Not to hijack this thread, but any thoughts on how necessary the condenser fan is? If temps are OK and I'm monitoring via UltraGauge, then it's not the end of world right?

I have no clue how much air that thing moves.

 

Well, in my view the primary function of the aux fan is to help remove heat from the condenser when the AC is on and the vehicle isn't moving fast enough to accomplish this "naturally". The second function would be to aid in engine cooling when the engine is struggling to do it itself. Kicking on the aux fan will supplement the air moving across the radiator via the mechanical fan and hopefully assist in cooling the truck. The aux fan does move a good bit of air however forcing it through clogged fins of a condenser will reduce the effectiveness. If the condenser is pretty clean then it will work much better. There's a reason the ECU turns it on, I would not want to deny it the ability to try and cool itself if it thinks it needs to. This is a Disco we're talking about!

More importantly, I've been working in Boston every month for the last 10+ years and am plenty familiar with Boston traffic. Trying to get out of the city at 3pm on a Friday in the summer is effing suicide, no other way to put it. And no way would I attempt to drive around Boston with no aux fan in the summer months. Not only will your AC suffer horribly, you may as well put headgaskets on one of those Amazon recurring shipment things. LA traffic is bad with 4 million people in the city. but despite having less than a quarter of that in Boston there are far fewer major thoroughfares to travel on, and most of them are two or three lanes. Boston traffic is some of the worst around in my opinion. Even disregarding the potential for blowing a headgasket, the AC performance relies too much on the condenser fan to not have a functional one.

Is it necessary, possibly not if your driving habits don't often put you in a position to need it. Is it worth not having? I say no way.

 

I think I'm going to hold off on swapping the fan for now and see whether it's needed. In my mind, let's look at the two purposes of the fan:
1. Improving AC performance in low-airflow and warm ambient situations. If this extra fan isn't there, then the AC performance is degraded, but the dual pressure switch will continue to operate normally and prevent any actual damage to the AC system. Risk overall is low, and warmer cabin air isn't the end of the world.
2. Assisting with engine cooling in potential overheat situations. This only kicks on at 212F - I've only seen that number on my truck once, and since then, I've changed my coolant and replaced the thermostat, water pump, fan clutch, and fan. The truck is now running 186-188 on the highway and 190-194 in traffic. I haven't seen those numbers change when adding AC, but if it does start to rise above 200F, I can always just turn off the AC. Risk here is pretty low as well, since I'm monitoring temps constantly and not just relying on the idiot light on the dash.

I'm thinking that the severe duty fan clutch and higher-CFM fan, in place of the OEM components, can compensate for whatever airflow the condenser fan would end up pulling through. It should be easy enough to tell, based on the AC performance and the engine temps. I just don't want to knock a hole in my condenser and have to pull the whole system apart again - I think it makes sense to wait and see whether the extra fan is necessary, or whether the cooling system upgrades and better airflow I've already added can effectively take its place.

You're right that Boston traffic is bad, but it's only really devastatingly hot here a couple weeks a year - if I were living in Houston it'd be a different story. Plus, the truck isn't a daily driver so I'm not going to be idling around in traffic every day with the AC blasting. The cooling system is keeping the truck cooler now than it was when it left the factory, and I'm not solely reliant on the idiot light on the dash to tell me if it's getting warm. Seems low-risk, overall, to me.

 

Not driving the truck much does the most to lower the risk. I don't think it's a crazy idea not to fix it, I just happen to like good AC and don't like overheating. I also think the upgraded fan you're running will make a difference so it's certainly worth trying out before jumping in, especially if ruining your condenser in the process is also a risk. I'm definitely interested in the results. My guess is that in any kind of summer stop and go, the AC will be useless, not just warmer in the cabin. Hopefully I'm off base. You're right, there are lots of people driving around with seized fans who don't even know it. Both my trucks were when I got them.

 

I don't have that many data points yet, since hot weather in Boston is still a few weeks out. That said, this afternoon, it was 80 degrees and I drove 15 minutes across town to pick up lunch. The coolant was up to temperature by the time I got there, and I left the truck idling outside for maybe 5 minutes - came back out to see 188 on the Ultragauge and cold air coming through the vents. I'm also interested to see what happens when sitting in traffic for half an hour at 95 degrees, but I'm optimistic. The upgraded fan and severe duty fan clutch moves a ton of air (unfortunately, I haven't been able to find CFM specs so that I can quantify this though).