A/C works good when driving but warm at idle

[767Jockey]

This has probably been covered on here, but I didn't see anything applicable in search. If I missed a previous answer, I apologize for re-posting. I have a 2005 T'Blazer with the straight 6 engine. It's the normal T'Blazer, not the extended version, and it has manual, not automatic climate control. It's got 105,000 miles on it, and I have never had to have the A/C serviced before. All the components are original to the vehicle from new. Just like the title says, the A/C blows plenty cold once the engine revs are up a bit, either driving or while the TB is parked. However, at idle speed, the A/C is warm. Is this a common issue? Anyone have any ideas? All I have done so far is but one of the do it yourself kits for adding the gas to the system. The gauge on the kit when properly adjusted for outside temp showed low. I brought it up to spec and it still does the same thing. The only change I saw in that was now the A/C is a bit colder when driving, however no change in the warm air at idle problem.

Any help on this would be greatly appreciated. Thanks!

 

[The_Roadie]

Home-based gauges and kits are not the most accurate way to keep your system in spec. A professional can evacuate the system, check for leaks, and refill it with the exact amount needed. IMHO, it's not wasted money to take a vehicle to a trusted AC specialist with good on-line reviews (such as on Yelp or the BBB). A professional can also check to see if the pressures are in spec at idle, that may indicate a compressor wearing out. Too much refrigerant is equally bad as too little, and some home-based kits encourage overfilling.

That said, if AC performance at idle is worse than at speed, then you have to suspect airflow through the radiator/AC condenser area is low. You might check for obstructions/debris in the fins or between the two units. Bent fins from pressure washing that got away from somebody. Mud, dust, leaves.

Fan clutches can also be at fault, but they were redesigned sometime in 2005 model year to improve reliability, but the PCM was also changed to force the fan clutch to be more engaged at idle right after a cold start on a hot day, because that's when the cabin needs the most cooling but the engine is NOT hot so normally there would be little airflow commanded by the PCM. A 2005 vehicle may or may not have that updated programming, and I don't have a copy of the TSB handy that might have said which vehicles would need it. A dealer is the only way to get that PCM reflash, and they could also look up your VIN and see if you need it. Many dealers charge what I think of as an unfair price for that service (1 hour minimum for ten minutes work), so you will want to ask them what they charge for the look-up service, and then for the update if it's required.

 

[bmcutright]

Roadie, are there any other options than going to the dealer for a reflash? I need a new headlight driver module relay, gonna replace the clutch fan relay at the same time now that I've looked into these related posts. Would you recommend it for an 04?

 

[The_Roadie]

Only a dealer or a pcmofnc tune can get you the 2005 update. Do you have poor cabin cooling on a cold start on a hot day?

 

[bmcutright]

Yep, and a rough idle when I first start up too