal circuit breaker in the AC Delco style headlight switch. None of the circuits on the panel or fuses are for the headlights only. Also, you don't have the VW style relay with your setup. The Ididit module replaces that. If you have voltage and ground going into the Ididit module and no headlight voltage coming back out... that's it.

[Alec]

I just ordered a replacement relay module and will swap them and test.if it works them ididit said I can send the bad one in to.them for testing and reimbursement. It's only 6 months old.

[maclonchas]

I know that Paul usually gives the best advice, but I would check one more thing in the IDIDIT relay circuit. If you used the wiring diagram that Ted G had shown in his build threads, there is a 30 A fuse from battery power to the IDIDIT relay. You should be able to check if you have power to the IDIDIT relay with a multimeter. If you have access to the connection you can also check in the front harness pigtail to see if you have power to one of the headlights. Also check your grounds for the headlights as they are notorious culprits for no headlights.

[edwardb]

I know that Paul usually gives the best advice, but I would check one more thing in the IDIDIT relay circuit. If you used the wiring diagram that Ted G had shown in his build threads, there is a 30 A fuse from battery power to the IDIDIT relay. You should be able to check if you have power to the IDIDIT relay with a multimeter. If you have access to the connection you can also check in the front harness pigtail to see if you have power to one of the headlights. Also check your grounds for the headlights as they are notorious culprits for no headlights.

In my defense, I said if there was voltage into the Ididit relay (the fuse would have to be good) but no voltage out (light grounds wouldn’t be in play) then likely the Ididit module is defective. Sounds like the OP is working with Ididit to replace and confirm. But all good. Electrical issues can be challenging and doesn’t hurt to check everything. In hindsight the problems are often obvious. But not until you find them. 😁

[Alec]

I actually said that above, that the relay unit is getting 12v and a solid ground, the stalk switch is also signaling the unit correctly, and if I drive 12v through either of the headlight out wires the lights work fine. It's the ididit relay. New one arrives this morning and I will confirm .

[Alec]

SOLVED! But it was not what I thought. I'll explain myself, and perhaps someone else can avoid this rookie mistake. I gave you some false data (unknowingly), which pointed us all towards the relay module. I swapped the IDIDIT module (which was overnighted from Summit) and it didn't fix it! I checked for a 10th time the input 12v to the module. The LED turns red and I get a constant tone (same way I tested before). The other possibilities here are a green LED and a fast beeping, which means ground, or nothing which means, no continuity to other power or ground. My circuit tester has 2 modes, 'test', and 'voltage'..... so I switch to voltage and I read 12v from the HL switch input, and 5v(!!!) on the supposedly 12v source to the module. My tester gave me a 'hot' signal despite there only being 5v on that input, not enough to activate the LED lights. I send in 12v, and it all works again. So how the hell do you 5v in a 12v car? You have a loose screw terminal on a distribution block on the firewall behind the dash. Loose wire = resistance and a voltage drop. I'm lucky things didn't worse (spark, fire etc).

One trick I learned as I fixed this connection: getting visual access to the firewall behind the dash, even up high, can be achieved by unscrewing the rings that hold in 1 or 2 gauges and pulling them out a bit. THis made me happy that I didn't go full OCD on the dash wiring and make everyhting super super tight which would have prevented the gauges to move much out of their holes from the front. My headlights work again. Thanks for everyone's input checking my logic and making other suggestions.

[maclonchas]

Alec,

Glad it all worked out. I found it hard to believe the IDIDIT device cratered so early in life (infant mortality) and that is why I was stressing checking the wiring at each section with a multimeter. I have burned too many times not checking the actual voltage and depending on the device to let me know that it detected voltage.

Cheers

Bill

[Railroad]

I have encountered 3 to 5 volts on a 12 volt system when the feed or ground is feeding through a light filament. I guess an LED light could present a similar issue.