vze2jshn

After driving for a few hours on the highway I noticed a steady hum from the area of the central fuse panel on my '78. It sounds like an amplifier with no input to amplify. I was on the road and was unable to access the fuse panel. The sound continues with radio off and if I fiddle with seat belts and will only go away when the ignition is turned off and does not return immediately after starting the car again. Hopefully the next time it happens I'll be able to leave the car running, access the fuse panel and determine the source. I have Lo Jack and maybe that is the source. Until then I am wondering if anyone has experienced this and determined the source. Thanks for any ideas.

rnixon

Could it be the fan motor?

rbrtmchl

Could it be the O2 sensor counter? In this thread the description is a steady clicking noise. Might be?

https://rennlist.com/forums/928-foru...ble-noise.html

Wisconsin Joe

Could be a relay on the way out.

They have a "failure mode" where they buzz or hum as they fail.

Not super common (simply stopping working is more typical), but it happens.

Dr. Gonzo

Hello
could be the interior temp sensor fan.
Cheers.

vze2jshn

Thanks, I'll check for it.

vze2jshn

1978 no O2 sensor or fan temp sensor

vze2jshn

Thanks, I'll have to check with engine running next time I hear it. A relay may warm up and start humming.