'88 Prelude AC Clutch/Compressor Noise

The 88 Honda prelude used an A/C controller module that relied on several inputs to control various relays involved in Compressor clutch and fan operation. The symptoms you described would probably be due to problems in the controller or it's inputs, or maybe even the compressor relay. This is a fairly complicated electrical A/C control system and would normally require diagnosis by someone very familiar with the system, or at least the use of a very good repair manual and wiring diagram along with pretty good electrical diagnostic skills. I would have to recommend letting a qualified repair shop handle this one unless you don't mind replacing a lot of good components on a trial basis. My best GUESS would be that the control module is malfunctioning, and you still need to find out where the original loss of refrigerant occurred (although that may have occurred gradually and normally over the past 18 years). Good luck.

LET'S KEEP IT SIMPLE! It could be the clutch being rapidly cycled electrically or it could be a mechanical noise from the compressor. Fortunately it is very easy to take this first basic diagnostic step. A length of wire with an aligator clip on each will determine which it is -- no researching of wiring diagrams or anything hi-tech at all. Hot wire the compressor clutch directly to the battery and see if the noise is still there. If so, you would be advised to take a good look at the clutch hub -- these often come apart. Some compressors are noisy when badly undercharged and will actually get quieter with a full charge. Its worth a try. Do NOT try to get rid of the noise by blindly adding more and more oil to the system. If the clutch is being rapidly cycled electrically go ahead and charge the system properly and see if it persists. If so, then electronic diagnosis WILL be required. But before speculating about modules etc. DO THE SIMPLE AND OBVIOUS!!

Don

Good idea Don, I often forget to mention some of those obvious easy checks that could separate the cats from the dogs. I need to work on that. I guess the part about it only happening at idle made me think no way it could be the clutch or compressor itself, and I have run into the same situation on some of those modules, but of course, it can't hurt to check out the compressor anyway. Have you ever experienced a noisy compressor or clutch chattering only at idle that was not electrical. That's a new one for me. Thanks for taking up my slack. Sure would like to know what this one turns out to be.

Often -- when the clutch hub damper springs are broken, or, as in Nippendenso, the rubber dampening material is starting to tear.

On some compressors the reed valves make a lot of noise until the system is fully charged.

Anyway, a 2 foot length of wire will tell if the problem lies in the compressor itself or elsewhere.

Don

Thanks to both of you! I had the same thoughts, but for me they were wild guesses without supporting info from you guys.

The sound is a little bit "reedy" to my untrained ear. I have not inspected the clutch closely because of it's location. I'll pull the bottom engine compartment cover and take a closer look, and barring any obvious problems, I'll finish the charge and see if the noise stops.

Tom

By all means charge it fully. If the noise persists check it out with the clutch hot-wired direct to the battery and let us know.

Don

Well, it's charged and cooling nicely. The noise is still there at idle only, and it's intermittent at that.

According to the specs from the Honda dealer, it is now fully charged (2.25 lbs.), but it "acts" like it's still a little bit low on refridgerant. That is, the vent air temp rises considerably when idling (but that could be because the clicking clutch is not engaged full-time). Also, I can still see a very few bubbles in the sight glass. This is the first system I've repaired that has a sight glass, so I'm not sure what to look for.

I was tempted to add a little more refridgerant, but decided not to since the poundage is correct. If there is a major leak, I'll know it in a few days.

By the way, the original leak was almost certainly due to a loose Schrader valve. I replaced that before evacuating and as I mentioned earlier, the vacuum appeared to be holding.

By the way Don, nice website. I'm impressed that you publish your parts markup. I wish you were in Dallas!!!! I do my own (and my in-law's!!!) repairs for the most part, but I'm also pretty good at recognizing when a job is over my head and I like to have a relationship with an honest shop. I have a great transmission shop up here, and a great muffler & alignment shop, but no general repair shop that I trust.

Tom