A/C problems, help me diagnose

Leros

Lifer
Jul 11, 2004
21,867
7
81
2000 Nissan Maxima GLE, 110K miles

About three months ago, I took this car on a 400 mile drive, halfway through the engine got pretty hot and the A/C started blowing out hot air for the remainder of the trip. We pulled over to buy gas and the A/C worked for about 5 minutes til the car got hot again. I got the radiator flushed and the engine never overheated again.

(Note: This trip was the first time I know of the car making a long drive in heat. It was 80-90F when it overheated the first time. I just got the car and had only driven it during winter with little A/C or with the heat on.)

After that, the A/C has been acting up. After about 200 miles of driving, the A/C will cycle between hot and cold air. 10 minutes hot, 10 minutes cold, repeat forever. In city driving, the A/C functions fine.

I took it to a mechanic, he ran the car for about three hours and found no problems.

I took it to another mechanic who ran the car for 15 minutes and told me I need a new condenser coil as mine has bent fins. He quote $500 parts + labor. Eek. Would a condenser coil match my issue?

I then took it to a Nissan dealer, who ran it for about 7 hours and found no problem other than the freon was a tiny bit low. He recharged it, but said nothing was wrong and that the freon probably wasn't the cause.

I do a lot of 400 mile driving in 100F heat, so I really want to get this fixed, but I don't want to waste $500 on something that might not be the problem. Its a pain because I can't recreate the error without going on a long drive.
 

cprince

Senior member
May 8, 2007
963
0
0
It could be a bad temperature sensor that shutdown the A/C compressor even when the engine is not overheating, or your engine is still overheating. Either way, I'm thinking that something electrical causes the A/C clutch to disengage. It could also be a bad cabin temperature sensor or a bad air mix door motor.
 

Leros

Lifer
Jul 11, 2004
21,867
7
81
Since I've had no luck with mechanics. I'm thinking about just starting to replace components. I've been told that even a total A/C replacement might not fix it if sensors are broken.

Should I just replace every sensor related to the A/C to start with?
 

nakedfrog

No Lifer
Apr 3, 2001
61,922
17,684
136
That sounds rough. I'd wonder if the condenser is freezing up on long drives. I'm not sure what would cause that or fix it.
 

Iron Woode

Elite Member
Super Moderator
Oct 10, 1999
31,266
12,783
136
there were no error codes due to bad sensors?

does the engine run rough?

do the blend doors use vacuum control?

is your cooling system functioning correctly?

is the fan turning on when it supposed to?

is there any blockages in the front of the car?