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After two failed attempts to fix AC, now repair shop says my PCM needs replacement

I own a 2007 Kia Sportage. This past year the AC started to decline. Recently, I brought the car to our local Kia dealership repair shop. They attempted to diagnose the problem. First they recharged the system and injected die. This did not remedy the problem. Next, they said that a part located under the dashboard needed to be replaced. After $1300 dollars the AC was working. I drove the car home but in the morning the battery was dead. I brought the car back to the repair shop and the next diagnoses was a bad relay switch. They said the part would take about a week to come in (free of cost). The new relay switch was installed but blew. Another diagnosis was required. A week and a half later the new diagnosis was a bad PCM that will cost us another $1200 (excluding labor costs). I tried to explain that the PCM was fine when I brought the car in, and perhaps their previous repairs caused the problem. Being a lay person I am not sure if they caused the damage or not. I am seeking the help of this discussion board for an answer.

The PCM sends a trigger signal to engage the AC compressor. If that signal is not received then the AC will not work. It could be a bad PCM. I’ve seen this problem several times over the years and it’s easy to check. If the signal is a ground on your vehicle then simply send your own signal to check it. AC shops do this all the time and so do mechanics who work on AC systems. The PCM could work fine for all other functions but still fail when it comes to signalling the AC compressor.

Thanks Missileman. I find it suspicious that the repair shop did not diagnose it originally, but when they replaced the part (wish I knew the name) with in the dashboard, the AC worked again, then they diagnosed a bad rely switch, which blew again when replaced. Now it’s the PCM. Just seems suspicious from a layman’s perspective.

Repair shops aren’t always able to get the diagnosis correct on the first try. They use the same technique physicians use: “If you hear hooves stomping, consider the source to be horses before considering zebras.” It’s quite possible given what you say the PCM is indeed faulty, and that was the cause of the original problem.

You might ask why not just diagnose it correctly the first time? That’s possible, but it might have taken $2000 of diagnostic time. And then you’d still have to replace the PCM.

BTW, most of the experts here wouldn’t recommend a dealership for a 9 year old vehicle when the AC isn’t working. Dealerships are trained and tooled up to focus on warranty work. However in your case, as the PCM seems to be involved, in the absence of a local inde shop that specializes in Kias, going to a dealership probably made sense.

My spydee sense is telling me there is real trouble here going by what you stated about this. It sounds to me that the shop is over their head working on this problem and that is costing you a lot of extra money. If the PCM really is now damaged I have to suspect that the shop caused the damage, you and I can’t prove it but I sure do suspect it. You do have a point though that the PCM was okay when you brought the car into the shop to be worked on. The PCM shouldn’t cause damage to things like a relay. They usually just make a ground connection internally to turn things like that on. Techs that don’t know what they are doing cause the kind of damage and high repair costs you describe here.You have already spent a large amount of money to have the problem fixed and things are getting worse, not better. I would be having a serious sit down with the service manager about this issue and want a good explanation of what is going on and how can they justify the amount of money this repair is costing you. I would tell him that if adding another 200 dollars isn’t enough to fix this problem then it is time to leave and look for a better shop.

When new parts blow out is usually because something else is causing an extra current load on the circuit. The tech should be checking the circuit out before adding the new part so it doesn’t get damaged. I could be way off here about the shop but the time it has taken to figure out the problems, the added bad parts, and high cost to you makes me say what I did. Keep us posted.

Thanks for your help GeorgeSanJose and Cougar. You have both given me something to think about. I will keep you posted.

I’m going to be of little or no help here so I can only add this.
It sounds like a misdiagnosis; or several of them.

The flip side of that is that problems like this are often not in black and white. There’s a lot of gray areas in modern vehicles with the plethora of electronics involved.

While it’s not meant as a defense of the people who are running you through this headache, I will say that sometimes (considering the complexity angle again…) that a shop may make an educated guess at the problem rather than go through step by step procedures which can lead to many hours of poking around.
In a nutshell, the cost of the educated guess could be less than the billable hours devoted to tracing every wire and component involved and which even then may not provide a definitive answer.

In the old days A/C electrical systems were so simple that a technician could track an issue down sans repair manuals and just by visually following what few wires there are. Compressor, relay, high and low side pressure switches, and that’s about it on the old stuff.
Now there’s enough wiring to rig an airliner, compressor modules, blower modules, and a dozen sensors all tied in with the PCM.

It could also be that the tech who was assigned your car may have little experience with A/C systems. Even if the guy is “factory trained” that may not mean much. It only means they attended a factory sponsored school and were either given a certificate for showing up or possibly passing a multiple choice test. I do not know how Kia handles that phase of their operation.

Thank you ok4450.

A/c started to decline. It worked but not well. They evac system and recharged. And it worked better? Or the same? Sounds like it did not work better. Or even close to spec. Since they continued to change other parts.

@Johnny1962, @ok4450 is a long-time dealer tech and is giving you a good look at life at the dealerships he worked for.

Hi Cavelli, you are correct. The evac and recharge did not correct the problem. Thank you.

Thank you, jtsanders.

To reiterate, I’m afraid I’m of no help as there are so many unknowns; system pressures before and after the repair, how the compressor is engaging, etc how any (if at all) diagnosis was done and so on but my gut feeling is that this is a comparatively simple problem made worse by some guessing. Expensive guessing at that…

Before wading into big bucks on a PCM I would suggest finding an independent shop that specializes in A/C repair and have them take a look at this.
That gut feeling tells me you could end up with a new PCM and the same old problem if this is allowed to continue at the dealer.

There are too many alleged problems involved in the A/C for me to seriously believe the system is suffering all of those; and the new relay being described as “blown” makes it sound even more suspect.
If they used that “blown” term to you then I have serious reservations about their competency.

I want to thank everyone for helping me in this matter. I have decided to go ahead with letting the Kia dealer shop replace the PCM. After consulting with a few local mechanics, their experience indicates that it would be difficult to put the dealer shop at fault. Plus the dealer may be better equipped to program the PCM.

Other shops may also not want to deal with this what seems to be turning into a hairball repair. I can only hope that replacing the PCM for the exorbitant more amount of money they want for this that it will end this tale of woe to your pocketbook. My spydee sense tells me that replacing the PCM isn’t going to end the tale. Hopefully that is wrong. If it were me I I would ask the service manager for a big cut in the extra costs. For a little more money you could replace the entire car.