A/C problem, and more pinging - TCCoA Forums
 
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post #1 of 9 (permalink) Old 07-13-2003, 09:50 PM Thread Starter
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Angry A/C problem, and more pinging

I'm on my second T-Bird now. The first one had a problem where the A/C would switch from panel to defrost whenever the engine was under mild load in a high gear, such as accelerating away from a stop sign at a leisurely pace. I thought that it might be low vaccum, but I never noticed any other problems that would indicate a lean condition.

Now, my new Thunderbird does exactly the same thing, only a little but worse. The difference is, this one runs WAY hotter than the old one, and the engine pings between 3800 and 5000 RPM. Whereas the old car hardly ever got up to the "N" on the temperature gauge, this one easily pegs it out if the engine is run at high RPM for very long. Cruising down the highway, the temp guage is normally about an eighth inch past the M, on the hot side. What's going on here?

The car has about 80,000 miles on it, and it was owned my a 50-60 year old school teacher when I bought it. Is this something that can be fixed, or is it just messed up from being driven short distances by an old woman for most of it's life?
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post #2 of 9 (permalink) Old 07-14-2003, 11:14 AM Thread Starter
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Today's update:
I cleaned the mass air sensor (again), and the pinging problem seems to have disappeared. The A/C thing is still present, however. Is this a common problem with the MN12s, or is there deffinately something wrong? The temperature gauge got up past "NORM", but it never did start pinging.
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post #3 of 9 (permalink) Old 07-14-2003, 11:26 AM
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I think you should check for a vacuum leak.

I had an 85 TC that would do the same thing with the A/C and there was a check valve that was bad. As long as you have vacuum it would keep the A/C vent closed, but under load, it would let the vent "relax" which put the A/C to the defrost vents.

But I don't know about the 4.6L. Do you have climate control or standard Heating and A/C?

I'd still bet it's a vacuum leak somewhere. It might even be under the dash.

And a vacuum leak could add to a lean/running hot problem.

Just my .02 and Good luck.

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post #4 of 9 (permalink) Old 07-14-2003, 11:43 AM Thread Starter
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A vacuum problem is what I was thinking, but, I have no idea where to start. I looked at the sticker under the hood, and identified most of what was on it. Nothing there looked wrong, and I didn't hear any hissing. However, the A/C vacuum lines weren't on that sticker, so I have no idea where to begin with them. Everything under the hood looks good, but I didn't check things such as check valves. How do you go about tracing a problem like this? Thanks!
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post #5 of 9 (permalink) Old 07-14-2003, 01:16 PM
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You might contact some local shops and see if they have a "smoke" machine. It's a machine that puts some type of smoke into your intake system (with the car off) and it is very simple to find all the vacuum leaks. You just look for the smoke and follow the trail to the leak. Leaves no residue or anything. Awesome machine!

I've only seen it used a few times, but it found multiple leaks in about 5 minutes! I don't know for sure, but I'd bet the dealership (cough) probably uses them.

Do you by any chance have an erratic idle with the engine “hunting” at idle?

Vacuum leaks are tough to find!!

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post #6 of 9 (permalink) Old 07-14-2003, 01:21 PM Thread Starter
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Quote:
Originally posted by 94 Daily Driven 4.6L
You might contact some local shops and see if they have a "smoke" machine. It's a machine that puts some type of smoke into your intake system (with the car off) and it is very simple to find all the vacuum leaks. You just look for the smoke and follow the trail to the leak. Leaves no residue or anything. Awesome machine!

I've only seen it used a few times, but it found multiple leaks in about 5 minutes! I don't know for sure, but I'd bet the dealership (cough) probably uses them.

Do you by any chance have an erratic idle with the engine “hunting” at idle?

Vacuum leaks are tough to find!!
No, I havn't noticed any idle problems at all. Now that the pinging seems to have gone away, as far as the way the engine runs and has power, there is nothing noticably wrong with it until you look at the temp gauge or notice that the AC is blowing on the windshield instead of you!
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post #7 of 9 (permalink) Old 07-15-2003, 12:29 AM
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My A/C does that too. I added additional vacuum and checked all the vacuum system , even isolated the feed to the system. I am about to remove the climate control module and see if there is a leak in the switching. The vacuum gets rerouted with the selector switch. I noticed that if I run it in A/C mode and not MAX mode it does not start blowing out the defrost vents. Maybe the valve portion of the switch is not indexed right and has overlap issue.
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post #8 of 9 (permalink) Old 07-16-2003, 04:06 AM Thread Starter
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Quote:
Originally posted by RichardM
My A/C does that too. I added additional vacuum and checked all the vacuum system , even isolated the feed to the system. I am about to remove the climate control module and see if there is a leak in the switching. The vacuum gets rerouted with the selector switch. I noticed that if I run it in A/C mode and not MAX mode it does not start blowing out the defrost vents. Maybe the valve portion of the switch is not indexed right and has overlap issue.
Okay, here's another update. I found the check valve and tested it, and it seemed to be in good working order. I was sitting at a stop sign, and with the A/C on low I could just barely hear a hissing noise, almost as if it was just the fan making the noise. I pulled the control unit out of the dash, and the noise got much louder. Apparantly, the switch itself is leaking whenever the A/C is on Max. I switched it to normal A/C and the problem (and hissing noise) went away. So, where do you get a replacement valve?
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post #9 of 9 (permalink) Old 07-26-2003, 10:16 AM
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Well I took apart the control switch. It need to be controlled carefully, but here is what I found. There is a multilevel electrical switch with a gear at the rear that drives a labyrinth seal that guides vacuum out the tubing ports. I reindexed that thing a few times and reassembled the switch and I finally got it lined up where it works right. AC MAx has fully recirculated air now and opening the throttle does not affect it.
Prior to doing this I noticed that if I held the selector knob somewhere in the middle of each of the settings, I would hear the air directors changing, but the electrical function was not changing.

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