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Old 09-08-2020, 09:50 AM   #1
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Electrical issue for dash air and heater fan

While on vacation in July we started having the dash air fan shut off meaning no air from air conditioner. It might shut off and come right back on or be off until it decides to come back on.
When the fan quits it won't come back on if you switch to vent or heat suggesting to me that the power to the fan controller is losing power. I have replaced the fan control speed switch. when the fan works I have all three speeds for fan.
Some days I can switch it on and it works perfectly and other days it won't work at all.
When the fan is dead I have jumpered the fan switch with 12 volt power and fan worked.
The wiring diagrams that I have found don't show where the power source comes from that supplies power to the switch.
The Motorhome is a 2004 Georgetown 370. The dash air blows cold when it works.
Anyone have any suggestions?
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Old 09-08-2020, 01:37 PM   #2
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Don't know what your selector panels look like. If there are different fan speeds that can be selected are all the speeds affected?
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Old 09-08-2020, 01:43 PM   #3
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It Doesn't matter which speed I put it on they either work or don't work. I have low, med, and high speeds. When it shuts down nothing works either on air or heat. Changing any setting on the controls has no effect. When it is dead it won't restart until it decides to or I jumper the fan speed control {Switch} with a 12 power {Jumper}taken from a live 12 volt power source.
when I start the engine the air conditioner might work but at any time it might quit and only restart when it wants to. The same with the heater.
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Old 09-08-2020, 01:44 PM   #4
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Here is a schematic for the F53 HVAC system. The 2nd and 3rd views may be applicable to your unit. They are to my 2012 GT378. I know it doesn't help with the source of power but may be of some use. The resistive unit is installed in the air plenum inside the coach on the co-pilot side. Might check for the connections on the back of the panels for looseness.
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Old 09-08-2020, 01:52 PM   #5
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According to your owners manual (2004 F53 motorhome chassis) the blower motor relay fuse is #7 in the fuse panel to the left of the steering column on the floor. and the relay is #5 in the power distribution box in the engine compartment (under the hood).
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Old 09-08-2020, 03:03 PM   #6
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Check power to the compressor clutch when on.
You can also check if someone inside turns on AC and OFF.
Should hear a click at the compressor when it it engaged.
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Old 09-08-2020, 07:20 PM   #7
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Quote:
Originally Posted by Iggy View Post
Check power to the compressor clutch when on.
You can also check if someone inside turns on AC and OFF.
Should hear a click at the compressor when it it engaged.
He said the fan didn't work in vent/heat modes also.
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Old 09-08-2020, 08:54 PM   #8
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Thank you bubbles for your reply and the schematic for the F53 HVAC system. This schematic is much better then what I have been able to find on the internet.
I am looking for a possible bad connection at the ignition switch ? going to the fuse block under the hood as I found 10 volts but can't get it to do it now. Now it is reading 12 plus volts at the 40 amp fuse. That is fuse 23 that supplies voltage to the fan motor. This has me scratching my head. Batteries have a full charge and checking voltage shows 12.5 to 13.5 volts.
I also am looking for a bad ground I may need to focus on this more.
I have ruled out a bad fuse as it does work sometimes. Not sure about the relay. I can swap it out easy enough. Could a relay switch off and on like I am having?
I also have almost ruled out the resistor for the blower motor. My understanding is if the resistor is bad it will still work on high only. Since I have all 3 speeds it seems like the resistor is good. I will keep this in mind if I can't find anything else.
Something I haven't checked is vacuum mode switch. I am not even sure how to check this other then checking for voltage at the wires when the blower is working.
My motorhome is back at the storage lot. With the new schematic that you have supplied I'll try getting down there tomorrow to check everything.
Thanks again for your information.
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Old 09-09-2020, 07:25 AM   #9
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In my 2012 GT the steering wheel (column) accessories exit the steering column near the floor via 2 connectors. As said the HVAC dwg does replicate my 2012 GT but don't know about your 2004 GT. Don't know where the grounds would be but perhaps your coach has a similar multi ground termination point such as this and one of them might be bad. It's just a wag.
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Old 09-09-2020, 08:44 AM   #10
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This is another dwg that may assist. Just shootin in the dark here and not sure it is applicable to your coach.
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Old 09-09-2020, 09:00 AM   #11
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You need to check for power and ground at the fan blower motor when it is not working. Check all speeds. I would say 99% of the time power and ground are good and the brushes in the fan motor are worn out. If you are missing either back track the wiring diagram.
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Old 09-09-2020, 01:23 PM   #12
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Hasty decision

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I have ruled out a bad fuse as it does work sometimes.
That was a hasty decision. Twice on my personal vehicles I have had a fuse fail with a hairline crack that repeatedly healed when power was removed and reapplied. The crack was apparently vibration-induced.

The most memorable time was in my 1970 Opel GT. The fuse that supplied the radio and wipers would work fine with the radio on or the wipers on, but if you turned on both, it would open and not conduct until the ignition was turned off. I had inspected it and it appeared complete--although I ignored the fact that the metallic strip was bent in a V, right in the center.

As I crawled upside-down under the dash one evening, back-and-butt on the seat, head on the floor, and feet in the air, I happened to pass my worklight behind the fuse. And that's when I saw the light--literally, light was passing through the hairline crack at the bottom of the V.

