AC temp differences front/rear

[moda_way]

Originally Posted by N_Jay

But once you need it serviced it will be too late to know whether it was a slow failure or a sudden one.

Yeah, I agree. That's why I plan on getting that new filter (Acura P/N that does cross-over to Honda, but not sure which model) and replacing since obviously you are going to have to have an empty system of coolant to remove it. I'll snap some photos next week b/c it will probably be of interest to both this and the TSX forum as to what it looks like after 103k miles, albeit used on a fairly limited basis. The tech who is going to do the job asked, "How many miles?" When I told him, he said, "Be careful. That thing could go at any moment." Makes me question if I should do anything at all; remember, "fix that which is only broken."

I had to laugh because I was reading through one of my gun supply magazines and saw a desiccant filter mentioned. I've gone how many years now and not used desiccant filter and it shows up a handful of times in a couple of random places.

[N_Jay]

Find a good shop that has a machine that exactly weights the refrigerant and oil extracted, so you can refill the system with the precise amount of oil.

Let us know what the ""filter" looks like on a high mileage, but not yet failed AC system.

[hkellogg]

my guess would be is that the blend door is not closing, this is the door that closes off air flow to the heater core. As coolant is always flowing through the heater core this would definitely make for a temperature difference if the cold air is mixing with the cold air from the heater core area. I had an issue similar in my GMC jimmy had to replace the blend door motor

[theirishscion]

Originally Posted by darkdeacon

Two questions:

1. Any idea what could be causing the temp differences and how it might be remedied?

2. Could these AC problems be a result of the timing belt work that was done? It seems an odd coincidence as I wasn't having any problems before.

Thanks in advance for any help you can provide.

I can't really say whether the timing belt replacement has anything to do with it, but I have a theory as to why you are getting different temperatures between the front and the back. As N_Jay pointed out above in the thread, there are two separate evaporators, one front and one back. Both will have separate capillaries/orifices/whatever they're called in this country. That's the very thin opening the liquid refrigerant passes through just before it expands and cools in the evaporator. By their nature, these orifices are very small and susceptible to clogging up with crap, the sort of crap you might easily get thrown into the system by a failed compressor. My suspicion is that the shop that repaired the compressor didn't get all the crap out of the system and that your front evaporator has it's orifice somewhat clogged. The blend door idea would make more sense if it hadn't happened so close to the replacement of the compressor.

I'd love to hear what you find out when you get it fixed.

[hkellogg]

Originally Posted by theirishscion

I can't really say whether the timing belt replacement has anything to do with it, but I have a theory as to why you are getting different temperatures between the front and the back. As N_Jay pointed out above in the thread, there are two separate evaporators, one front and one back. Both will have separate capillaries/orifices/whatever they're called in this country. That's the very thin opening the liquid refrigerant passes through just before it expands and cools in the evaporator. By their nature, these orifices are very small and susceptible to clogging up with crap, the sort of crap you might easily get thrown into the system by a failed compressor. My suspicion is that the shop that repaired the compressor didn't get all the crap out of the system and that your front evaporator has it's orifice somewhat clogged. The blend door idea would make more sense if it hadn't happened so close to the replacement of the compressor.

I'd love to hear what you find out when you get it fixed.

ac systems have things called orifice tubes or expansion valves if any blockage were to occur he would not be getting cooling at all. I am almost positive it has to to do with the blend door and or HVAC controls. I've never heard of a timing belt issue causing any of this btw. I do AC work on the side for the past 4 years and can say ac is a totally closed loop system and its not affected by anything other than itself primarily.

[darkdeacon]

Thanks again for the help.

I thought for a second today that the problem had miraculously cured itself. It is only in the mid 70's today and the vehicle seemed to cool down nicely. However, sticking a thermometer into the vents still showed a difference... 55 in front and 41 in rear.

My mechanic is betting on the blend door. I guess I am skeptical that this problem wouldn't somehow be related to the new compressor work....Who knows, maybe it has been a problem for a while, but not noticable without an assist from the Carolina heat and humidity. Any idea on cost involved in fixing a blend door??

Just for my own education/curiosity, maybe you can help me understand the system a bit better. In the attached jpeg, the ice cold cooling pipe splits into two... the top is very cold, but the other is only slightly cool. Why?

Will be taking it in next week. I'll post an update when the problem is solved.

Thanks again.

[N_Jay]

I am putting more on something plugging the front expansion valve/orifice or evaporator based on that.

[hkellogg]

Originally Posted by darkdeacon

Thanks again for the help.

I thought for a second today that the problem had miraculously cured itself. It is only in the mid 70's today and the vehicle seemed to cool down nicely. However, sticking a thermometer into the vents still showed a difference... 55 in front and 41 in rear.

