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Old 09-24-2018, 09:07 PM   #1
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1987 34.5' Airstream 345
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Cooling Fan & AC Issue

My OEM electric cooling fan stops working when I turn my dash air conditioning switch ON. The motorhome will overheat in this configuration. When I turn the dash AC switch OFF the cooling fan starts running again and it does cool the motor. I can literally turn the cooling fan on and off by toggling the AC switch on the dash. The AC does provide cool air but I can not leave it on since it turns off the cooling fan. Any thoughts on how to fix this will be appreciated.
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Old 09-25-2018, 01:20 AM   #2
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My OEM electric cooling fan stops working when I turn my dash air conditioning switch ON. The motorhome will overheat in this configuration. When I turn the dash AC switch OFF the cooling fan starts running again and it does cool the motor. I can literally turn the cooling fan on and off by toggling the AC switch on the dash. The AC does provide cool air but I can not leave it on since it turns off the cooling fan. Any thoughts on how to fix this will be appreciated.
Your electric dash air con cooling fan is not the problem. It will help cool the motor, but as far as I am aware, it is entirely peripheral to the set up.

Have you serviced your radiator and specifically have you recently replaced your fan clutch? That would be my first port of call. The clutch runs in various speeds, at first, it is barely audible. At full pelt, it sounds like an airplane taking off in your coach and your temps should drop rapidly. Is it coming on at around 200 degrees? If not, it's duff. Buy a heavy duty replacement, preferably AC Delco.
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Old 09-25-2018, 06:09 AM   #3
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Your electric dash air con cooling fan is not the problem. It will help cool the motor, but as far as I am aware, it is entirely peripheral to the set up.

Have you serviced your radiator and specifically have you recently replaced your fan clutch? That would be my first port of call. The clutch runs in various speeds, at first, it is barely audible. At full pelt, it sounds like an airplane taking off in your coach and your temps should drop rapidly. Is it coming on at around 200 degrees? If not, it's duff. Buy a heavy duty replacement, preferably AC Delco.
This condition started half way through my last outing. We noticed the absence of fan noise and rising engine temperature. In an effort to reduce the load on the engine I turned off the AC. When I did the cooling fan turned on with its typical full roar. Turn on the AC and the fan clutch stops working. I suspect a bad sensor but I haven’t a clue where to look.
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Old 09-25-2018, 06:18 AM   #4
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This condition started half way through my last outing. We noticed the absence of fan noise and rising engine temperature. In an effort to reduce the load on the engine I turned off the AC. When I did the cooling fan turned on with its typical full roar. Turn on the AC and the fan clutch stops working. I suspect a bad sensor but I haven’t a clue where to look.
The fan clutch is entirely mechanical and run off a thermal spring. There is no replacement sensor, you probably need to replace the entire unit. At first, they can just start to stick and not work effectively. Then they entirely give up. It is not the electric fan, it is the thermal clutch which is connected and drives the main five finned metal fan. It looks like this:

https://www.amazon.com/ACDelco-15-49.../dp/B000C9FD6U

That is not meant to be an exact parts match for your vehicle.
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Old 09-25-2018, 06:54 AM   #5
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The cooling fan is electrical. It receives on/off input from both engine temperature and the AC system. This OEM electric fan clutch was installed about a year ago without issue. Google points toward a bad “trinary” switch of which I know nothing. I suspect there are several sensors and switches that might cause this. I am pretty confident it’s not the clutch itself since it does work when it receives electrical input. Puzzling.
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Old 09-25-2018, 09:43 AM   #6
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The cooling fan is electrical. It receives on/off input from both engine temperature and the AC system. This OEM electric fan clutch was installed about a year ago without issue. Google points toward a bad “trinary” switch of which I know nothing. I suspect there are several sensors and switches that might cause this. I am pretty confident it’s not the clutch itself since it does work when it receives electrical input. Puzzling.
I know nothing about electric fan clutches. I thought they were all thermal switches. I think we may be talking about different things. Has your coach had an aftermarket fan added in front of the radiator? Either way, if you have lost the sound like you are taking off in an airplane, then your fan clutch isn't working as expected and that is what will keep temps down.
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Old 09-25-2018, 01:21 PM   #7
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So the fan is spun mechanically, but the clutch is electrically actuated? I've not heard of that.

