OMG my car is HOT (no ac)

[BlackNSXtacy]

Man, I love my car, but I HATE driving my black on black NSX in the southern heat! My a/c croked on me last week! Has this happened to anyone else out there?

My AC would come on when I first start the car, then blow really cold for about 5-10mins, then just shut down on me. The lights on the ac dash is still on, the compresser(?) still makes that humming noise, but no air.

I had the resistor checked out, the tech bout a new one, switched it out, but still, no good. So, he out my old one back in....
we both were baffled.

Don't know....hopefully, this Tech i just met would be able to ck it out....but he won't be able to look at it for another week! PLZ HELP ME get back into my NSX w/o dying of heat exhauster!

Tan

 

[Soichiro]

Have you checked the sight glass? If not you should do that and report what you find. Maybe find a new tech too, I don't get a warm fuzzy feeling from a guy who changed a resistor to fix a malfunctioning AC system.

 

[tanman]

Originally posted by Soichiro:
Have you checked the sight glass? If not you should do that and report what you find. Maybe find a new tech too, I don't get a warm fuzzy feeling from a guy who changed a resistor to fix a malfunctioning AC system.

Ditto

Tan
2000 Blue NSX

 

[Acuraphile]

It sounds like no air at all, hot or cold, coming from the vents. Please advise.

Bill

 

[BlackNSXtacy]

Well, with the resistor, the reason why it was changed b/c it only runs on high. Not low, or medium. Thats why the resistor was looked at. After the resistor was replaced, it still only ran on high. Wierd. So thats why i'm going crazy here!

Tan

 

[Nsx Service Girl]

I recently ran across a car that had a failed blower resistor AND a failed brain for the control panel....we started with a test panel, it still didn't work, tested the wiring, still didn't work, tested resistor and it was bad....installed new one..yikes!It still only blew high! Put test brain back in car and voila! We had cold air on all speeds. Do you have a friend who might lend you a control panel for testing puposes? I'm very fortunate to have a tech who saved one just for this reason.

 

[Acuraphile]

What you are referring to as the resistor, would that be the Power Transistor? The Power Transistor is a prime suspect for a blower motor that only runs on high. But, possibly, the Climate Control Unit is sending out the 'High' signal, forcing the Blower to go at full speed. If the blower is running full blast, and you have air coming out of your vent, and still have no cooling, then your Compressor is probably not running, or the temperature control function has gone haywire. With the engine running, have someone force the A/C on and off while you watch the compressor. You will see a definite difference in the front pulley of the Compressor as the Compressor Clutch kicks in and out, accompanied by a pronounced 'click'. Also, when the Compressor kicks in, you should see a few bubbles travel across the Sight Glass on the Receiver-Dryer. If the Compressor is not running, it could be low Freon, the Compressor Clutch Relay, the Compressor Clutch, the PGM-FI ECU, a fuse, or the Climate Control Unit, including Sensors. As far as the temperature control going haywire, and the A/C failing after 5 minutes, check to see if the Heater hose is hot where it goes into the firewall. You can usually stop that by removing the control cable from the Water Valve near the firewall, and then forcing the lever to stay as far toward the firewall as possible by tieing it in place. The water in the Heater Core still needs to cool down before you notice much change. This symptom would tend to indicate that the Air Mix Control Motor was set for the Heat mode.

So, if the Blower only runs on high, and the Compressor doesn't run, and the Heater hose at the firewall is hot, or combinations thereof, maybe you are looking at CCU replacement, or some sensor(s) has(have) failed. As you can see by this short process of elimination, a lot of things are involved in troubleshooting the Climate Control, and there is still the built-in Self Diagnosis feature to check for sensor failure, but go the Service Manual to run that. Don't have one? Please get one, ASAP. Good luck.

Regards,

Bill

 

[BlackNSXtacy]

Well, whenever I start the engine, when I turn on the ac, it comes on, COLD! The compressor works, everything. Then about 5-10 mins into the air blowing, it would just turn off. So, I just turn it off. When I roll down the window, I can feel the leftover "cool air" slowly venting out for the fresh mode.
If that made sense, let me know!

Tan

 

[BlackNSXtacy]

Originally posted by BlackNSXtacy:
Well, whenever I start the engine, when I turn on the ac, it comes on, COLD! The compressor works, everything. Then about 5-10 mins into the air blowing, it would just turn off. So, I just turn it off. When I roll down the window, I can feel the leftover "cool air" slowly venting out for the fresh mode.
If that made sense, let me know!

