expansion valve

[natsoundup]

I thought my level of ignorance was improving, but maybe not.

I took out the glove box of the 90 Q in search of the a/c expansion valve.

Does anyone know where it is..... and can you get to it and replace it?

I see the blower motor, but that's about it. Searched the threads with little luck.

Manual doesn't seem to help either.

[911/Q45]

The expansion valve is located in the cooling unit to the left of the blower as you sit in the passenger seat. There are good diagrams on HA-6 and HA-36 of my 1990 manual. It appears that you need to remove the intake unit and/or the cooling unit to access the expansion valve.

[natsoundup]

anyone know how to get to the expansion valve?

[Q451990]

Typically you have to pull the evaporator box and the valve comes out with it... why are you replacing it again? I don't think that's what's causing your clatter noise, unless it's blocked or something. If I remember correctly, they're pretty expensive (plus the refrigerant recharge and dryer) so I wouldn't just toss parts at it unless you know for sure that it's bad.

Heath

[natsoundup]

the compressor and drier were under warranty....

so I just replaced those parts and thought I would do the expansion valve ....I didn't do that last year.... it was a 60 dollar part from Joe.... so that cost wasn't the issue....

[maxnix]

If your system is clean and well maintained, the expansion valve should be fine. Do you have high and low side readings that are way out of specification? If not, then the expansion valve is most likely just fine. Usually it fails by getting clogged with gunk from not maitaining the integrity of the refrigerant and lubrication.

[natsoundup]

I tried to get to the expansion valve and can't figure out a way to get the black plastic box off....seems like every screw that could come off has.....

the low pressure side is reading high...... the refrigerant is correct in the system.... the car seems to be cooling decently.

[maxnix]

I am no AC expert, but I would doubt if your expansion valve has failed. Do you know if you have the correct charge? I would evacuate (for a few hours) and recharge (even with R-12) before I assumed the expansion valve is kaput.

[natsoundup]

it's cooling adequately....yesterday was a hot one....in the low 90's with high humidity...

I am going to get a thermometer and see what it is reading. I suspect part of the problem is a lot of 14 year old parts. Although the evaporator looked nice from what I could see.... a bit of dust, not much else...

[texasoil]

The low side pressure in the A/C system is a function of how much coolant the compressor is pumping. The expansion valve will go wide open to try and get the outlet pipe temperature down to the valve set point.

Before jumping to conclusions, carefully check inlet and outlet temps in the car, outside air temp, relative humidity, and then look in the service manual for expected high and low side pressures.

A plugged expansion valve will give poor cooling and low low side pressure. A dirty condensor or bad fan clutch will give you high high-side and high low-side pressures. A non-operating aux fan will also give high high-side pressures also.

A dirty evaporator will result in less than optimal interior cooling.A leaky compressor suction valve will give high low-side pressure and low high-side pressure.

When ambient temps get above about 90F, you have to have real accurrate temp readings for good diagnosis. 'About' 95F' is not good enough. 94.5F is. Same with relative humidity.

Down here in Houston, the A/C load from the humidity is often greater than that from the temp.

[natsoundup]

texasoil----

that was the best explanation of a/c issues I have seen yet.... you have pretty much confirmed that I don't have an expansion valve issue...

I will have to check the pressures again this weekend...it is in the 90's here... humidity is up a bit...but nothing like it gets in Houston.

evaporator is clean....it held pressure during the vacuum pull.... I could be an ounce short of oil...

I will have to check the fan clutch...but I don't think that is an issue...

of course a black Q sitting in the sun doesn't help either...

the manual doesn't show much variance in low side pressures regardless of temp.

Thanks...

[texasoil]

the Q45 A/C compressor is a variable displacement type that adjusts its capacity to keep the suction pressure near constant. That is why if it is off much--the compressor is faulty.

[natsoundup]

I was able to reduce the pressure to normal range by releasing some of the refrigerant into a towel. Seems to be fine now.

[maxnix]

Ack!! Hope the EPA isn't monitoring this board. You may get a knock on your door late at night.

Now how do you know what your charge is? At least it is working well.

[Q45tech]

Members will be surprised at the difference 0.1 pounds will make"0.1/2.4= 4%................you must insert the correct weight of R12 and oil............then monitor the high pressure under very specific temp humidity and rpm in shade after 10 minutes to zero in on the absolute coldest vent vs pressure reading.

I did some testing in 0.1 pound [1.5 ounce] R12 increments and amount of oil in 0.5 ounce increments.........I was able to find 2-3 F better than spec cooling under 95F conditions.

Not sure people would pay $400 [for AC fine tuning] spent all day the first time zeroing in on optimum. Each system will be a little different, why factory specs a R12 range 2.2-2.4 pounds.....exact amount interacts with the brand, type, and weight of oil.

If you get too much oil you have to spend 30 minutes vacuuming it out weighting and readding..........kind of mix and match with 9-12 possible combinations of the two components

New vs used worn compressor and in between adds 3 more variables.

Why factory gives a 4F cooling range under each condition.