My mechanic is betting on the blend door. I guess I am skeptical that this problem wouldn't somehow be related to the new compressor work....Who knows, maybe it has been a problem for a while, but not noticable without an assist from the Carolina heat and humidity. Any idea on cost involved in fixing a blend door??

Just for my own education/curiosity, maybe you can help me understand the system a bit better. In the attached jpeg, the ice cold cooling pipe splits into two... the top is very cold, but the other is only slightly cool. Why?

Will be taking it in next week. I'll post an update when the problem is solved.

Thanks again.

That picture helps a lot.. it looks like the low pressure side line goes into a expansion valve and splits off going into the evaporator core in the dash and the core into the rear console. You might have a small blockage on the side that goes into the dash evaporator...you should be able to tell if there is a blockage by checking the pressures with a vacuum pump and gauge set

[theirishscion]

Originally Posted by darkdeacon

Just for my own education/curiosity, maybe you can help me understand the system a bit better. In the attached jpeg, the ice cold cooling pipe splits into two... the top is very cold, but the other is only slightly cool. Why?

Those two fat pipes are the refrigerant return lines from the evaporators in the cab. The skinny line underneath them (with the black cap on the fitting and the pressure sensor with wires coming out of it) is the high-pressure liquid refrigerant line, taking the 'loaded' refrigerant to the two evaporators. The orifices that I mentioned in my previous posts will be much closer to the evaporators that they feed.

Unfortunately, return pipe temperature only tells part of the story. Without knowing which pipe comes from which evaporator, there's now way of knowing whether the warm one is a blocked front evaporator orifice and the cold one is the working back evaporator, or the other way around, the warm one is the one coming from a working evaporator in the rear that is having all the cabin heat transferred to it and the cold one is coming from the front which has a stuck blend door and isn't getting any cabin heat transferred to it at all.

However, if I were a betting man, I'd stick to my original diagnosis. I'd give 5 to 1 that it's a blocked orifice of some sort at the front. Unfortunately, that's likely to be the more expensive diagnosis as well. Hopefully since you had the repair done by a national chain, you can bully them into making right for you. My guess is that they didn't successfully flush all the crap out of the system. They may not have realized (or cared) that there are two evaporators in the Pilot, which I imagine complicates the flushing process (one can be clear and make the whole system look clear while the other remains blocked, sort of thing)

Mark you, I'm anything but an AC tech, hell I grew up in a country where there was no AC. However, I did have to fix the AC in my old Ford about 6 months ago, before I bought the Pilot , so I've recently read up on the topic.

[N_Jay]

I think it is quite likely that the line running through the fire wall right behind the glove compartment is the front.

[theirishscion]

Originally Posted by N_Jay

I think it is quite likely that the line running through the fire wall right behind the glove compartment is the front.

Ooh, you're right, I'm blind, I didn't spot the flex hose in the photo, I thought they both went through the firewall. So I'm officially blaming this on looking at the photo on my little iPhone screen

With that in mind, I'm upping odds of a refrigerant path blockage to 25 to 1

Heh.
Cough.

While I'm looking at it on a decent screen, it also looks like the high side line splits into 2 at the same junction that contains the pressure switch, which is promising, I wonder if there's an externally accessible orifice somewhere nearby that would be nice and cheap to fix.

[N_Jay]

Pull the compressor and back flush the system.

[theirishscion]

Any update on what it was?

[darkdeacon]

Thank you for your help.

The technician on my latest visit was able to rule out the blend door. He believes that I need a new expansion valve and evaporator core ($587).

It wasn't an overly warm day when I took it in.... it tested out as only 4 degree difference front/rear (62/58).

I did not have the work done yet due to cost/time and the fact that technically the vehicle does cool down and stay relatively comfortable... though not likely on a really hot day.

In the meantime I have wasted much time talking to the NAPA "Peace of Mind" waranty representative. The warranty only covers the compressor/dryer. I contend that the original guy should have flushed the system and that his failure to do so has led to a blockage of some sort.

When I spoke with the original guy, he said that because only the compressor clutch had gone bad, that there was no reason to believe the system was contaminated and therefore no need to back flush. Is that standard procedure?

Anyway, until I have the system opened up again, there is no way to know if there is metal from the bad compressor in it and therefore no way to get relief from the warranty.

Right now it appears that I have paid about $1250 for an air conditioner that sort of works. My guess is that the blockage will get worse and I will need to have it taken care of. Is it likely that whatever is causing the blockage will eventually lead to failure of the compressor? With my recent luck, I expect that to happen minutes after the 12mo/12000 mile "warranty" expires.

Again, thanks for everyone's help. Info from your posts have greatly helped me to speak semi-intelligently to mechanics and warranty reps.