QuestionQUESTION: I’ve been out of work for way too long. Money is extremely tight, & I really need this car to work so I can work too - & I really like this car. I’ll truly appreciate any assistance you can offer. I’m willing to work on my car myself within my capabilities, & have the service manual but I’m not very knowledgeable or experienced.
SYMPTOMS: Can get only hot air out of dash vents inside for about 20 minutes after I first start it – even w/ Econ set on 60 degrees. Auto setting at 60 degrees gives luke-warm for same time, then gives cold air. Running temp settings up & down several times, I can hear doors open & shut & air comes out of bottom, then dash & defrost vents appropriate to settings, but it’s very hot air. After 20 min. air mix door must be adjusting itself because then I can get cool air w/ 60 degrees & on Econ & cold air on Auto out of dash vents, & gradually warmer & out of the appropriate vents as I raise the temp setting. Am getting F40 code (air mix door problem), which is not surprising to me. This problem will be extremely uncomfortable this summer here in the desert when inside of cars is usually is hot enough to melt plastic objects & kill people & pets!
Is the “air mix” door the upper one of the three? Could this be an electronic / sensor, etc. problem? Or is it likely just a mechanical problem with the door like it needs cleaning? (Mechanical would puzzle me since it works OK after 20 minutes of literally roasting everyone in the car.) What are the best case to worst case range of possible causes & what’s the simplest/cheapest to costliest/most complex range of fixes? Is there anything at all I could try? – maybe spray silicone spray down the air intake in front of the windshield with the car running & Econ w/ fan on high? (That sounds desperate & possibly even dangerous?) I’ve pulled the front part of the dash on a ’78 Cutlass before, but I’m really not sure I’m capable of taking this dash apart & reassembling it successfully. Is there any other way to get to that air mix door?
Thank you so very much! It's a wonderful thing that you do here!!!
Marge in NM
ANSWER: Your fault is most likely the AC/HEATER PROGRAMMER itself. Which is easily replaced by removing the glove box and the under dash panel on the passengers side.
The replacement WILL need to be adjusted properly. You will need several pictures and this websit which is not mine only allows ONE picture, You will have to e-mail: onlineautohelp@msn.com
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QUESTION: Thank you for your prompt answer. Programmer ($$$ yikes!)
Should have told you this before-my mistake: A/C was converted to R134a 2 yrs ago. Had leaking power steering pump R&R’d less than a yr ago. Have put<100 miles on it since. O/S temp read 60o (which was correct) last time I tried to use. Could any of these have caused/contributed problem (like messing w/ AC/heater temp sensors)? Please help me to understand the logic behind needing to replace this $500 part & how I can verify that such an expensive part definitely must be replaced before I spend that much money?
AnswerConverting the system from R-12 to R-134 usually results in illumination of the check engine light caused by a false reading of the low pressure sensor for the AC system.
The R-134 freon is NOT compatable with the R-12 AC system and should NEVER have been converted.
Who knows WHAT has been done to the AC system to make it work properly.
Does the check engine light still illuminate on the dash with a probable code of F46, F47 or F48 ?.
Does the outside temp read correctly ?.
Messing with the sensors can cause faulty information feedback to the AC programmer causing incorrect operation.
What you will need to do, Since I obviously cannot see the system personally, Is to take it to a reputable AC facility and tell them that it was converted from R-12 to r-134 and the sensors were fooled with.
This may turn out to be a very expensive lesson NOT to alter the manufacturers design on ANY systems put on the vehicle.
Replacement of the programmer MAY or MAY NOT be required depending upon what they find was fooled with during the conversion.
