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Solved AC issue, ongoing

Prefix for threads that contain problems that have been resolved, and there is an answer within the thread.

ThunderbirdSport

Well-Known Member
Joined
August 4, 2013
Messages
358
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Location
Thunderbird Heights
City, State
Missouri
Year, Model & Trim Level
2006 Eddie Bauer V8
Issue solved. Was the Cylinder Head Temp Sensor, under the intake, on the passenger side.

30 minutes to pull the TB and intake...30 seconds to replace the sensor. Love me some Ford engineering! ;)



My AC issue is still ongoing, in a nutshell, the engine overheats, ONLY when the air is on, and only at highway speed. Just cruising around 25-30, or idling, it stays frosty cold and the temp gauge stays normal.

If I'm out on the highway or anywhere around 45 or faster, the AC blows cold for about 5 minutes, then gets warmer as the temp gauge maxes out.

If I turn the AC off, it goes down to normal and stays there, until I switch the air back on.

I've put a shroud in (missing when I bought the Expl in March) new fan clutch, new T stat, new water pump, flushed radiator, all hoses, even flushed the coolant in the engine until clean water ran out.

Now, I did some reading on some links google kicked up...anyone ever hear of having the fan clutch programmed? That's what one link suggested, via a Ford dealer.

Another link said some stuff about a thermo bypass that's inside the transmission. No idea why this would make the engine overheat when the AC is on, however.
 



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Would the engine coolant temp sensor being bad cause this?

Anyone? Anyone out there?
 






I recall a similar issue with Ford Contours that was always traced to folks having removed the air-flow panels under the engine, which changes the air cooling at speed when the radiator fan is no longer the prime source of airflow. Have to checked to see if all the panels under the engine are in place, since yours was also missing a fan shroud?
 






Pretty sure everything is there, there's a sort of a small air dam, maybe 2, 3 inches "tall"....

I've had a few '88 Thunderbirds, the incoming cooling air mostly comes in under the bumper and is deflected up to the radiator, so I get what you;re saying. ;)

I've googled some pics, everything I've seen, mine looks like, so I'm thinking it's not the issue. Good tip though, I appreciate it! :)
 






I put a new CHT sensor in, didn't solve anything. Fan seems to run more like it ought to, though.

I'm at my wit's end with this damned thing.

Guess I'll be calling the ford dealer tomorrow and seeing when they can do a diagnostic scan and go from there. FML.
 






I'm perplexed. So I'm going to reach back into my mind and say forget the normal stuff - it's been done.
Have you replaced the idler pulleys for the belt? Reaching way back into the improbable maybe the bearings are so bad that they are locking at high RPMs with the additional load of the AC? Look for rubber residue on your pulleys?
Sorry man - that's all I've got.
 






Using the correct coolant? Pressure tested the cooling system? How about the rad cap? Blown out the back of the rad with compressed air? The condenser and rad collect a lot of road crap over time.
Can you monitor the temps with a scan tool? Not unusual for these trucks to run hot when under load with high ambient temps.
 






I think it's time to do some narrow-it-down testing. Does the car do this (a) everytime, or just intermittently; (b) at the same speed (within +/- mph) on the highway, or at a different speed each time; (c) if you can drive and approach that speed in (b) and then right as the temp starts to rise, switch the a/c off does the temps immediately fall back to normal? What noises do you hear if any?

I know by this time you'll be getting frustrated, and may think you know all those patterns, but nothing substitutes for logical, repeat testing
 






It's intermittent, today, going to work, and coming home for lunch just a few minutes ago it didn't act abnormal at all.

Idling, and speeds less than 20-25 it won't act up.

It's mostly just on the highway, and at 65-70 mph.

No noises, other than the usual fan sound.

If I turn the AC off when the temp gauge goes up, it very quickly falls back down to where it normally is. Goes back up when I turn it back on.

Oddly enough, it didn't do it today going to town or coming back.

It was suggested that the AC compressor might be seizing up, but i'd have thought if so, it would overheat regardless.

The funny thing is...when the gauge shows hot, the engine doesn't seem hotter than normal. I know it's not scientific, and I don't have one of those temp scanner things, but it doesn't feel like it's overheated or have that extremely hot engine smell....
 






The funny thing is...when the gauge shows hot, the engine doesn't seem hotter than normal. I know it's not scientific, and I don't have one of those temp scanner things, but it doesn't feel like it's overheated or have that extremely hot engine smell....

You can get one of those ELM327 OBD-II scanner dongles on eBay for less than the cost of a Happy Meal, and the app for either an iPhone or Android phone can be free if you want just the simple readings like temps. I prefer the WiFi version, but they make Bluetooth versions of the dongles also. Well worth having for issues like this.

I think if the a/c compressor was seizing up, it wouldn't be intermittent and there'd be a lot more noise. How is the a/c compressor belt - proper tension, not too worn?
 






Yeah, it's good to go.

Thanks all! :)
 












It seems like it.

Swear to god, sometimes I think this thing is possessed LOL
 






How about needing oil added to the a/c system? I have seen where there is oil for the a/c system. Could be needing it to lubricate better at the high speeds.
 






I think I'm going to say this is fixed. For the last 3 or 4 days (and it's been hot, mid 90's) it hasn't acted up at all.
I've ran it hard on empty backroads, a lot harder than I normally do (i actually baby this thing around for the most part), and the gauge barely moves at all now.

Last night at lunch break, a co worker rode with me to a local one-off ice cream place, by the time we got back to work, he was complaining about being cold. I was cold too. That didn't happen before LOL.

Just wish I'd changed the CHT sensor first! Saved a few bucks..

Anyway, as it's said; all's well that ends well...or somethin' like that.

Thanks all! :D
 






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