[DMCForum] Re: Clicking noise behind passenger seat when A/C on

["cruznmd" <racuti1@xxxxxxxxxxxx>]

The noise you are hearing is the fan relay.

Your A/C system likely needs a recharge and is experiencing low 
pressure. The system will continue to blow cold in this condition as 
long as there is enough pressure in the system but when it leaks 
enough so that the low pressure switch no longer engages, the 
compressor and fans will no longer engage and of course, the air will 
be warm.

Before you sweat the leak though, it could be as simple as a worn O-
ring. My system is 23 years old and was open to the air for quite 
sometime. Walt replaced some O-rings and high side hose? (short one) 
and my A/C has been cold ever since.

I have John Hervey's fan fix 2X2. The relays are audible but he has 
tied the cooling fan failure light to them so the light comes on when 
the fans run. That way I know how long the A/C system is running the 
fans, and hence the compressor. I just trimmed a piece of black 
electrical tape over the word "fail" on the warning light so it 
says "cooling fan".

I don't know what the ambient air temp is where you are, but you do 
realize that the cooler it is outside, the shorter the cycle time for 
the compressor right? The workshop manual has a chart of times, temps 
and pressures based on ambient air temp.

Lastly, the reason you don't notice this when you are idling is 
because the compressor isn't pumping as hard under low RPM's vs. when 
you're driving so the low pressure switch doesn't cut out as often.

I'm not the A/C god here. It would be a good idea to confer with Walt 
to make sure I'm not talking out of my tailpipe.

Rich A.
#5335

--- In DMCForum@xxxxxxxxxxxxxxx, "lakelanier20" <derek4567@xxxx> 
wrote:
> 
> Alright, here's another technical question for you guys....
> (On the last one, Walt was of great help and I fixed that issue 
> easily).
> 
> I've had my car for 3 1/2 months now, and just prior to getting it 
> the A/C system was serviced by DMCH, so I know everthing was ok 
with 
> it when I got the car. Starting about 2-3 weeks ago, whenever the 
A/C 
> is on, there is a constant (literally about every 5 seconds) 
clicking 
> noise coming from behind the passenger seat. I can't tell if the 
> cooling fans are turning on and off with the clicking noise because 
I 
> can't hear them while driving, but I do know that at night the 
> headlights dim slightly whenever the click occurs (not every five 
> seconds, I'd say more like every 20 to 30 seconds). The A/C still 
> blows ice cold as it did 3 months ago. Can anyone tell me if there 
is 
> a problem and how to go about fixing it? Could it be as simple as a 
> corroded or dirty contact somewhere? (crossing my fingers in hope)
> 
> Thanks a lot,
> -Derek L
> VIN 5302

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