Home » The Genius Way BMW Solved Frozen Door Locks

The Genius Way BMW Solved Frozen Door Locks

Bmw Heated Locks Ts2
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If you’ve ever relied on a car with manual door locks as daily transportation in a wintry climate, you know lock cylinders aren’t moisture-proof. Here in the north, we have plenty of experience with fiddling around with lock de-icer or heating up the key blade with a lighter in an attempt to thaw the lock cylinder. Little did many of us know, BMW already had this situation figured out, because the automaker used to offer heated door lock cylinders on most of its vehicles.

Heated locks were offered on many U.S.-spec E24 6-Series coupes, E28 5 Series sedans, E34 5 Series models, E32 7 Series models, E36 3 Series models, and Z3 sports cars, as well as less expensive models when bundled into winter option packages. The ingenious driver’s door lock cylinder heaters tapped into components already in use within the car to get owners into their BMWs in properly cold weather without any hassle.

Vidframe Min Top
Vidframe Min Bottom

So how did they work? Well, a microswitch on the door handle otherwise used to activate the dome light would instead activate the heating circuit when the door handle was lifted. From there, a time-delay relay managed current sent to a horseshoe-shaped heating element attached to the driver’s lock cylinder, which would warm up the cylinder. After a few seconds of lock-warming, the time-delay relay turned the heating element off to avoid the potential of a thermal event. Easy, peasy, lemon-squeezy. However, mid-way through the 1990s, BMW’s heated door lock cylinders started to disappear.

Bmw Heated Door Lock Diagram

See, remote keyless entry was becoming a big deal, and if the door locks can be popped electronically using radio waves, logic suggests that owners wouldn’t need to put their keys into actual lock cylinders. Thus, BMW’s heated door lock cylinders went away because customers stopped using them. I mean, think about it — if you have functioning remote entry, when was the last time you put your key in the door lock instead of just hitting a button?

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Bmw Heated Door Lock Harness

However, if you own a BMW that was available with a lock cylinder heater but didn’t come with it, retrofitting one might not be hard. The whole system uses minimal wiring, and some cars come pre-wired for it. For instance, 1990 and later E30 3 Series models should already have a wiring pigtail in the door for a lock cylinder heater. Some parts, such as certain time delay relays and sub-harnesses, are no longer available new, but spares pop up on eBay and BMW still stocks heating elements and microswitches for retrofitting and maintaining these systems.

Mind you, now that most BMWs fitted with heated door locks are genuine classics, they don’t see the same amount of winter driving they perhaps used to, making this feature more of a curiosity than a solution vintage BMW owners are in active need of. But who doesn’t like a curiosity? Sometimes it’s the little things that add whimsy to life, and if a heated door lock isn’t whimsical today, I don’t know what is.

(Photo credits: BMW, eBay, realoem)

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ADDvanced
ADDvanced
21 days ago

My 95 Audi S6 has these. Works the same way. Hold door handle up and it heats them up, IF it is below 32 deg. I don’t think BMW started this, since BMWs are generally RWD and useless in winter. I would put money on Audi being the one that pioneered this tech.

Col Lingus
Col Lingus
22 days ago

Actuators are usually a pita to change.
As such I tend to use my key 90% of the time.
Except for when I have two arm loads of crap.

Eric L
Eric L
23 days ago

I came across these when I was replacing the micro switch on my door handle on my E30. It is interesting how it all works. Once I replaced that micro switch my delayed theater lighting started working again in the car.

Danger Ranger
Danger Ranger
23 days ago

I wish both my winter cars had this feature. I don’t even lock the Ranger anymore because I have had to use a coat hanger to bypass the lock cylinder on a -30 windchill day. My locks haven’t frozen on the ZJ, but the driver side handle/button was frozen for 2 straight days, no opening from the outside!

EricTheViking
EricTheViking
23 days ago

“Here in the north, we have plenty of experience with fiddling around with lock de-icer or heating up the key blade with a lighter in an attempt to thaw the lock cylinder.”

Ah, nice childhood memories in Germany for me in the 1970s!

JasonP
JasonP
23 days ago

Audi had a similar system on the C3 5000 / 100. I think it came with the refresh in 1989.

Mr Sarcastic
Mr Sarcastic
23 days ago

I am confused, the only time I have had trouble with frozen door locks was in Vermont at 20 below 30 below with wind chill and my key fob remote couldn’t unlock the doors. Fortunately a drinking buddy with a 1978 Ford 150 gave me a ride home. Even when I returned at 10 below the locker wouldn’t budge. But of clearer mind I opened the rear cargo hatch that was key only climbed over the seats started the engine ran the heat and poof the electric stuff started working. The key didn’t work in the doors because such a good seal you couldn’t pull it open.

Totally not a robot
Totally not a robot
23 days ago

My previous car never treated me to the beauty of frozen door locks. Instead, the door handle snapped off so I just stopped using that door altogether!

Goblin
Goblin
23 days ago

Coming from this, and arriving to BMWs nowadays that not only have just one actual lock, but it’s also made of soft cheese and fails if its used on a regular basis for more than a few months. Oh, how the mighty have fallen.

