Automotive Air Conditioning Information Forum

71403 wrote:Verify the recirc door is fully closing along with heater control valve operation.

Vent discharge 30deg under ambient in non-recirc mode rings a bell as "normal" on most systems... which is where you are at idle. A partially open recirc door will often cool at highway speed but not slow/stopped.

evaluated as well. recirc and blend door ops normal. no heater control valve from the factory, so did the "ranger mod" to add a vacuum actuated heater core shutoff valve when in "MAX AC" (ie recirc)

all readings above are on "MAX AC" - so zero coolant flow in the heater core, and recirc'ed air.

thanks for the ideas.

Ah, the old defective return received from RockAuto. Because of the distributed wholesale nature of that operation, RTV items that don't get tagged get re-shipped to customers. Just the nature of the system when you run it with the lowest possible operating cost. They do usually make it right.

All of your testing points to an airflow issue. The fact that your clutch no longer locks up at idle is probably most of it, if not all of it. I am sure the defective unit cooled quite well...

The wet condenser test says the charge level is good. If it was badly overcharged with oil or refrigerant is would not drop that far.

There are still plenty of 7.3's on the road here in Las Vegas. Commercial vehicles that idle a lot - shuttle busses Tow Trucks etc. This time of year I can hear the fans on them a block away, well before I hear the diesel clatter. The ones with no fan noise all seem to have the windows down when it is 112f

Once you get a fresh fan clutch in it, try the full load test after the engine is at operating temperature.

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bohica2xo wrote:Ah, the old defective return received from RockAuto. Because of the distributed wholesale nature of that operation, RTV items that don't get tagged get re-shipped to customers. Just the nature of the system when you run it with the lowest possible operating cost. They do usually make it right.

All of your testing points to an airflow issue. The fact that your clutch no longer locks up at idle is probably most of it, if not all of it. I am sure the defective unit cooled quite well...

The wet condenser test says the charge level is good. If it was badly overcharged with oil or refrigerant is would not drop that far.

There are still plenty of 7.3's on the road here in Las Vegas. Commercial vehicles that idle a lot - shuttle busses Tow Trucks etc. This time of year I can hear the fans on them a block away, well before I hear the diesel clatter. The ones with no fan noise all seem to have the windows down when it is 112f

Once you get a fresh fan clutch in it, try the full load test after the engine is at operating temperature.

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yeah rockauto took the return with paid shipping and sent a replacement, no fuss. showed up last night so i'll get it swapped in when i have a minute over the next few days. apparently fan clutches are to be stored face down, so perhaps is related to how they stack them in the warehouse. i unboxed this one and put it face down and will leave in there for a few days. obviously not stored face down once installed though so not sure how much that could matter??

did review the illustrated parts catalog and poked my head around another 7.3 in my lot at work, all of the dams and shrouds seem to be in place.

thanks for your help and input - will let you know what i get.

welp, tenatively, think bohica2xo was correct.

i put the new fan clutch in friday. definitely more air movement at idle, but this clutch actually unlocks after you start driving. it holds on longer than the original clutch, so definitely some different behavior.

haven't had a high 90s day since friday, but first start with the new clutch on friday was lo/mid 80s ambient, and vent temps immediately went into the mid/hi 50s. vents still achieved ~40F at speed.

occam's razor. appreciate the insight and advice from the forum - great first experience.

will monitor for a week and report back.

well, new fan clutch definitely exhibits different behavior. stays locked longer on startup, locks faster while idling.

idle vent temperature performance is better, but still not in the 40s. maybe high 50s. at speed performance remains phenomenal, 40F all day long.

given that every component has been replaced at this point i am only left to assume that this is as good as it is going to get.

wanted to offer my thanks to everyone that weighed in - i appreciate the help!

zj96sc wrote: poked my head around another 7.3 in my lot at work, all of the dams and shrouds seem to be in place.

1. Are you able to try out that truck's performance at idle ?
2. Was that fan clutch you installed a factory or brand-name one ?
3. What about the fan blade itself - is that factory and correct ? Correct number of blades for a 7.3 with tow package ?

1) i dont know that specific guy, but i've got some other 7.3 buddies that can pull some vent temps for me.
2) new in box motorcraft part, p/n YB-3157
3) original fanblade to my knowledge, has a ford part number on it. didn't write it down.