AC UPDATE/NEW FAN

Okay so I finally bit the bullet and bought the Duramax fan blade part# 1580690 with severe duty clutch part# Hayden 2851.

@L31MaxExpress suggested this pairing for the most cooling possible, and so far it has not disappointed, though I’m hoping to tweak it just a little more.

The fan fits in the shroud BARELY on my OBS Z71 Tahoe. I drove it around to make sure it isn’t hitting at all, and while it never came in contact with the shroud…it is still a little too close for my comfort. I will trim the shroud ever so slightly to ensure enough room for any flex.

First impression: This MF COOLS the engine. I’ve never had my 5.7 stabilize at 187 degrees on a 100 degree day. That alone impressed me the most and worth the upgrade.

What I don’t like too much, the clutch is not engaged as much and takes a while to engage. I’m wondering if I can adjust the spring to make it lock in a little sooner.

Holding 1500rpms with the AC on high, fan DISENGAGED, the AC compressor will cycle off from the high pressure. It will do this for a few minutes until the fan clutch locks in, and when it does…WOW. AC turns cold, and the fan is incredibly loud. My issue is that the Clutch will disengage after about 30-45 seconds and repeat the above process with the compressor cycling until it locks in again. Engine temps are in the 180s during this so it really is cooling, no doubt.

At idle, AC is cooler and the engine does not get over 190. On a 100 degree day like today, engine temps would creep up to around 205-210 and the AC compressor would cycle off. The compressor stays locked in at idle now with vent temps at 58 degrees.

The pressure is too high for the AC regardless, I don’t know why anymore. I can only assume it’s because the serpentine style condenser? Can anyone verify if my 2000 Z71 Tahoe would’ve come with a parallel flow condenser or serpentine?

Either way, I love this fan!

Too close for comfort. I have trimmed the blade itself slightly on 2 of those fans now although trimming the shroud could work too. Sharp heavy duty scissors will go through either like a hot knife through butter. As for high ac pressure, a more effective parallel flow will drop the pressures but apparantly they are becoming nearly impossible to find from the feedback of others. Even the part number I have bought several nice parallel flows under is coming in as a serpentine style. It is like a bad joke.

Do you have the pusher condenser fan? What do you have in the way of coolers in front of the radiator? My 99 Tahoe had the factory electric pusher. I added a pusher to my 1987 G20 build.

I have swapped my 97 to the EV Fan clutch and I actually ran the EV clutch with a simple relay on Fan 2 output for a while. On the 97 van the fan opening is slightly offset from the radiator centerline. I was able to get a 16" electric puller offset in the shroud to the driverside of the radiator. Fan 1 turned on the electric fan. Fan 2 engaged the clutch. Before I put the EV clutch fully under P59 control that setup was pretty darn effective. The Duramax fan would move a decent amount of airflow just freewheeling, the electric fan would increase the airflow, then last resort engage the clutch.

I feel like sombody with Arudino skills could easily build a standalone PWM controller with RPM feedback from the fan to optimize the EV clutch in a retrofit application. I would feed engine rpm, engine coolant temp, TPS, transmission fluid temp, and provide the auto-recirculate pressure switch state, and the fan rpm to the Arudino. Then form some kind of code that took into account those inputs to control the fan clutch.

L31MaxExpress said:

Too close for comfort. I have trimmed the blade itself slightly on 2 of those fans now although trimming the shroud could work too. Sharp heavy duty scissors will go through either like a hot knife through butter. As for high ac pressure, a more effective parallel flow will drop the pressures but apparantly they are becoming nearly impossible to find from the feedback of others. Even the part number I have bought several nice parallel flows under is coming in as a serpentine style. It is like a bad joke.

Do you have the pusher condenser fan? What do you have in the way of coolers in front of the radiator? My 99 Tahoe had the factory electric pusher. I added a pusher to my 1987 G20 build.

I have swapped my 97 to the EV Fan clutch and I actually ran the EV clutch with a simple relay on Fan 2 output for a while. On the 97 van the fan opening is slightly offset from the radiator centerline. I was able to get a 16" electric puller offset in the shroud to the driverside of the radiator. Fan 1 turned on the electric fan. Fan 2 engaged the clutch. Before I put the EV clutch fully under P59 control that setup was pretty darn effective. The Duramax fan would move a decent amount of airflow just freewheeling, the electric fan would increase the airflow, then last resort engage the clutch.

I feel like sombody with Arudino skills could easily build a standalone PWM controller with RPM feedback from the fan to optimize the EV clutch in a retrofit application. I would feed engine rpm, engine coolant temp, TPS, transmission fluid temp, and provide the auto-recirculate pressure switch state, and the fan rpm to the Arudino. Then form some kind of code that took into account those inputs to control the fan clutch.

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Yup I have the factory pusher fan! It runs strong, and all day.

Only other thing on the cooling stack is the factory transmission cooler which is also running cooler with the duramax fan.

I’m going to adjust the spring on the clutch so it locks in sooner and I believe I’ll be satisfied

I also meant to ask what pressure the compressor is cutting off at? I found that some of the generic pressure switches that are being cross-referenced cut the compressor at 275-280 rather than the correct 410-420 psi. I fought that for half a summer in my 97 Express before I figured out it had the wrong pressure switch via reading about it in the FSM.

L31MaxExpress said:

I also meant to ask what pressure the compressor is cutting off at? I found that some of the generic pressure switches that are being cross-referenced cut the compressor at 275-280 rather than the correct 410-420 psi. I fought that for half a summer in my 97 Express before I figured out it had the wrong pressure switch via reading about it in the FSM.

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Yeah I just recently replaced that switch with the correct one that’s rated at 430 psi. Hot idle baking in the 100 degree heat, the pressure is around 400. When held at 1500rpm, the pressure goes over 430 and kills the compressor, starts cycling every 15 seconds or so.

Once the fan engages at 1500, the compressor will stay locked in though, until that clutch disengages again.

I should also mention that below 95 degrees, AC has no issues at all. Never cycles, and stays around 300-340 psi

What temp thermostat are you using?

GoToGuy said:

What temp thermostat are you using?

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Whatever the factory called for. 190? I replaced it a few years ago with a factory replacement. 190 or 195?

JohnZ71 said:

Yeah I just recently replaced that switch with the correct one that’s rated at 430 psi. Hot idle baking in the 100 degree heat, the pressure is around 400. When held at 1500rpm, the pressure goes over 430 and kills the compressor, starts cycling every 15 seconds or so.

Once the fan engages at 1500, the compressor will stay locked in though, until that clutch disengages again.

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I feel like I never saw over 350 psi on either my Express or Tahoe with the factory 11 bladed fans with R134a. Potentially overcharged or air in the system. Are you able to recover 6-8 oz and see if that helps the situation? Capacity should be 3 lbs or 48oz.

L31MaxExpress said:

I feel like I never saw over 350 psi on either my Express or Tahoe with the factory 11 bladed fans with R134a. Potentially overcharged or air in the system. Are you able to recover 6-8 oz and see if that helps the situation? Capacity should be 3 lbs or 48oz.

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I don’t have the equipment to recover/charge the system. My AC guy does it and puts the exact amount in, whatever it calls for. I’ll dig up the latest receipt and see if it has the weight of 134 on it.