Climate control problems? Read This!

[gadget73]

If the AC compressor isn't running, you will most likely get warm air out of the system. The seals around the blend door probably weren't perfect 20 years ago, and they've gotten worse. It also sucks air in from right below the windshield. Hot air from the engine bay usually gets blown out there so thats probably some of the heat.

If your AC system is still R12 you'd probably want to see if there is any refrigerant in there. Probably its dry. If it is, I'd suggest an overhaul of the AC system, this would involve a new orifice tube, a new receiver/drier, new O rings on all the hoses, and a flush of the system. New hoses are also a good idea if you've got some bucks to spend. If you don't have the equipment to properly service an AC system, I'd suggest having a shop do this for you.

The hot air out of the floor vents is possibly a broken air door. In the air plenum there is a door that siwtches from dash to floor, and often the "hinge' breaks, letting air sort of go everywhere. Mine is busted, I just haven't been inclined to rip the air plenum out of the car to fix it.

[1987cp]

I'd add to that to make sure if it's recharged at a shop (especially with megabuck R12), to make bloody sure they pressure test the system before giving you the car back. I wasted all kinds of money in about '99 having a Ford dealer go through the system and replace all the O rings and recharge it, only to call them a couple days later asking why the system isn't cooling and be told "well, the condenser could have a leak in it ...." ... Come to think of it, I'm not sure they replaced the dessicator, either, which I've since been told is absolutely necessary most any time the system is opened up, and that a new dessicator must be installed within two minutes of removing the plugs it's delivered with or it's bad. Long story short, I don't think those guys should have been working on A/C systems.

[Nathan in MI]

If they have any idea what they're doing, they should have put the system under a vacuum for a period of time before recharging it, so that any leaks in the system would present themselves...sounds like in your case, they failed to do that.

[P72Ford]

I'd add to that to make sure if it's recharged at a shop (especially with megabuck R12), to make bloody sure they pressure test the system before giving you the car back. I wasted all kinds of money in about '99 having a Ford dealer go through the system and replace all the O rings and recharge it, only to call them a couple days later asking why the system isn't cooling and be told "well, the condenser could have a leak in it ...." ... Come to think of it, I'm not sure they replaced the dessicator, either, which I've since been told is absolutely necessary most any time the system is opened up, and that a new dessicator must be installed within two minutes of removing the plugs it's delivered with or it's bad. Long story short, I don't think those guys should have been working on A/C systems.

Any shop that is worth a damn will pressure check the system before they charge it.

Last year, I spent about $90 to get my A/C working well (blew 38*F). I replaced all the o rings with R134a units, removed the compressor and got as much oil out of it as possible, had it evacuated and charged. I bought a retrofit kit (just fittings and oil) for $30 too. It worked awesome. Later I installed an aux. fan to blow more heat off the condensor; it made little difference.

This year, I'm going to take everything back apart, replace the dryer/ acuumulator, the orifice tube, maybe the o rings (if needed; but I don't see any leaks), have it evacuated again, and charged. It cost me $50 to have it evacuated and charged.

Gadget, where can I get replacement hoses for my '90 car? Periodically check Egay?

[gadget73]

yeah I've gotten them from ebay, but they're actually listed at a lot of parts stores. There are different hoses by year. 85 and older sets are dirt cheap but totally non-interchangable with later models. 86-91 used the same liquid line. The suction and discharge lines from 86-88 interchange, and the ones from 89-91 interchange. The AC compressor changed in 88 and it uses different fittings.

[grandmarquisdriversince98]

Regarding climate controls.....One thing I noticed on my 88 Grand Marquis is that the vacuum hoses that go to the thermal blower lockout control the heat being sent into the AC. Mine are always plugged up and disconnected from the TBL otherwise it controls the doors in such a way that the AC starts blowing heat when you accelerate instead of cold air. It's not mentioned in the shop manual but I confirmed it by hooking mine back up and then taking it off to have the AC return to normal during acceleration. I think it was to get rid of excess heat detected by the TBL when the cars were new and ran cooler. The only other problem I ever had was with the AC relay that made the AC work intermittently.

[gadget73]

yeah those have leakage problems. Its not supposed to do that, but if its not holding vacuum, it defaults to hot defrost. Mine were sealed up for the same reason when I still ran a TBL.

[Rodentkiller]

I as you know I own a 90 Crown Vic with A/C non climate control. My heater/Defroster went kaput. The fan works and the doors switch from heat to A/C when I move the temp lever but no heat and defrost what could be wrong? Is it a vacumme problem as suggested in the article or is it something else?

[gadget73]

I as you know I own a 90 Crown Vic with A/C non climate control. My heater/Defroster went kaput. The fan works and the doors switch from heat to A/C when I move the temp lever but no heat and defrost what could be wrong? Is it a vacumme problem as suggested in the article or is it something else?

Just noticed this. Either your temperature control cable is unhooked or busted, or there is a problem with the heater core. Perhaps its bypassed or clogged. Non-ATC systems do not use vacuum to control temperature. Its a cable from that slider on the dash down to the blend door.

[DiVin3]

How do you get the atc sensor out

[gadget73]

How do you get the atc sensor out

remove the upper dash pad. Once thats off, the sensor is located above the glovebox, and has 2 or 3 screws holding it in.

[87gtVIC]

Two 7/32 bolts iirc. Not a nice location to reach.

[Mil1ion]

On the ATC system, it is done with a vacuum motor.

Except the 92 CV and MGM in which case it is controlled by a 12 volt motor attached to the ELECTRONIC blend door actuator

shown below

[gadget73]

apparently the 91 is also like this. The vacuum stuff applies primarily to boxes. I don't know the mysteries of the roundy car climate control disaster, other than I want no parts of it.

[sinistral]

thanks for this!
i went to test the TBL and realized the connector in the heater hose was broken, so was leaking coolant! clipped/bypassed the wires, a couple of golf tees in the vac hoses, and removed the broken piece of the t-connector and re-connected the heater hose.

when it warms up around here i'll probably pull the whole TBL and just get a coupling for the heater hose.

this forum is awesome.

Fan motor does not work in floor position
Another ATC bug. The thermal blower lockout switch has probably failed. This is the sensor looking thing in one of the heater hoses under the hood. It will have 2 vacuum lines and 2 wires hooked to it. The purpose of this device is to keep the fan from running when the engine coolant is under 120 degrees. To diagnose this, simply unplug the electrical connector and jumper the two wires. To resolve it, either replace the TBL, or simply bypass it. If removing it, the vacuum lines must be sealed off. Do not connect them together.