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post #1 of 30 (permalink) Old 06-06-2012, 07:33 PM Thread Starter
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Replaced Compressor, Engages With No Charge

So I got my compressor replaced along with the drier, and flushed the lines and condenser and evap. core. Got everything back together and took it to a shop to have it recharged.

The problem is the compressor clutch is engaging with no freon in the system. Also, while the compressor is engaged, the fans are NOT running, which they should be as far as I understand.

The compressor would begin to lock up after only about half a lb. of refrigerant was put in, which was due to the fans not running according to the mechanic.

I am assuming I need a new pressure sensor, as the compressor engages with it plugged in and doesn't with it unplugged.

However, I don't think a problem with the sensor explains why the fans aren't kicking on along with the compressor.

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post #2 of 30 (permalink) Old 06-06-2012, 07:35 PM
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Sounds like it's time for a fuse check?
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post #3 of 30 (permalink) Old 06-06-2012, 10:17 PM
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What did they flush the system with? It might be the system has a lot of stuff accumulating in the, well, accumulator. Your three wire transducer/sensor on the high side line should, (If unplugged), prevent the compressor relay from engaging. A/C is controlled by the PCM so, if it is coming on when empty, you might have fuse issues as stated before or, some shorted together control circuit wires.
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post #4 of 30 (permalink) Old 06-07-2012, 01:45 AM Thread Starter
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I flushed the system with an A/C flush solvent until it ran clear.

I will definitely check the fuses. I guess I just figured any blown fuses would result in the compressor not even coming on, rather than defaulting to a powered state.

After thinking about it, I figure that the compressor starting to lock-up when being recharged could be due to it not cycling off, rather than not having the fans on, or possibly both.

Whatever the issue, it likely was the cause of the original compressor's demise.
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post #5 of 30 (permalink) Old 06-07-2012, 02:46 PM Thread Starter
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I verified that the compressor clutch relay seems to be working normally, clicks on and off when the A/C is turned on or off (and the compressor goes on or off).

Fuses all look good, at least A/C related ones, will see if I have a proper tester later to check for sure.

I removed the pressure transducer from the line and gas started escaping. From what I understand, that should not happen. The FSM says that some pressure built up in the fitting may come out, but this was more like several seconds of gas coming out. So I wonder if that check valve itself is the issue.
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post #6 of 30 (permalink) Old 06-07-2012, 02:48 PM
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I was talking about fuses for the fans...not the AC compressor.

I did look at the FSM wiring diagrams. It looks like the same feed is used for the fans and AC compressor. It's Fuse D in the PDC. So if the AC clutch is getting power then the fans are getting power. Do the fans work when the car comes up to operating temperature?

As far as the transducer, I don't have any experience with that. If there is a check valve it may very well be defective if you had a pressure release for several seconds after removing the transducer. Sounds like it's built into the discharge line? So replacement of the discharge line if it's defective?

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Last edited by Ronbo; 06-07-2012 at 03:05 PM.
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post #7 of 30 (permalink) Old 06-07-2012, 06:28 PM Thread Starter
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Yep, fans are getting power, they always come on when the engine gets hot enough.

After scouring through threads, it seems that others have had the bad check valve, which will release refrigerant when replacing the transducer. Although, right now, there is no pressure in the system and the compressor clutch will still engage, so I think the problem is apart from the fact that the check valve is bad.

At this point, looks like I'm going to replace the transducer, since it is involved with control of the compressor and fans. Seems the most likely culprit to me. The only thing is that from most of the posts I've read, it seems that when the transducer goes bad, it usually gets stuck in a state where the compressor will NOT engage. However, that doesn't mean they can't fail the way mine seems to have.

I was wondering, when the compressor engages for the defrost mode, do the fans kick on?

Also, if I replace the transducer and it stops the compressor from engaging as it should, how can I verify that it will kick the fans on when the compressor does engage? Would I be able to take out the compressor clutch relay and jump the contacts? Or just have it charged and see what happens?

Edit: Yep the valve is in the discharge (pretty sure) line, not sure if it can be changed out or not, and the sensor screws into the line, then the connector plugs into the sensor.

Last edited by 94Beater; 06-07-2012 at 06:31 PM. Reason: Edit: Yep the valve is in the discharge (pretty sure) line, not sure if it can be changed out or not. And the sensor just s
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post #8 of 30 (permalink) Old 06-07-2012, 07:10 PM Thread Starter
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Actually, on thinking on this some more, if the transducer's output is simply "on" or "off" (I realize it is a variable voltage, but in terms of its effect), then the sensor being the problem wouldn't really make sense, because the fans should be kicking on, so now I'm thinking that the compressor is being energized through some fault in the wiring.

