Car repair question...

I’ve got a 2000 Civic that’s had a rasping in the right side of the dashboard (only when the AC/heating system was running) for quite a while (I’d heard it as far back as a few months, maybe up to 10-12, but it only really got noticeable when driving relatively recently). It was diagnosed as an evap system pressure valve failing.

What exactly will happen/has happened if the valve fails completely? I’m trying to figure out how urgent this repair is, since it seems it’ll cost quite a bit to replace. (Although given the time it needs with parts order, it might be best to do it now time-wise; I just want an outside opinion.)

Thanks in advance!

In auto repair nomenclature, “evap system” means the evaporative emissions control system, which deals with fuel vapor emissions. Offhand, I’m not aware of any vehicle that has an evap system component in/near the dashboard.

If you’re not positive of the terminology, it could be a whole different animal. The A/C system has an evaporator in the right side of the dash. I know “evap system” and “evaporator” sound similar, but they’re worlds apart. We really need to know accurately (and precisely if possible) just what you were told to give helpful advice.

Either way, to investigate the particulars of your vehicle, I need to know the particulars of your vehicle. :slight_smile:

CX, DX, EX, GX, HX, LX, Si?

Hatchback, coupe, sedan?

(Normally would need engine size in liters, but for these models the preceding info will specify that.)

If it’s the A/C Expansion Valve, when it fails completely, you will either lose all your A/C refrigerant, and your A/C won’t work, or your A/C just won’t work.

If it’s an evaporative-emissions control valve, if it fails, the check-engine light will come on and the car won’t run properly.

Enough of these cars have been crashed that the parts should be readily available in junkyards.

LX sedan.

And what I wrote in my OP was basically what I was told (or what I remembered being told). It’s a little tricky because the diagnosis was loose — they (the manager and the mechanic) only went as far as figuring out where the sound was coming from (by hearing it and removing the glove box to find its source). Then the mechanic told the manager what he thought was going on (which I overheard, but don’t fully remember). What I wrote in the OP above was what the manager in turn remembered of what the mechanic said.

So basically, I don’t know which of the valves specifically is failing, but neither do they. So they want the car for a couple of days to first find out, then order the specific part (that’s where the time thing comes in).

When you say a rasping noise, does it happen all the time? Does it stop if you turn the fan off?
From the description my fist thought is the fan is making the noise. It could have a loose or cracked cage, the motor is going bad, maybe something got inside and is rubbing on the fan.

The noise is directly connected to whether the AC is on or not.

So it doesn’t change if you change fan speeds or turn the fan off?

I’m relatively sure turning up or down the fan doesn’t do anything. As far as turning the fan off, how do you do that without turning off the entire AC/heating system? The manager tried turning it up and down, turning on and off recycling and the AC, but none of that did anything to the noise, IIRC.

Because of the possibility that the A/C evaporator is involved, and because the description of the noise suggests the blower (interior fan), we want to sort out whether it is just the blower or whether the A/C must be turned on. So, does it make noise when the blower is on with the system in heat mode and the A/C off?

all i got to say, that will be fun to get to in replacing …

i have a 99 honda, and it was interesting replacing the cabin filter … =)

To clarify, the blower can be running (for heat or ventilation) with the A/C itself turned off. I’m pretty sure your system has a separate A/C button to engage/disengage A/C. While the blower must also be turned on for the A/C to operate, the A/C does not need to be on for the blower to operate.

The A/C might be on even though the A/C isn’t selected. Most modern cars will run the A/C if the windshield defroster is on.

One test would be to remove the fuse for the A/C system. If the noise goes away, you’ve narrowed it down to the A/C. If the noise doesn’t go away, you’ve narrowed it down to something besides the A/C.

If the noise goes away with the fuse out, you could drive it like that but just be hot in the winter. My son-in-law has a 2002 Chevy with an A/C compressor problem and he pulled the A/C fuse. The cost of the repair is more that a Cavalier with 230K miles on it.

These seem to be at odds with this (bolding mine):

There’s a pushbutton switch to turn the A/C on and off. There’s a switch to turn the fan on and off. If the noise comes on when the blower is turned on with the A/C off, it’s in the blower. If the noise comes and goes with turning the A/C on and off, it’s in the A/C system.

The description of the noise suggests it’s in the blower. It’s odd, however, that it would not change with turning the blower speed up and down.

This is a bit tricky because there’s no part called a “pressure valve” in the A/C system. There’s a pressure switch under the hood. There’s an expansion valve under the right side of the dash. However, I don’t recall ever hearing a noise from either of these in 40 years of working on A/C systems.

It it’s in the blower, it’s not a big job to get in there and see whether the noise is due to debris or a faulty blower motor. If things get worse and the blower fails, you won’t have any fan assist for heat, defrost, vent, or A/C.

If it’s in the expansion valve, failure means no cooling from the A/C. This won’t affect the mechanical health of the vehicle. It will affect your comfort in hot weather.

I can’t see that this vehicle has any evaporative emissions components in the area mentioned, so let’s rule that out.

Well, I’m sure I’m not using certain terminology right — or at least, more loosely than I should.

Also, given that when I turn the air system off, the noise takes a minute to run down and stop, the fact that it didn’t SEEM to stop when certain buttons were pressed or unpressed MAY be misleading.

Maybe I should just take it back in, even if it’s gonna cost me $800 to fix, if only to be sure WHAT it is.

What you describe sounds like a suction throttling valve. It will give the affect you are describing but I don’t know if your model car is so equippped.

It is not. It has an expansion valve.

It’s weird… The evening after I decided to take my car in, I took it out for a drive of more than sufficient length for the noise to start up again, and again the next day.

Nothing. After what was I think months of this noise, nothing.

I canceled the appointment, figuring it’d be useless for them to try to find the problem when the noise isn’t going, especially since it sure SEEMS like the heat is working fine, but I don’t know what to think. Should I take it in anyway? Or just look out for any problems with the heating/cooling? Just as long as doing nothing won’t hurt the car itself, I’m down with whatever.

I wouldn’t do anything unless and until the noise returns.

I’d like to bump with a report, now that it’s been a couple of months and I feel more confident in my impressions: while the noise has not returned, I am fairly certain that my AC system is running much hotter than it should. IE, when it’s set to anything beyond one-quarter away from the coldest setting, it makes the car very very warm, and when it’s set to the coldest setting, it’s not as cold as I think it should be.

What’s likely to be the damage (car-wise and cost-wise)?

With the AC in the max coldest setting and the outside temp above 60°F, put a thermometer in the vent. The temp should go below 40°F pretty fast.

My son-in-law has a 2002 Chevy Cavalier which has an AC compressor going bad. It will cost much more than the car is worth. So he pulled the AC fuse and just drives it. He plans on buying a new car before the summer heat hits. This might be something for you to consider.

Why pull the fuse? The compressor is going bad and making a lot of racket. On modern cars if you turn on the windshield defroster, the AC also comes on to help dry the air.