Tan

Ok, let me clear that one up. When the ac turns off, the display for the ac is still on, saying "Auto .......AC" everything, the display stays the same, but no air. thats why I turn it off, I don't want the compressor to work and not have air come out. Thats the wierd part. The compressor and everything still runs, b/c i can feel the vibration and the humming when I turn it on. and goes away when I turn it off. So all thats working, but it just turns off whenver it wants to.

PHEW! hope that made more sense!

 

[nsxtasy]

Are you using either the "AUTO" or "FULL AUTO" settings? Does it still shut itself off if you switch those off so you're in "A/C ON" mode?

("FULL AUTO" means you have the fan speed set to automatic. "AUTO" means that it will cycle on and off depending on temperature. If it only shuts off in the "AUTO" setting, it could mean your car is simply as cool as the setting, or it could mean you have a faulty temperature sensor.)

[This message has been edited by nsxtasy (edited 01 August 2002).]

 

[Acuraphile]

The following advice applies only if you have determined that the Compressor is running, and that the Blower is not, despite doing every possible switch setting. If I have understood everything you have written, the actual symptom is that the Blower stops completely after running at full steam for about five minutes, and that you have cool air up until that time, and that if the Blower were running, you would have cool air?

Like I said, a full speed Blower is caused by the Power Transistor fully conducting. Usually, it is a shorted transistor, but could be a full speed signal from the CCU. Also, a shorted transistor doesn't usually unshort itself, but is shorted forever, and you have tried a replacement.

Sorry that I don't have the wiring diagram with me, so you will need to get one to know what color wires to use for measuring the voltages. You will have to measure voltages when the problem is occuring. A 12-volt reading across the Blower power leads indicates that the Blower should be going full speed. A zero volt, or near zero volts reading indicates that the Power Transistor is not conducting. A possiblity with a 12-volt reading is that the Blower Motor winding is open, but does not indicate how it could keep repairing itself with each cooldown. You will need to measure the resistance of the motor's winding to determine if it is open, or an infinity ohms reading at the time of the failure.

Also, measure between chassis ground and the + power lead of the Blower. It should read 12 volts, or thereabout, when you are running the A/C. I can't believe this is bad, but just check.

Now, if there is 12 volts across the Blower, and it is not running, the Blower would be suspect. Zero volts, or near zero volts across the Power Transistor indicates it is fully conducting, and the Blower should be going full speed. If you read around 12 volts across the Power Transistor, collector to emitter, then the Power Transistor is open (not conducting) at this time. If there is some voltage on the 3rd lead of the Power Transistor,(base)then the CCU is probably trying to control the Blower.

Everything said, I am leaning toward a bad CCU, but I am not there, and you are, so you will have to figure it out. I am afraid you do not have the expertise to handle the steps I have given here (no insult intended), but maybe someone can help you. You need a good multimeter, the wiring diagram, and the ability to understand the diagram and the voltage readings. I would test the Blower with the battery voltage, and the Power Transistor with the meter, and force the Power Transistor to conduct with another small adjustable voltage source feeding the base lead. If I could eliminate those items as problems, then I would see if I could get a used CCU to try out. You could, of course, try and force the Blower to run with another voltage source, and if the Compressor runs like you say, the cold air would be back.

Sorry, but there is no pat answer for your problem. It just has to be tracked down. Good luck.

Regards,

Bill

 

[BlackNSXtacy]

Well, when I was at the shop when the mechanic(electrician) was looking at it, all he did was testing. From my knowledge of just sitting there and watch, I saw he moved from the fuse box, to blower, to transister, to battery, the bigger fuse box(sorry for ignorance!), everything that had to do with the electrical probability.

I sat there and asked him questions on why he was doing it, he just said, I'm trying to find where the short is. Everything semed to check out right(to me). If it was my guess, it would probably be the in-dash controls(CCU?).

I'll see if I could find another ccu to test it out. if not...well, lets just hope thats the problem!

Thankyou SOO much for taking your time out and replying back Acuraphile, I am much appreciated.

Tan

 

[anvil]

Tan,

If it turns out to be the control head, then it is not impossible to repair these. Mine would not turn on the heat or open various vents even though it showed the correct settings on the display. I took it to an electronic equipment repair service. They found bad "capacitors" and replaced them. The unit works fine now. Cost was $100 plus tax, ... considerably better than the $650 plus a dealer said the new unit would cost.

Good luck with yours.

anvil