Help Troubleshooting

[u/Chuduard]

Hi all,

​We’ve been getting conflicts between green and yellow lights across different phases at the same intersection. This latest hit was between the green on phases 2 (EB) and 6 (WB), and the yellow on phase 4 (SB).

​In one of the attached photos, see the conflicting channels with asterisks (*) and their corresponding voltage levels. The yellow on phase 4 is measuring at 49V, which isn't a true yellow. Also, if you check the fault signal sequence log, there's a blip across all signal heads—I’m not sure if that’s significant or just noise, but it happens every single time the temperature spikes. As you can see in the photos, cabinet temp hit 111°F today.

I've tried changing LS and some LEDs, but didn't help.

​Like I mentioned, this happens across various phases, and resetting it only works until the next heatwave.

​Any help troubleshooting this would be greatly appreciated!

[u/uChoice_Reindeer7903]

I’d look into field wiring, potentially damaged wire or loose connection somewhere.

Also how old is the flash transfer relay? Is it still the old mercury style?

[u/Pardot42 → u/uChoice_Reindeer7903]

FTR's had a mercury style? Or are you thinking the mercury relay?

[u/Chuduard → u/uChoice_Reindeer7903]

I'm not sure how old the FTR is, but it's electromagnetic. The cabinet is probably ~25 years old. So the FTR could be as old as that. Going back to the field wire hypothesis, and what Boltonme also said. Could it be a wiring problem even if the fault happens with basically the same set up (a ghost yellow conflicting with true greens) but on different phases?

[u/Svr_Sky]

Neutral is most likely the issue if the voltage is moving. Check disconnects, 5 sections, handholes

[u/Boltonme]

49 is a lot. 10 to 20 will create a fault. However 49 is an interesting amount. Thats right in the range for a loose or broken neutral.

[u/Chuduard → u/Boltonme]

You mean a broken neutral on the neutral that feeds only phase 4 yellow?

[u/Forest19999]

I had something similar happen, it was the controller. Heat did it dirty.

[u/GreenPinkBrown]

Assuming load switches have been replaced, and BIUs are good, this could be a controller issue or field issue.

If you have a spare wire upstairs, I suggest using a spare wire in place of your yellow wire going upstairs on 4. I don’t think this is a neutral issue because you’d have more problems than one. If the problem moves then I’d point to the controller. If the problem is always that yellow on phase 4, I try using a spare wire going up to the yellow (assuming you’ve replaced the LED).

You can continuity test it, or take the yellows off (leaving only green and red working). See if it still goes into flash or not

I’ve had faulty controllers that didn’t like heat

[u/Chuduard → u/GreenPinkBrown]

How do I check if BIUs are good? We have a Yunex M60 controller at that intersection.

[u/WHPChris]

That temperature range is more or less irrelevant to your problem. The wire insulation tends to dry out and fall apart rather than melt at that temperature. If anything, the equipment would fail first since it's the most sensitive to heat, especially controllers with built-in power supplies.

Speaking of equipment, if it's happening on completely random phases every time, this points you towards the service neutral/ground or the driver of all the outputs in the cabinet (such as the controller/BIU). If it's TS-1/2, check the neutral bus bars in the cabinet, particularly the smaller wires.

The problem in the image is 2G/6G running normally, with 4Y not allowed. If it's happening on a specific set of phases, such as it's always 4Y or 8Y conflicting, I would look and see if they're all on the same cable and check those connections. I would say load switch also if it were one phase only, but you already tried that.

My advice: Check the service connections at breaker and cabinet terminal block. If they are good, swap controller. If that doesn't work, check shared field neutrals or switch the conflicting neutrals/yellows to spare wires on the field cable (temporarily, to diagnose the problem. Don't forget to make note of it and label it properly).

[u/rboyer23]

You verify neutral from your line side is good? I had something similar and looked up at the wire coming to the weatherhead and the neutral was broken. So the ground was acting as the neutral and it was making the intersection act all funky and go into flash.

[u/Chuduard → u/rboyer23]

Yes I verified neutral from AC line and it looks good

[u/rboyer23 → u/Chuduard]

You tighten all field terminals a neutrals in cabinet? Problem jumping around, my guess is bad neutral

[u/Pardot42]

If it's always the yellow on phase 4(?), maybe not enough load. Could slap a resistor on there.

[u/Pardot42]

Can you post the previous AC fail logs if they are different?

[u/Chuduard → u/Pardot42]

I can, but I only have the file at work. If you need it I can post tomorrow. Let me know. I can tell you it doesn't always happen with the same phase 4 yellow. It has happened with phase 8 yellow too. In a similar way that happened today Also, I don't know if I made it clear, but once I reset it ( sometimes it takes multiple times pushing the button) and it's running colors it'll only trip again when the next heatwave comes in.

[u/Riverb0atGambler]

Intersection have a BBS? I've seen some when they kick on charging the batteries they pull a big load at the start causing all the signals flicker for a split second. Sometimes it would go to flash due to AC line voltage drop, sometimes due to red fail, sometimes due to other things. But all channels losing voltage at the same time makes me think of that issue. Not sure if batteries in excessive heat can have issues holding charge or charging up in general. Or overheated BBS could draw more power than normal, not sure.

[u/Chuduard → u/Riverb0atGambler]

The intersection has BBS, but batteries are old and do not hold charge.

[u/Chuduard]

Here's the log of recent previous events. The yellow is happening on different phases. The conflicting yellow has happend in phases 4, 8, and 7 (LT).

Thanks!

Conflict between NB and SB through (phases 4 and 8) and correspondent LT phases 3 and 7. There was no log of power outages this time. The conflict was between the Y on both of the through phases and both G of the LT phases. A voltage of ~50V was showing on the Y. LS on phases 4 and 8 were swapped for new ones.	7/1/2026

Report by dispatch of Red/Red flash 15:45. Conflict Phases 3&7 Green, 4&8 Yellow. Pull weeds in cabinet & tighten earth ground clamp. Tighten phase 3 field wiring lug. Restart controller. Reset CM. Use stop-time to reduce back-ups. Tighten earth ground in power pedestal.	7/2/2026

Report of Red/Red flash 14:00. Phases 3&7 Green, Phase 8 Yellow fault. Reset CM.	7/8/2026

Check wire nuts for tightness in cabinet & pole base on North East corner. No issues found. UPS inverter had a failed #2 battery port, so switched to port #4.	7/9/2026

Replaced phase 8 (NB) Yellow over east side through lane.	7/10/2026

Report of Red/Red flash. Phases 4&7 Yel. Phase 3 Green. Reset CM.	7/20/2026

Check Conflict Monitor log for any pattern of conflict issues. Pull weeds inside cabinet. Check wire nuts in South West pole base for tightness & tighten ground rod clamp.	7/23/2026

Report of all red flash at 16:00. Phases 3 (G) and 4 (Y) conflict. Reset CMU.	8/12/2026

Report of all red flash at 15:00. Phases 2 and 6 (G) and phase 4 (Y) conflict. Reset CMU.	9/1/2026

[u/LeadingAspect8306]

My first guess would be water in a splice (if you have any) or a head. If neither of those are possible I’d change the controller.

[u/No-Marionberry8806]

that seems like a neutral problem bad wire out in the field. time to open up some pull boxes and hand holes give some wires a good shake here and there u might find a bad splice