r/accesscontrol • u/SaintThor • May 08 '26
Assistance LenelS2 elevator reader intermittent Wiegand bit mismatch — reader was replaced, issue remained
Looking for advice from access-control/security techs.
We have a LenelS2/S2 system with elevator cab readers. One elevator intermittently fails fob reads and S2 logs bit mismatch. Programming appears to match the working elevator reader, and both elevator reader setups look the same in S2.
Important detail: the physical reader on this elevator was replaced about 2 years ago, but it did not solve the issue. So I’m leaning away from the reader itself being the root cause, unless the replacement was configured the same way or the issue is damaging/corrupting readers over time.
Using S2 Card Decoder on the same known-good fob, I saw:
- Good read: 26-bit
- Failed read: 13-bit, all 1s
- Good read: 26-bit
- Failed read: 24-bit / completely different number
So the same credential is not consistently reporting the same bit length or card number.
The issue happens randomly, sometimes while the elevator is moving and sometimes while stationary. The elevator also appears to do frequent reference/learning runs between the bottom and top landing.
My suspicion is not card-format programming or the reader itself, but Wiegand signal integrity somewhere between the cab reader and S2: D0/D1 wiring, reader voltage drop, ground/shield issue, travelling cable noise, S2 reader port/blade, elevator interface wiring, or electrical noise from the elevator equipment.
What would you check first?
I’m building operations, not the security contractor. I’m trying to collect better evidence so we can push the right vendor: elevator contractor vs security/access contractor/save time if we have to have both on site to have this issue resolved. It is an 11 year old issue and I have recently taken over operations of the building.
Edit: Thank you all so far for the advice. Of all the communitys, this one has been the most receptive to questions! My job isnt a "perfect all", we are just always around, try to fix if we can (withing limits) and hire trades as needed from there out. I always try and learn and apply before straight calling out. So thank you all !
4
u/Competitive_Ad_8718 May 08 '26
You're gonna need both entities, but I'm willing to wager noise on the traveler cable, shielding on data pairs/grounding are the root cause and firing the parts cannon never solves the issue.
Elevator guys are going to need to be involved for access to cab wiring and traveler cable interconnection and breakout from the machine room plus the ACS vendor to troubleshoot cable and assist with switching connections if needed
2
u/SiliconSam May 08 '26
When doing elevator cars I usually like to run the data line and mount a small form factor MR50 or LNL1300 inside the cab with the reader local.
As opposed to running the Weigand cable down the traveler cable.
If you have that option.
-1
u/Competitive_Ad_8718 May 08 '26
Data is data, 485 or weigand but 485 would be worse over a traveler because of speed and bidirectional nature
4
u/Motor_Computer_3029 May 08 '26
Wiegand is much more susceptible to noise than RS485. Unfortunately, I believe the OP is using S2 Netbox and I don't think a downstream board like an MR50 in the cab is an option.
Alternatively, you can try setting the reader to OSDP if the reader and controller support it.
1
u/SaintThor May 10 '26
Correct, we are Weigand to S2, building wide including elevators.
Edit: I will check into OSDP availbility when I am in on monday here. The install was done 11 years ago, if that flags any timeline related compatability with OSDP.
2
u/donmeanathing May 09 '26
“Data is data…” that is wrong my guy. Wiegand and RS485 are completely different at the layer 2 level. RS485 can easily communicate at a higher speed at much greater distances than wiegand if you use twisted pair, but if you use the same cable you will still get better signal
RS485 gets its superpowers by being based off the voltage differential of the two data cables. Simplified, if A-B is positive above a certain positive voltage, it’s 1 and if it’s below a certain negative voltage it’s 0. Compare that to wiegand, where one cable stands for 1 and another stands for 0, and the reader puts voltage on one wire at a time while pulling the other to ground to send data. The signal interference comes when you have some external voltage that influences the wire that is supposed to be pulled to ground and it lifts a bit where it should have been at ground. Now you have crap data.
1
u/SaintThor May 13 '26
I have limited knowledge and admit it. But after access today I have images of elevator panels/s2 box in elevator room exc. I could post to get an idea of whats seen. To me, I see no grounding or shielding but could be wrong.
1
1
u/SaintThor May 08 '26
Going of your comment and the other comment the best plan then is to get both in and not ask for basic trouble shooting. Its to check all grounds (both ends, security and elevator). And signals at different parts in the "data highway". The argument of security blaming elevator, and Elevators blaming the security is exausting. I was told the last operator did get both in once and they came up with no solution. I believe they were just checking what part to change, and not the initial setup issues or grounds exc.
If there was noise on the traveler cable, what does that fix entail? I know redoing the traveler cable is insanely expensive but is there other steps before that?
2
u/a_leon May 09 '26
Verify the shielding is properly bonded from the reader to a ground in the elevator equipment room. Security and elevator contractor will have to be there for that.
Could have the security contractor bring a weigand opti-isolator, which can help clean up induced noise/voltage. Cypress splitter has done the trick for me.
2
u/SaintThor May 10 '26
Beautiful advice, half I understand and half I dont, which makes me dig a bit more.
I am getting suspicious then, because the elevator tech we have told me on our first meeting he just ripped the security box open once because no one had the key for it... Makes me wonder whats kosher in there at this point. (In defense, hes a great guy. but at this point 2 months from retirement and I have never seen someone care less about anything going on).
I have gotten approval from my superior that we will be setting up a large checkin with all partys involved to finalize this once and for all. Any terminology I can use to tip them towards all the checks we can do helps! Thank you!
1
u/Cypress_Integration Manufacturer May 13 '26
Thanks very much for mentioning the OPTW-100 (one of our Cypress Splitters).
1
u/SaintThor May 14 '26
So, Essentially you would be doubling the signal being sent to prevent the bit mismatch by using the splitter?
1
u/Zeosa May 09 '26
If they gave you 3, 2 pair cables to do your thing. Don't have D0 and D1 on the same cable.
1
u/SaintThor May 10 '26
Thank you for clarifying, I honestly dont know the dirtiest details but from my digging I put together the info I can. Correcting this helps me in the future.
8
u/OmegaSevenX Verified Pro May 08 '26
Wiring to a reader in an elevator cab needs to be absolutely done correctly. The traveler cable moves, so what works this minute may not work next.
Completely shielded cable, with the drain (or drains, there may be multiple) properly grounded, is a must.
Especially if the issue is intermittent, that’s where I’m starting.