Alarm going off on some mornings - already replaced hood sensor and IMS

randywei · #1 07-07-2021, 10:41 AM

I tried to monitor the sun and how it hit roof area near where the IMS is, but it looks like the car is actually in the sun for a good amount of time before the alarm triggers (when it triggers, since it doesn't trigger every morning).

I'm wondering if maybe some connection to the IMS is loose and when it gets cold enough, metal contracts so the connection becomes an open. Then when the temperature warms up (i.e. via the sun), the metal will expand and make a connection again and that trips the IMS.

andrewwynn · #2 07-07-2021, 11:06 AM

Quote:

Originally Posted by randywei

I tried to monitor the sun and how it hit roof area near where the IMS is, but it looks like the car is actually in the sun for a good amount of time before the alarm triggers (when it triggers, since it doesn't trigger every morning).

I'm wondering if maybe some connection to the IMS is loose and when it gets cold enough, metal contracts so the connection becomes an open. Then when the temperature warms up (i.e. via the sun), the metal will expand and make a connection again and that trips the IMS.

My impression is the sensor is sensing something not a connect/disconnect. I think you'd get a code for the device going offline.

I'm thinking something is heating unevenly and causing something to either bind and release like described above or dimple like an old timey oil can. (like a door panel etc).

randywei · #3 07-07-2021, 11:12 AM

Thanks for your suggestions and insight, @andrewwynn . Once I get the car back from the shop (assuming they're able to replace the recently swapped out IMS for a new one, under warranty) I did want to run an experiment of parking the car inside the garage to see if that makes a difference. Perhaps I can setup a time lapse camera as well.

At first I thought it may have been a bug inside the car, but then I would've expected the alarm to go off at random times, not just on random mornings around the same time.

Then the recent time when the alarm triggered right before noon after I flipped the car's orientation 180 degrees really threw me off as that was the first time the alarm went off so "late" compared to its normal ~8:20-8:30am triggering.

I know I can workaround this issue by double locking, but I really want to get this fixed if I can...