Hmm, except if that was the case, turning the A/C button on or off wouldn't control the compressor would it?
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post #9 of 30 (permalink) Old 06-07-2012, 08:08 PM
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Kind of a dumb question but has your AC ever worked before? If not..that throws a wrench into the typical troubleshooting.
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post #10 of 30 (permalink) Old 06-07-2012, 08:43 PM
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The purpose of the transducer is to monitor the output pressure/temperature of the discharge line. since there is a correlation between refrigerant pressure and temperature, this device lets the PCM know when to switch on the fans based on line pressure. Also, the pressure is allowed only up to a limit and then the PCM instructs the compressor to shut down. As the fans run and the pressure drops, the PCM should get the message to switch off the fans and allow comressor engagement.

I remembered after my first post that there was a TSB regarding 1st gen connectors at the transducer. This was a replacement only fix as we had to cut the harness and solder a new connector on while at the same time replacing the transducer. I'd look real close at this connection as well.

Also, I have my doubts as to the fault of the schrader valve at the transducer. It's natural state with the transducer attached is open always so if it leaks with the transducer off then, so what? You aren't planning to charge the system with the thing unscrewed anyway so I wouldn't worry about it. Just the o-ring that is on the neck of the valve is all that's important once installed.

I will look up that TSB if I can. But, if this system is building pressure without a charge of 134-a, then what's the pressure from? I'd venture another visit to the accumulator full of flush.
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post #11 of 30 (permalink) Old 06-08-2012, 01:12 AM Thread Starter
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Ok, so it sounds like the transducers job is not as simple as turning the fans and compressor on and off simultaneously. Would you say it is true that they are controlled independently? If so, that makes me lean more towards the sensor again, because that could maybe be the only problem. But I thought the fans were supposed to run if the compressor was engaged, no?

My A/C did used to work great until eventually the belt started smoking and burned up, apparently due to compressor failure, or rather due to this electrical issue causing the compressor to run continuously until failure.

I really wish I had another transducer to swap in and test, I called multiple junkyards with no dice.

I see that there are now aftermarket transducers, one by 4 Seasons and one by Santech which are significantly cheaper than the OEM. Except for the fact that it is about 30 bucks for the sensor, then another 30 for the plastic connector..

I suppose there could be some flush in the accumulator, but that would be a separate issue I think as the compressor kicks on immediately with an empty system, don't see how there could be any pressure to kick the compressor on in the first place. The compressor did start locking up while recharging, but that I assume is because it was stuck engaged. Also, I blew compressed air through each component multiple times and then let sit for a bit before reinstallation, so there shouldn't be much residue left hopefully.

Oh, is there an O-ring on the original sensor or just the newer improved one? Because when I took the sensor off, I didn't see any O-ring unless it was stuck in the line. I sprayed the sensor out with brake cleaner and re-installed with the same result.
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post #12 of 30 (permalink) Old 06-08-2012, 05:23 PM Thread Starter
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Ok, I picked up a new transducer and connector from Autozone, they actually both come together for about $35. Now I have to solder the new pins on, then put them into the plastic connector. Any tips on how best to do that? There are solder holes in the small shaft where you put the wire into. The hole almost looks too small to really get solder through it though..

Also, the instructions just say to mark down where the wires go, but the new connector is a different style. I'm assuming the top two wires on the old connector go into the two pins that are very close on the new connector, then there is the bottom one?
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post #13 of 30 (permalink) Old 06-08-2012, 07:29 PM
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Quote:
Originally Posted by 94Beater View Post
Ok, I picked up a new transducer and connector from Autozone, they actually both come together for about $35. Now I have to solder the new pins on, then put them into the plastic connector. Any tips on how best to do that? There are solder holes in the small shaft where you put the wire into. The hole almost looks too small to really get solder through it though..

Also, the instructions just say to mark down where the wires go, but the new connector is a different style. I'm assuming the top two wires on the old connector go into the two pins that are very close on the new connector, then there is the bottom one?
A picture is, (At this moment), worth a thousand words!

Just be sure you get the terminals back in the original spots. I'll take a peek at the wiring diagram over the weekend.
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post #14 of 30 (permalink) Old 06-09-2012, 03:05 AM Thread Starter
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LOL I felt the same way as I typed out that post. Here we go..

For sure I want to figure which lead goes where before doing any soldering, just not sure how the old sensors contacts correspond to the new one, they are shaped differently.

Notice how the solder holes are not on the spot where they are shown in the drawing. I feel like if I put solder there, it is just going to form a clump that's going to prevent the thing from sliding into the connector.
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post #15 of 30 (permalink) Old 06-09-2012, 03:27 AM Thread Starter
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And here is a horrible side-by-side of the connector ends of the new and old sensors. I guess it is fairly obvious how it should go, but I don't really feel like taking any chances with it.
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