AC problem on 89

[John White]

I have an 89 with 40,000 miles that has an AC problem. I'm hoping someone here can offer a solution.

I rarely drive it more than 15 to 20 miles and the problem happens on longer trips. The first time it happened was about 4 years

ago. The alert showed that I had low refrigerant level. I went to the dealer here and ended up converting from R-12.

A year ago I had the same alert on a 100 mile trip. I took it to dealer and was advised that refrigerant was just slightly low.

They evacuated and filled the system, but could not find a leak.

Well, last week was the first long trip since and I got the same alert. Strange thing is, when the alert comes on the air blows

warm. After getting home driving around town AC works fine and no alert.

It seems to me that this has to be a problem with a sensor or some other electronic device as opposed to refrigerant actually being low.

I talked to the owner of the dealership and he said that with the problem being intermittent it would be hard to diagnose. He said if I could

give him an idea of what is causing this, he would take care of it.

So, I'm hoping that one of you folks might have had this problem and has an idea of how to solve it.

Thanks, John

[harry yarnell]

Why did the dealer evacuate and recharge when the system was 'slightly low'? A simple gauge test would determine if the system needs Freon now. I hope 'they' add oil when the system is evacuated, and when 'topping off', from time to time oil MUST be added to replace that which leaks out with the Freon.

See what the gauge test shows. Sounds like a small leak (they're the hardest to find) to me.

[TexasJohn55]

Sounds like a classic case of evaporator freeze up. This can happen when the system is low on freon and there is limited air flow across the evaporator such as fan speed set to low setting such as on long trip after cabin has cooled down. The evaporator is eventually covered with ice and air flow reduced even further.

The other scenario is that the low freon causes the compressor to cycle off too frequently and reduces cooling. Either way, add a can of freon.

Edited February 12, 2016 by TexasJohn55 (see edit history)

[John White]

TexasJohn, Evaporator freeze up sounds logical for the symptoms. I'll suggest this when I go in. Thanks

 

Harry, I said the same thing you did. But they insisted that they couldn't just top it off. They said that the only way to add to that system

was to evacuate and recharge.

[ol' yeller]

I know 89s are different but did it set a code? On my 90, when those warning lights come on,it also sets a code that tells you where to look.,i.e. where the code was set from.

[Barney Eaton]

_{I also go with the evaporator freeze..... and it might be partially caused by the lack of airflow thru the evaporator.}

 

_{One problem that can happen on the Reatta is an accumulation of lint, pollen, hair, etc on the outside of the accumulator which restricts the flow.}

 

_{Restricted airflow could contribute to the evaporator freezing.}

[Guest Corvanti]

i agree with all of the above. one thing i do instead of cutting the fan lower if it's getting too cold, i put it on bi-level - if that is the problem.

 

it shouldn't be a problem to check the evaporator for crud yourself.

 

i'd also find a reputable A/C shop to take a look at it. seems the dealer just wants your $$$. a shot of coolant (134a)? and a leak check would be my next step.

 

hope this helps.

[waltmail]

An '89 with 40,000 miles might be the problem with any leaking. The system has a bunch of oil seal o rings. When the A/C is not used often enough, the O rings might dry up and flatten. This would  cause system leaks.

[Guest Rp1967]

Dye and a black light are your friend when it comes to finding small leaks.

Have them install the dye and you can buy a black light and do some diagnosis on your own.

[Jim]

Especially when converting to 134 from R12 the computers can get some false information and set a code and shut off the AC.

R 134 uses different pressures and temperatures from the R 12

Since it appears your quantity of freon is maybe not the issue. Simply reset the codes and the AC will probably start working again.

My sister has had this situation several times and always when she needs to reset the codes she calls me and I tell her how. The last time I told her to write it down as I wouldn't be telling her anymore.

Here is something I have saved on my computer for folks needing to read out or reset the codes.

You can do it while driving but best to pull over to the side and reset them.

AC codes are B446, B447,  B448 and B449

 

88-89

BCM means Body Computer Module and controls the functions of the body.

ECM means Engine Computer Module and controls the functions of the engine.

IPC means Instrument Panel Cluster.

With the key on, engine running or not, go the climate screen on the

CRT and press and hold the off and warm buttons at the same time.

The service engine soon lamp will light and the ECM codes will be listed

followed by the BCM codes and then the IPC codes.

They go by quite fast so you may want to write them down. Any code with a

"h" after it will be a code that was current, but is not now, and is listed

a "history" code. Any code that does not have an "h" is a current code.

ECM codes will start with a "e" and then 3 digits, BCM with a "b" etc.

After the codes are listed the screen will say ECM? This means do you want

to diagnose the ECM.

If there were "e" codes push "yes" if not, push "no" and the screen will

go to the BCM?

If there are ECM codes after pushing "yes" it will ask several questions.

Keep pushing "no" until the question "ECM code reset" comes up and then

push "yes".

You can go from the ECM to the BCM and then to the IPC and clear any codes.

You can't hurt anything by doing this procedure and even if you make a

mistake simply push "end" or shut off the key and everything will go back

to normal.

 

90-91

Turn on the key and on your ECC ( climate control module ) push the "off" and temperature up ( up arrow ) at the same time and hold them until the car goes into the diagnostic mode. You will see all of the lights on the IPC light up and the trouble codes will then be read out where the mileage usually is.

Write down the codes as they go by. They go by pretty fast so write them down quickly and watch for the next. First you will get the engine codes eg. Exxx, then you will get the body codes eg. Bxxx then some IPC codes eg. Rxxx and maybe an SIR code.

If any code has an "h" after it that means it is a code in history and not current. No "h" means it is a current code.

After all the codes have displayed you will get a Ec? this means do you want to diagnose the engine computer. Pressing the Fan down arrow you will be telling the computer no, the fan up arrow means yes.

If you did get any Ec codes and you want to clear them, when you get the Ec? push yes and then it will ask you questions, keep pushing no until it asks if you want to clear the E codes then push yes.

If you have no E codes and/or want to go to the B codes when it asks you Ec? push the fan down button for no and it will then ask you Bc, and you can push yes. It will then ask you questions and you continue pushing no until it ask CLR b code and you push the up fan for yes.

You cannot hurt anything or screw up anything by doing this and if you make a mistake simply turn off the key and start over or push the bi-level button next to the fan switch.

 

Edited February 10, 2016 by Jim (see edit history)

[John White]

Thanks for all the input on this. I hope to go in next week to see if they can find leak. Of course I won't know for sure if it is fixed until I take another longer trip.

I'll let you know what happens.

[padgett]

Just a note but there are two warnings that display: "LOW" which is common at about 60F and a misread, at 90F there is an issue. And VERY LOW which also turns the compressor off and will not restart until you disconnect the battery and reset everything.

 

You can watch the compressor operation on BD28. Will start around room temp when the compressor is off then draw down as the compressor runs. When it drops below 0, the compressor will cycle. The compressor should be on more than it is off.  See here for more information.