[Sears]

Hello all, I've got a rather odd issue with my 968 that may be related to the malfunction of my HVAC system. Last year, my A/C worked just fine. This fall the heat began acting odd, as it would sometimes get hot very quickly. Now, it rarely ever gets hot no matter where I adjust the t-stat. And the A/C no longer cools (the compressor does still kick on).



Now for the odd part...there is this occasional very, very fast clicking sound that is coming from the passenger footwell. It is not very consistent, sometimes it clicks for 2 or 3 seconds as I back out of my garage in the mornings, other times it clicks after deceleration (for exapmple, after I've exited the highway and am sitting at a stop light). Anyone have an idea as to what this noise could be? Everything else on my car works as it should.



Thanks in advance for your thoughts/ideas.

Chris

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[Chris Vais]

If you are not getting any heat, it may be that the heater control valve is stuck in the closed position. As far as the AC is concerned, I had the ac on my 968 not produce cool air because of a loss of refrigeratnt. This can occur as the result of a refrigerant hose leak or a pump seal failure. The other time the A/C stopped working properly was as the result of a very dirt pollen/dust filter. It caused the A/C to cycle on and off rapidly that produced a clicking sound like a relay or switch opening/closing in rapid succession. If the filter is very clogged insufficient air passes over the A/C heat exchanger. When that happens the thermostate in the A/C sense that the air is cold enough a shuts of the compressor.

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[Sears]

Chris, thanks for the feedback. I should have added that the heater control valve is in working order (it is about 1 year old, replaced it as preventive maintenance). It is very well possible that the refrigerant is low and that I have a separate issue with the A/C. It just doesn't make much sense to me yet as to why the heat sometimes works and other times doesn't when the heater control valve opens and closes like clockwork.

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[DaveN]

There are actuators that drive little metal bars to control the air ducting under the dash. If either of these servos is failing it could be reaching it's limits and clicking as it slips a cog due to it not stopping when it should. One of these, the one that usually breaks (white plastic joiner) controls the heat - usually if the plastic joint breaks you get full on heat all the time.

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[Sears]

I checked those actuators (located in the driver's footwell) and they are in good shape, look like new. I think it's time to take it in to a shop unfortunately, not much more I can do.

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[Big Carl]

I have a similar issue with my car. I assumed it had to do with the thermostat, because when it happens I can turn my thermostat up or down a few degrees and it goes away. Interesting thought on the pollen filter, ill have to check that out...

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[Sears]

My clicking is very odd, happened a few times today, both after decel (sitting at a light). It is very quick and high pitched, not super loud though. It then stops, the clicking slowing slightly before stopping. The noise is so fast it is almost is a constant 'zip' sound.

No idea if it is related or not to my cooling/heating issue.



I've got a 92, so no pollen/dust filter to clog. I get plenty of air, that isn't my issue. Blower works fine.

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[tamathumper]

I'm curious to know if your climate control tube is still connected behind the dashboard and up inside the footwell. Sometimes the climate control relay(s) click incessantly on cold start, as mine did once or twice, but they haven't really done so since I reconnected that tube.

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[Sears]

Interesting, what is this climate control tube you are referencing? This clicking is certainly incessant to say the least. I have learned a bit more about it as I just had my a/c and heat fixed (had a vac leak which was causing flaps to remain closed but HCV to be wide open and seperately had a bad service port on the a/c that caused freon to leak out). A/C and heat work great now, save this clicking. The clicking only occurs when the a/c compressor is off though. Turning the a/c on immediately stops the clicking in it's tracks. If you could point me in the direction of this tube I'd really appreciate it.

Thanks,

Chris

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[tamathumper]

There's a little round "vent" on the dash, just to the right of your cigarette lighter. Behind it, there is a long, flexible rubber tube that travels forward and into the ductwork on the firewall.



From memory, it's 8" to 1' long, and about 1" in diameter.



You'll have to bend yourself into a bit of a pretzel shape to see it.

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[Sears]

Thanks. I assume I will need to pull the glove box to access? Or do I just need to get upside down in the footwell (which is oh so fun, but better than doing so in my old MG at least).

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[tamathumper]

Yes, I believe you'll have to remove the entire glovebox to really get any view of it or to have any chance to manipulate it.

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[Sears]

Ok, I've learned a bit more about where this clicking is coming from. It isn't related to the interior temperature sensor, that tube is hooked up appropriately, confirmed by removal of glove box, which was easy. The specific noise is coming from the pipes that feed the coolant to the heat exchanger (heater core) that is under the dash. The noise is right at the joint of the two in/out pipes that run parallel to one another. They are located on the right side of the console (or put differently, where your left leg goes if seated in the passenger seat (US car, LHD). I have noticed that these coolant pipes are hot all the time, though heat isn't coming out of the system. The clicking also stops as soon as I engage the A/C compressor. The A/C works great, I had that fixed shortly and the mechanic just never did anything about the clicking, brilliant. Any ideas folks?

Thanks,

Chris

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[DaveN]

It could be that the idler pulley on the A/C is a little out of spec and rubbing on the A/C housing. When you engage the A/C the electromagnet latches onto the compressor drive wheel, stops turning independently and therefore no ticking?

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[Sears]

Dave, I don't think that's it as the noise isn't under the hood, it's just in the cabin, right by the center console.

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[Sears]

So I'd like to resurrect this thread as I still am experiencing the clicking despite my mechanic's best efforts at diagnosing this, the problem still lingers. He replaced several of the HVAC components that are buried beneath the dash & glovebox (the small parts that are actually clicking) with some NOS parts he had in his shop. Thankfully, he didn't charge for that work. His best guess is that the HVAC head unit is malfunctioning and of course that is quite the expensive fix.

Now to the reason I'm bringing this topic back up: I just figured out that if I turn on the recirculate function, the clicking stops in its tracks. I figure this might narrow the possibilities of what is really wrong with my system. I'd note the clicking can be somewhat controlled by turning the thermostat to a warmer position. If the A/C is on, the clicking stops, same with the recirculate button being on regardless of the A/C. Any thoughts are welcome.

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[kwikt]

At the end of the tube behind the glove box is a turbine type fan which is your interior climate control temp sensor. You might check this to see if something is jammed in the fan fins. I used compressed air to blow mine out. Now I tried a different climate control unit once and it made a crazy clicking sound also. I changed the unit and the clicking stopped.

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[tamathumper]

I am waiting for a very cool morning to test mine again, as it happen(ed) most often on cold mornings when I backed out of the garage, and for about 2-3 miles of driving each time I hit a bump in the road. A rapid-fire round of clicking would ensue.



I removed the A/C relay, took the cover off it (very simple to do) and bent the spring just slightly (the little "O" on each end of it) to provide a bit more tension. I figure the spring was aged, and it was allowing the relay to slap back and forth when I hit a bump. I haven't had any clicking since I did that, or very little, and I'll report back if it helped in the long run. Just removing and reseating the relay may have helped as well...



I would note that my recirc function would not work when the clicking was going on, the little orange LED on the recirc button would go out while the clicking was happening.

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[Sears]

Tama, interesting that the recirc light would go out, my recirc light glows constantly and it completely stops the clicking. Driving me nuts.

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[tamathumper]

Might be two different causes - mine could be the relay, and yours could be a vacuum leak or the solenoid going bad. Or vice versa. Or something totally different. Or,...

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