Issues with my AC

[Corey872]

Low "coolant" (assume we are talking freon here) can cause what you describe. It will run fine in the morning because everything is already relatively cool, so if the system is limited in capacity (by low freon) it's not a big deal. Once you drive and park it for a while, the engine bay gets hot...maybe sun is now up, so the interior gets hot, too. Now the limited capacity comes into play and you really need to get the air moving over the condensor to get it cool.

Assuming you don't hear any grinding or weird noises, I would go about it like this (order from cheapest to most expensive)

1) Examine the compressor (and surrounding area), ac hoses, hard piping, condensor, etc. Look for any place that seems to have accumulated a layer of oily dirt. Also look around the compressor in a radial line extending out from the pulley. If there is a leak, it will leak oil along with the freon. The freon will come out as a gas, but the oil will stay behind and attract a layer of dirt. This is homebrew leak detection. If the front seal on the compressor is bad the leaking oil will hit the pulley and be flung onto the surfaces radially around the compressor.

2) Start the engine, fire up the AC and make sure the magnetic clutch on the magnetic clutch on the compressor kicks in, and the electric fan on the condensor (in front of the radiator) kicks in. (If the freon is really low, these may not kick in on account of the low pressure cut off switch. May have to proceed to step 3 and add some freon to make them both work)

3) Luckily, we have R134a freon systems, so you can buy a gauge and freon at any local parts store without a license. You can probably pick up a kit for around $40. It will have directions, but basically, it's about like airing up a tire....get the AC running, check pressure, if it's below the range they specify, squirt in some freon, look at pressure, squirt more as needed, then cap the system back up.

4) If you find you have adequate freon, and it still isn't cooling, or there is oil slung all over the place, then it is probably time to call in the big guns.

HTH - stay cool!

Corey

[johnnyapollo]

Hey Corey,

Thanks for the advice. I bought a kit at Advance Auto Parts for $33. Unfortunately, after hooking up the meter, the system is reading "fine" as far as pressure goes (the "blue" zone). Next step is to take it in I guess. At least I can return the kit (I didn't puncture any of the cans nor did I open up any of the packages other than the box).

-- John

[Joe_Black]

I'm with Don on checking the condenser's electric fan. I remember this happening when visiting with you, but forgot to pursue it further by checking fan operation at extended idle and also looking at the fan fuse/relay. Not an uncommon thing to happen, even the fan's connectors can get loose or pinched. The fact it cools fine while moving is a good indicator this may be the problem. Had this happen on one of the Merkurs, easy fix once you confirm.

[johnnyapollo]

The fan sounds right. I checked the fuses - no issues there - I'm not sure if there's a good way to check the relays. I'll climb under it next.

-- John

[Joe_Black]

I'm not specifically familiar with the fan's relay, but an easy check is to "borrow" an identical relay from another system you can temporarily disable while you check the fan. The best time to do the check is after a drive where the engine is good and hot, so the fan will definitely come on while sitting with the A/C running.

[Narsus]

Not that this'll help any, but I have identical symptoms during this super-hot Colorado summer. I haven't delved into it yet, but it cools down at higher RPM's. I'm going to take it in next month, and I'll let you know what they find.

[Joe_Black]

I haven't delved into it yet, but it cools down at higher RPM's.

Are the higher RPM's while stationary? If so, that's your engine fan moving air that the condenser fan isn't.