: Weird thump from engine bay



psuscott0483
11-09-12, 11:28 AM
it has gotten much colder recently in my area so i dont know if that takes into affect what i am noticing but i have the temp set to auto climate control 70*F, every 30-40 seconds almost on cue theres a noticeable thump from the front (possibly passenger) side in the dash or engine bay. it can be felt and heard mostly while stopped but also while pulling out. while at cruising speed i do not notice with all the road noise, etc. any ideas what this could be or should i just take it to the dealor? i have a feeling this is one of those hard to explain things that the dealor will call and tell me they found nothing wrong. thanks!

48Dodge
11-09-12, 01:22 PM
AC compressor clutch?

psuscott0483
11-09-12, 01:39 PM
well that is an interesting thought i think you might be onto something. do you think the a/c compressor would run if it is 30 degrees outside and i have the heat on? the noise does not occur if i turn off the snowflake button!

jlawsonz
11-09-12, 01:58 PM
Yes, it does engage.

Why? You ask.
It's a simple answer... Ever seen people trying to clear their fogged window with whatever was available? Dirty shirts, socks and rags come to mind. The fog happens because of the abrupt change in humidity and temp on the inside. The AC work as a dehumidifier even if warm air is coming out, it's warm dehumidifier air.

I used to turn on the AC with the setting on heat in my old 1973 LTD back in the day and never had fogging issues and was always toasty.

psuscott0483
11-09-12, 02:01 PM
good to know, i will have them check the a/c clutch. thank you both!

Aerohokie
11-18-12, 06:22 PM
I had this problem too. A dealer told me it was compressor lugging caused by the oil and charge settling into the compressor due to how the lines are run. They serviced the ac and moved a line and I haven't had the issue again.

Cadillac Cust Svc
11-19-12, 03:44 PM
I'm glad to see you've found the forum feedback helpful so far, psuscott0483! If you would like me to follow up with your dealer at any point or investigate concerns further for you, please email me at Katie_Lucille@gmexpert.com!

Best,

Katie
Cadillac Customer Service

hannity
11-19-12, 04:33 PM
Sometimes compressors do make noises when the temperature changes. It probably is that.

SouthernCaddy
11-20-12, 09:32 AM
It is the door inside the heater box closing. It happens to alot of trucks. Nothing wrong with it, it just makes a noise when it closes. It is not the A/C compressor. It is the temp control door opening and closing.

48Dodge
11-20-12, 10:05 AM
It is the door inside the heater box closing. It happens to alot of trucks. Nothing wrong with it, it just makes a noise when it closes. It is not the A/C compressor. It is the temp control door opening and closing.

I've heard that before but it sounds more like a light tap to me. Could be right though.

Aerohokie
11-21-12, 07:33 PM
The thunk from the ac lugging on my ESV sounded like someone dropped an alternator from 3 feet off the floor. It scared you

SouthernCaddy
11-23-12, 03:23 PM
I heard my door close the other day...it made a thunk and I was sitting in the passenger seat. My wife said "what was that" I said the temp door closing. drive on....hope you find out what it is. If you do let us know so we will have that info.

thanks
SC