door locking at certain speed

I have seen these on factory alarm systems and also my fiance's aftermarket alarm has it (dont know how since its the same alarm as I have). Anyways, her doors lock when the car gets to 25mph BUT only when you give as hard acceleration. Does anyone know how this is done with factory alarm systems?

The OEM module recieves VSS, when it gets to a certain speed, it locks.   Never have seen an aftermarket alarm that does speed sensitive locks. Ever. I would hazard a guess that your fiance's vehicle has this as a feature already.....Wherever I go, that is where I end up......

Hmmm My 2001 chevy malibu does it at like 5 mph. often wondered how it did it myself...lol good info here thanks.

I've seen aftermarket speed controlled door locking systems - I'm sure they work the same as the OEM - through the VSS signal.Kevin Pierson

There are aftermarket remote starters that have RPM sensitive locking. Since they are hooked up to a tach wire already they just wait until the RPM are a certain point above idle and then they lock the doors. The reason your gf's car has to accelerate hard before locking the doors is because accelerating slowly doesn't get the RPM's to a high enough point before shifting. Compustar Pro units offer this feature, as well as older Clifford and Avital product (before they were acquired by DEI). I had an Avital 6500 that had it.

The alarm she has is a scytek 5100 RS and also has aftermarket door locks. She bought the car that way so I dont know how exactly they were wired up. The way her alarm is programed is to have ignition door locking and unlocking. When the car is turned off, the doors unlock like they are supposed to. When the car is started, the doors dont lock. You can be driving for an hour before the doors will lock. But I have been borrowing her car since tuesday since my car is it the garage and I take notice that if I accelerate up to 25mph, the doors will unlock, but if I happen to coast up to 25mph, they wont lock all the time. Its just weird. Is there a way to run a wire off of the VSS to a relay. The relay wont get engergized unless the VSS sends out the certain voltage, which in turn energizes the relay to lock the doors?

Shoot. Now I don't actually recall if the car did this before we had the keyless entry/alarm installed. I didn't install it...was shop done. Wrongly at first...LOL...went to drive away with it after paying and my alarm starts going off in their lot. Much to my displeasure I must say...lol. They disabled it and fixed it the next day. HMMM. puzzling indeed. I'm thinking about replacing this system with a 2 way for my wife though. Soon as I can afford to. Gotta keep up with the times. Besides she has to carry 2 fobs on the keys, 1 for alarm and 1 for starter, but that's been iffy lately. Replaced battery and seems fine for now tho'.

i can confirm the scytek does have RPM door lock sensing. If the unit detects anything from 3500 - 4000 rpm, it will pulse to lock the doors. Its rare to find this feature on units but most cars on the market today will lock once its put into any gear besides Neutral or Park eg Toyota Camry