Ben
Ben
23 days ago

I mean, think about it — if you have functioning remote entry, when was the last time you put your key in the door lock instead of just hitting a button?

It was a few years ago, but highly relevant to this article because I was out snowshoeing on a very cold day and my fob battery got so cold it quit working. I had to use the emergency key to get in. Luckily the lock had not frozen though.

UnseenCat
UnseenCat
24 days ago

Now we need a solution to the other Northern weather pattern — when the weather changes from rain, to freezing rain, to ice and snow. And then when you go to get in the car, the doors unlock just fine but pulling the handle results in nothing happening because the entire door is frozen to the seal thanks to a thin layer of ice and won’t budge without some tugging, cursing, and hope that it won’t pull the door seal out with it.

Or when the same kind of weather makes it so that the power window sticks in its track when you’re in a drive-thru, and have to open and slam the door several times to jar it free of the ice.

Actually, EV’s ought to have plenty of power on tap to run lightly heated door and window seals to eliminate the problem. which manufacturer will be the first?

Dest
Dest
23 days ago
Reply to  UnseenCat

I spray down my door seals every winter with some type of lubricant (whatever I have handy usually, I haven’t found one that works especially well/worse than others) and it helps a lot.

Mike Dris
Mike Dris
23 days ago
Reply to  Dest

I used to use silicon because my dad did. No idea where he got the idea as he is far from car guy.

Mr Sarcastic
Mr Sarcastic
23 days ago
Reply to  Mike Dris

White lithium grease.

ADDvanced
ADDvanced
21 days ago
Reply to  Dest

You want this:

https://amzn.to/3PKdtLU

Car Guy - RHM
Car Guy - RHM
24 days ago

Frozen latches has been a problem on some of the current generation of F150’s. On my 2018, the first winter it hit below freezing, once opened neither door would latch. First time in, Ford would lube the latches, second time, they tried some other fix which didn’t work, finally the third time in the replaced the entire latch assembly which took care of the issue. It was ridiculous, should have replaced them the first round knowing they had an issue. Not sure the exact problem, it looks like some batches of latches either were out of tolerance or made differently which subjected them to freezing. No problem since they were completely replaced. Otherwise I’d be searching for old BMW hardware, or better yet ditch it and get a GM, Dodge or Toyota.

pizzaman09
pizzaman09
24 days ago

I do daily drive my e36 M3 in the winter and have found this feature useful a handful of times. It’s awesome, lift the handle, wait like 5 seconds and the door lock unfreezes.

My e36 doesn’t have remote locks, so it has to be locked/unlocked with the key.

Industrial_design_guy
Industrial_design_guy
24 days ago

It’s okay though, I won’t be driving my E30 during the winter anyway!

AlterId
AlterId
24 days ago

I don’t remember the last time I saw even lightly frozen door locks. I remember a few times when there was a thin layer of ice on the door frame and maybe a little internal freezing as well, but that was probably some 30 or 40 years ago. Now, even without remote locks, climate change has eliminated that hazard in these parts.

Phantom Pedal Syndrome
Phantom Pedal Syndrome
24 days ago

Just stoop down and give that frozen lock cylinder a few hot breathed kisses.
It’s fine. Nobody is looking.

IRegertNothing, Esq.
IRegertNothing, Esq.
24 days ago

That’s absurd. You have to drop your pants and smush a butt cheek over the lock.

Crank Shaft
Crank Shaft
24 days ago

I just spray nice warm pee into mine. Works really well and smells fantastic later on those hot summer days.

Note that I do need to angle my body to right due to my stick pointing to the left.

Urban Runabout
Urban Runabout
23 days ago
Reply to  Crank Shaft

Works on jellyfish stings too.

Mr Sarcastic
Mr Sarcastic
23 days ago

No just lick the coldest part of the lock. It tastes like strawberry

Urban Runabout
Urban Runabout
24 days ago

Just lick it!
I triple-dog dare ya!

Last edited 24 days ago by Urban Runabout
Phantom Pedal Syndrome
Phantom Pedal Syndrome
23 days ago
Reply to  Urban Runabout

Thtuck! Thtuck! Thtuuuck!

MrLM002
MrLM002
24 days ago

While I’ve had stiff door locks before, never have I had one freeze, in spite of having been through many winters with my automobiles.

While we’re on this topic though I have a general hatred for traditional keys, they’re too damn flimsy, way too easy to bend, and still too easy to break. While they are easier to pick, I much prefer tubular locks (as well as other circular and spherical things in general).

Richard O
Richard O
24 days ago

I retrofitted the system to an ’89 325ix and it was easy. You need the heater element and the microswitch. Everything is plug and play. As a bonus, the microswitch for the heater is a better quality than the standard one. (Which, by the way, is probably broken.)
Heated side mirror glass is another easy upgrade. IIRC, you can use donor mirror glass from a 5er E28 or 7er E23. You simply have to tap into the existing power mirror wires.

Urban Runabout
Urban Runabout
24 days ago
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