Regardless, you have an electrical issue. Step 1, check your grounds. More info on how this is all wired would help.


Welcome to the forum, by the way. More info on what rig you have?
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Old 09-25-2018, 02:21 PM   #8
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No, I think we're talking two different fans here.

1) The mechanically-driven fan on the engine is driven by a V-belt, is usually mounted on the water pump pulley, and the fan speed is controlled by a thermally-controlled "viscous coupling" that allows the fan to slip to a lower speed when the air passing the coupling is cool, and gradually locks up when the air around it is hot. There is generally a bi-metal spring on the front of the coupling assembly (also called the fan clutch) that is typically aluminum colored and has fins cast into it to cool the viscous fluid that controls speed. The bi-metal spring also controls final fan speed. These assemblies have non-rebuildable moving parts and bearings inside them, and they do wear out.

2) Many radiators have one or more auxiliary electrically driven fans to add cooling at slow speeds or when the Air Conditioning compressor clutch is engaged to get sufficient cooling air coming through the A/C condenser assembly, which is generally mounted in front of the engine cooling radiator. These fans also may have an electrical thermostat sensor in the liquid coolant plumbing somewhere. They generally run at a fixed speed when energized. They also tend to wear out non-rebuildable bearings and internal parts as well.

What's NOT making sense to me is the increased noise when the Air Conditioning is turned off. Sounds sorta backwards to me. The real question is what's making the noise..the mechanical fan, or the electrical fan? Need to figure that out.

Note that the mechanically-driven fan may not be sufficient to keep the engine cool in slow traffic or with the A/C turned on. That is where the electrical fan is designed to help. Note that BOTH fans should be moving air through the radiator from front to back when they are spinning. Some have noted that the electrical fans have tried to move air the wrong way--possibly because of a wiring error at some point. Something else to check...
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Old 09-25-2018, 02:34 PM   #9
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Thanks for the comments. I loose the “sounds like an airplane taking off” noise when I push the AC ON button on the dash. The noise comes back when I turn the AC button OFF. I can literally engage/disengage the “airplane noise” using the AC buttons on the dash. This is a recent problem. I appreciate your comments. Thank you.
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Old 09-25-2018, 02:50 PM   #10
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Originally Posted by John P View Post
Thanks for the comments. I loose the “sounds like an airplane taking off” noise when I push the AC ON button on the dash. The noise comes back when I turn the AC button OFF. I can literally engage/disengage the “airplane noise” using the AC buttons on the dash. This is a recent problem. I appreciate your comments. Thank you.
In which case, you are not referring to the mechanical fan clutch because that has no bearing on your dash air con setting or any electrical switches. My sense is that you have an aftermarket fan which makes the 'aircraft noise' you are referring to. This, as you say, functions in a particular way when your dash air con is engaged. I think that is conceivable.

If I was a betting man, I would wager a bet that your mechanical fan clutch is not working correctly (per my original post) and not providing adequate cooling. Your electrical fan provides very limited cooling impact compared to the mechanical fan controlled by the thermal spring/fan clutch. When you hear that kick in (around 200-210), you will know what I am talking about. Temps should rapidly reduce to the stock 195 or thereabouts.

Why don't you leave your dash air con on, get her up to temps and see if the mechanical fan kicks in before you hit 210. You will hear it if it is working. If not, the likelihood is that you have a faulty mechanical fan clutch. The good news is that it is a relatively cheap fix and DIY job if you like that kind of thing.
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Old 09-25-2018, 06:47 PM   #11
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First things first, you need to know what your actual problem is before you try to fix it.
Do some tests with someone else flipping the AC switch inside while you look around at the fans, and see if what you think is happening is actually happening. Both with a cold and hot engine.






