1998 Civic EX D16Y8

A/C functions well... except when the outside air temp goes up. It seems that when it gets above 95-100F or so (especially with the sun out) the compressor simply won't come on. Once the temp goes down (especially after the engine has cooled) the compressor will come on and cycle like normal... provides cool comfortable air (but not COLD).

Any thoughts?? Hooked up the gauges and it appears that the a/c system is charged properly.

Thanks,

Curtis

 

Does the condenser fan also fail to run when it's hot outside? Does the condenser fan ever run?

What were the low and high side pressures when the A/C won't work?

 

The condenser fan does engage. Gauges read around 40psi on the low side and around 240 on the high.

Ran through the troubleshooting flowchart in the book... checked the relay, the connection to the compressor, continuity, etc. with the volt/ohm meter. No problems. So for fun we disconnected and reconnected the battery and by golly the A/C worked again. By the time all that had taken place the sun had gone down and it had cooled off to around 80.

A few days later... got up to about 100F again. Left the house (where it was parked in the garage) and the AC ran fine. Idled at a red light for about 3-5 minutes... then it stopped coming back on until later on when the sun went down and it started cooling off.

 

When it's hot outside and the compressor clutch disengages:

Does the condenser fan also turn off? Or does it still run?

 

Shoot.. good question but unfortunately I didn't notice. All I did notice was that when the compressor subsequently "would have" come on the condenser fan did.

 

Measure the clutch clearance and the coil resistance.

 

i had a similiar problem with my civic a few years back, the previous owner said he had added refrigerant to couple of times and i did once as well, but once it got really hot out it would stop cooling. So what i did was pull out the refrigerant, added some compressor oil, put it on a deep vacuum and weighed in the exact amount off refrigerant listed on the data tag under the hood. I also cleaned the bugs/debris from the condensor and it worked like a brand new. So in short the continous topping off the refrigerant charge must have introduced air/non condensable into the a/c system causing it to run higher psi, and with higher psi=high temps. I also did a leak check and found a failed o-ring gasket on the discharge gas line from the compressor. Hope this helps

 

This sounds plausible or I was thinking a resistance change due to temp. As RonJ@HT said, measure coil resistance. Cheap digital multimeters at Harbor Freight (I think I paid $3 for mine).

 

Coil resistance appears to be within specs.. haven't had an opportunity yet to measure clutch clearance.

This is pretty close to the theory I have about the whole thing... I've owned the car since 2003 and over time I've periodically added refrigerant with a cheapo R-134a "top-off" kit... includes a low-side gauge but not the high-side gauge. I suspect over time I've overfilled it and my thought was I got too much refrigerant oil in the system.

Condenser is clear of most debris and I just vacuumed out the empty hole at the evaporator core (where I plan to install a cabin air filter.. US Civics didn't include them at the time).

I haven't added refrigerant for over a year and a half.. I don't think the system is leaking. In the past 2-3 years my knowledge of a/c systems has expanded and now that I have good high-low gauges instead of a cheapo low gauge I can make better decisions on whether to add or not. I also take ambient temp into consideration when checking the pressures.

Once I get a hold of a good vacuum pump I plan to suck the system dry and see if I can determine how much oil is in the system.. and drain or add as necessary so not only will I have the *exact* amount of refrigerant but also oil.

Thanks all for the suggestions.. I'll keep everyone posted.

Still waiting for the temp to hit 95 again so I can test it out again!