AC Fixed - now another issue

I wrote in a couple of weeks ago about the compressor on my 93 L03 - the clutch was not engaging properly. I tested it - It would not turn any rotations, completely seized. I took it into the shop - had the compressor, accumulator, and orifice tube replaced - $880.00 Canadian with labour and taxes. It works great now - very cold , except after 4 days there is a humming sound when the ac is on. It is not coming from the compressor, rather it sounds like it is under the dash or right next to the fire wall. The more gas I give it the louder it becomes. Sitting in the car with the windows up it is fairly loud. When I pop the hood and listen it is hardly noticeable.

Any ideas what might be causing this noise?? Thanks in advance.

Could be the blower or a vaccuum leak.

Could be the blower or a vaccuum leak.

You know my 86 does this. Makes a noise at idle that is only audible from inside of the car. I have never figured it out. I don't care as long as it keeps me cool when it's 100*F.

duplicate.

I have been trying to trace where the noise is coming from; I took the molding off under the glove department and it is much louder. Again only when it is set on AC or defrost. The compressor itself is not making any irregular noises and the air is very cold. But when the rpm's increase the humming noise gets louder and louder. Would the blower actually cause this type of noise? How to I actually access the blower itself? Maybe if I am able to play around with it the noise will stop. Any suggestions? Thanks!

If the system has an expansion valve instead of an orifice tube (some still do) it may be the source of the sound.

Bowtie,

Can you explain why a TXV would cause more noise? I'm sure my 86 has an orifice tube.

A pilot pressure or thermostatic expansion valve will not necessarily cause noise, but it CAN cause noise if the valve action is not smooth. My guess is that a '93 has plain tube(s) but some larger cars and trucks still had an expansion valve well into the '90s, and may still.

It has an orifice tube, and it was replaced new with the compressor and accumulator. When you place your hand under the glove box (touching the blower lines coming in from the firewall) while pushing on the gas pedal it actually physically vibrates and hums. ?? Once you switch to regular heat the vibrating stops, but you can feel the air still travelling thru the lines.

Hmm.. So it's like the evaporator coil is vibrating then. I wonder if there is some kind of cushion in there that has worn out?

I have been playing around some more the noise (after I got a boost - I left the interior lights on Friday night working on it). I do not think the blower can be causing this loud humming/vibrating, as the noise goes away when the heater is turned on and the blower fan is on max. Only on ac and defrost; when the blower fan is off or on max- the noise level is the same, it only gets louder as the rpm's increase. Even with the kick plate back on under the glove department I can feel the vibration when I lay on hand on the plate.

Maybe this is just normal and I should get used to it? Although I did not notice this noise or vibration until after the new ac system was installed.

Same here 1993,

Once I replaced the compressor, etc, and converted to 134, I've had this noise in my 86. Everything still works and still cools so...

Same here 1993,

Once I replaced the compressor, etc, and converted to 134, I've had this noise in my 86. Everything still works and still cools so...

I finally got the AC on my car fixed today - stupid A/C selector switch broke. The only noise it makes is a rattling sound when the AC is on, but this has nothing to do with the AC itself. Stupid power steering pump. It's an annoying noise and it's next on the agenda!

Interesting. But I don't hear anything outside of the car. Inside I hear the noise... I guess I'll have to check that.