Assuming what I think is happening is happening, (your engine electric fan shuts off when the AC turns on) it could also reasonably be that your AC fan and electric fan temp sensor share a ground, and it started getting corroded. When the dash AC fan comes on the current through the bad ground forms a voltage that messes with the temp sensor for the electric fan.
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Old 09-26-2018, 01:05 AM   #12
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You may well have two separate problems;

1) Your dash air con system is not operating as expected:
2) Your Motorhome is overheating.

It's conceivable that they are related, but if you are constantly getting above normal operating temps (200), then you probably have two seperate issues. In my view, I would address any issues with overheating as they will cause costly repairs to the engine and tranny in the long run. For info, dash air con inoperability is probably second only to people's door bells not working on this forum....

Issue 1: The dash air con system is a mix of Airstream and Chevy installed parts. Your coach manual will set out the differences. It's not uncommon for people to mess around with the stock set up and add additional electrical fans to aid cooling, so probably worth establishing whether you are stock or not. If we are referring to the stock set up, I would refer to the following post (94) in the sticky which might help.

http://www.airforums.com/forums/f311...ml#post1895608

This will guide you to the relevant Chevy service, repair and electrical garage manuals, which should set out in detail the correct test procedures for the Chevy installed components of the front air con.

For info - this fella is meant to be good for spare dash parts/knowledge http://soldbyrichard.com/rvacheaterparts.php

Issue 2: If you are regularly getting above normal operating temperatures, you need to establish the underlying cause and, in my view, it's unlikely to be with your dash air con set up. I set out how you can test the mechanical fan clutch which is a common cause of overheating, but there are obviously others. You can find out more on that in service manual links I posted or google the site. Others e.g. Bob and Wayne have upgraded radiators and/or mechanical fans with seemingly good results, so if you find your overheating is not the fan clutch or your dash air con, it would be worth your time reading their posts which might provide some useful information on repairs and fault finding......or just stick it into a good service centre.

I hope this helps.

all the best
Nick
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Old 09-26-2018, 06:58 PM   #13
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All good comments. Thank you. I will do some testing/troubleshooting and share the results. To clarify, this is a recient condition that started 75 miles ago. Prior to that this was not an issue. Thanks again for all the comments.
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Old 10-01-2018, 08:45 AM   #14
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https://photos.app.goo.gl/aqHJxHKpoDs2kRWu7
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Old 10-01-2018, 08:49 AM   #15
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https://photos.app.goo.gl/GfYW9w399TuMEmfE8
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Old 10-01-2018, 09:47 AM   #16
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Old 10-02-2018, 08:38 AM   #17
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https://photos.app.goo.gl/aqHJxHKpoDs2kRWu7
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Old 10-03-2018, 07:11 PM   #18
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Look what I found in 50 pounds of manuals. One of the previous owners either modified or replaced the electric cooling fans wiring system. I haven’t a clue as to what or why this was done. Can anyone venture a guess based on these hand sketches? Any thoughts will be welcome.
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Old 10-04-2018, 04:49 AM   #19
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Look what I found in 50 pounds of manuals. One of the previous owners either modified or replaced the electric cooling fans wiring system. I haven’t a clue as to what or why this was done. Can anyone venture a guess based on these hand sketches? Any thoughts will be welcome.
Why did he do it, who knows. Basically what the PO did was to wire it so that the AC pressure switch, dash switch or engine coolant temp will turn the fans on.

In general that's pretty much what any cooling system with fans is trying to do, turn them on when the temp gets to high or when the AC system is running.

At first glance I don't see why this arrangement wouldn't work. It would be nice to know what coolant sensor was used and what temperature setting causes it's internal switch to close.

Sorry, not much help.

Brad
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Old 10-04-2018, 05:04 AM   #20
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Assuming
1 the coolant temp switch goes to ground
2 the solenoid goes somewhere logical
I also don't see why it wouldn't work

After you troubleshoot and verify what is happening, I'd recommend inspecting all the wiring and looking for bad connections. Also verify that it matches your schematic you just posted. Especially if the PO did the wiring, there could be slice-n-dice connectors gone bad or something.
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