And if you think that's hard to find, just wait until you have a fuse strip which detaches from the metal end cap where you can't see it.
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Old 09-09-2020, 11:06 PM   #13
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I spent 2 hours checking the circuit for the air conditioner. I started the engine up and the blower started blowing cold air. The whole time I was there when the engine was running the blower was blowing cold air. I know it isn't fixed but waiting until I need it so it can quit.
I checked and cleaned one ground, tightened another, swapped out number 5 relay and looked for anything that might not be right. I have the dash pulled apart and the controls for the air conditioner / heater are pulled so I can get to them.
I have noticed one thing that I hadn't paid attention to before. The blower switch has 4 positions on it shown by dots . I assume that the smallest dot is supposed to be off and each larger dot is for a faster speed. The largest dot I assume is for high speed.
What I have is the smallest dot is low, next is med. then the next is high with the largest dot being off. Nothing says off on the fan switch only dots. It has been this way since I have owned the motorhome, {almost 4 years}. I do know that someone worked on the air conditioner and replaced the compressor while the last owner had it. For almost 4 years I haven't had any problems with the air / heat until this summer.
I am running out of ideas.
We are leaving on the 18 for a weekend camping trip with family, and then we are planing on being on the road several more days to take in some site seeing.
As far as getting under the dash to check those fuses I will have to pull the drivers seat as my back won't bend enough to get under the dash with my rear on the seat. I am too old for that. I will swap out the two fuses I know that operate the air conditioner. I will try to post a pictures of the heater controls tomorrow.
Thanks for everyone's replies. I'll be going to do some more checking over the weekend.
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Old 09-10-2020, 06:23 AM   #14
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With the fan speed set to the lowest setting (off) when a mode is selected (vent/A/C/ etc.) the fan should still come on at a low speed and then can be increased. That's the way mine works.
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Old 09-10-2020, 08:38 AM   #15
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High speed

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With the fan speed set to the lowest setting (off) when a mode is selected (vent/A/C/ etc.) the fan should still come on at a low speed and then can be increased. That's the way mine works.
Given that, the switch positions should all progressively increase the speed.

Just as a data point, a 1995 Chevrolet Lumina APV I had was built with peculiar circuitry for the blower. All the low speeds went through one relay, but the highest speed went through another that completely bypassed the series resistor. I never analyzed why it was designed that way, but when the top-speed relay burned out (bad connector), all but the highest speed continued to work.

Wondering if there's a second relay involved...
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Old 09-10-2020, 09:03 AM   #16
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No second relay in my GT. All blower speeds controlled via resistor network. All resistors are just bypassed (see post #4 for schematic, page 2, of resistor network) for speed control.
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Old 09-10-2020, 03:03 PM   #17
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Pulled the passenger seat out and got under the dash. I checked the fan motor carefully but couldn't find the resistor pack for the speed control of the blower motor. I pulled the blower motor part way out to check behind the motor and couldn't find any wires or anything that would lead me to believe there was a resistor pack inside the blower housing.
I tried to follow the two wires coming from the blower and could only follow them back about a foot and then they disappeared in a tight area under the dash.
If anyone knows where the resistor pack is let me know as I can't find it.
I believe the main powered wire inside the resistor pack is defective allowing the lower speeds to operate, but shutting off the high speed. This might account for the blower to shut off and turn back on by itself.
I'll be spending more time on it this weekend but Friday is taken.
I will post if I ever find what it is. Thanks for everyones help.
Three pictures if they show up show the air / heat controls from the front and top view and a picture of the fan motor. The hose at the top wasn't attached when I first looked at the motor. Click image for larger version

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Old 09-10-2020, 03:59 PM   #18
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In the ductwork

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If anyone knows where the resistor pack is let me know as I can't find it.

I believe the main powered wire inside the resistor pack is defective allowing the lower speeds to operate, but shutting off the high speed. This might account for the blower to shut off and turn back on by itself.

I'll be spending more time on it this weekend but Friday is taken.

I will post if I ever find what it is. Thanks for everyone's help.
The resistor is always inside the ductwork. It gets very hot. Putting it there keeps it from damaging anything, adds a little heat in the winter while the engine is warming up, and is in the flow of warm air used to modulate the degree of coolness in the summer.
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Old 09-10-2020, 05:03 PM   #19
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Larry-NC I have looked at all the ductwork that can be seen. The next thing is to start pulling the dash apart where the back up monitor, radio, gen start and one blower vent are located. This can be done easy enough as I have had this apart before. If you can't see it from there I don't have any other ideas. I was hoping someone with a 2004 or 5 might have replaced the resistor before and knew where it is located. Very hard to follow the wires as they disappear in the tight area under the dash.
What I read it is usually close to the blower to keep it cool, but what I found today is the resistor isn't anywhere close to the blower that I can see.
It might be Sunday before I get back down to the storage lot.
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Old 09-10-2020, 07:01 PM   #20
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As said in my 2012 GT the resistor network is in the bottom of the distribution plenum inside on the copilot side up under the dash. Sorry for the blurry picture. Yours may also be there.
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