Author Topic: Dash heat/AC/Fan quit working  (Read 6935 times)

Rick Vyncke

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Dash heat/AC/Fan quit working
« on: June 17, 2016, 03:27:53 AM »
2004 Beaver Marquis

Last weekend I removed the dash cluster so that I could run an RCA cable to the stereo to display Aladdin info on my new TV.  While that was a success.... the heater control book away (seems it was glued to back of dash).  Didn't have time to fix then and that was going to be this weekend's project. 

While taking the coach to the park for this weekend's heater panel reinstallation the dash air and fan quit working.  I can't help but wonder if it being loose in the dash allowed a power wire to make contact a blow a fuse.  Problem is I have no idea where the fuse for the dash heater/AC/fan is.  If you can point me in the right direction I would appreciate it.

Wishing I lived near BCS  :-[
Rick V
2004 Beaver Marquis, Garnet (3 slides)
43'
C12

steve zannella

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Re: Dash heat/AC/Fan quit working
« Reply #1 on: June 17, 2016, 03:55:54 AM »
Rick

The dash A/C blower and condenser fan are connected to a thermal breaker that trips when over heated and resets when cool. The beaker is located on the 12 volt switched power bar in the front drivers side electrical bay.

You should have an electrical schematic glued to the inside of the electrical bay door, look for A/C.

David T. Richelderfer

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Re: Dash heat/AC/Fan quit working
« Reply #2 on: September 26, 2016, 10:42:40 PM »
I am having the same problem as Rick had - no power to the dash fan/heat/ac head on the right side of the gauges on the dashboard.  I have checked both buss bars in the electrical power bay.  The left buss bar has 13.7v from top to bottom and every wire connected to it has power.  The right ignition-activated buss bar has 13.7 v from top to bottom and every wire connected to it has power.  On the ignition-activated buss bar the 5th wire from the bottom is labeled a/c on the door's schematic.  That "a/c" label is the closest description I see on the schematic that pertains to the dash fan/heat/ac head.  None of the Hella relay descriptions on the door's schematic appear to have anything to do with the dash fan/heat/ac operation.  But I am thinking at least one of the Hella relays should be involved.  All the other stuff related to the dash - all lights, Aladdin, Silverleaf, etc. - are working fine that I know of.

Sooo... somewhere after the ignition buss bar and before the dash fan/heat/ac head on the dash board there is a break in continuity.  It could be a Hella relay because I do not know how to check them, nor do I know which relay might be the one to check.  There are about 25 Hella relays on the wall left side of the left buss bar.

Does someone know if one or more of those Hella relays are involved in providing power to the dash fan/heat/ac head?

Does someone know if there is a fuse between the electrical power bay and the dash fan/heat/ac head - perhaps behind the dash board?

Any other suggestions for where to look?
« Last Edit: September 27, 2016, 05:42:32 PM by David T. Richelderfer »
2004 Beaver Marquis Sapphire

I had a dream... then I lived it!

David T. Richelderfer

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Re: Dash heat/AC/Fan quit working
« Reply #3 on: October 02, 2016, 02:08:27 AM »
I am still digging.  I talked to Rick Vyncke about his problem.  He discovered the next time he used his fan/heat/ac head unit that it worked.  But after running his air conditioning for 20 minutes or so it would kick out for a while and turn on again.  My guess is he has something going on with the air conditioning devices where they are pulling too much power and overheating the thermal breaker in the power bay.  My problem is different, at least, the symptoms are different.

I checked the six wires going into an 8-pin Delphi connector behind the dash leading to the back of the fan speed knob.  One wire is hot, 13.6v.  I checked the same lead coming out of the Delphi connector before and after it splits - 13.6v on both wires after the split.  This is all with the fan speed knob in the off position.  Immediately when I turn on the fan speed knob the hot wire loses power.  How can that be?

The dash fan/heat/ac head that sits in the dash is readily available on the internet, part number 16233143, and is a commonly used GM part from the late 1990s to early 2000s.  The part cost is from $130 to $185.  But as Mr. Farris continuously states, paraphrasing - "Don't throw parts at the problem.  That can get expensive.  Properly diagnose the problem and replace only the part/s that is/are bad."

What is the next step to diagnose this problem?
« Last Edit: October 02, 2016, 02:11:34 AM by David T. Richelderfer »
2004 Beaver Marquis Sapphire

I had a dream... then I lived it!

Edward Buker

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Re: Dash heat/AC/Fan quit working
« Reply #4 on: October 02, 2016, 04:38:51 AM »
David,

If you have a resistive wire path (near break in wire, bad contact in a plug) you will get full voltage when there is no current load. The reason for this is without current flow through the resistive path there is no voltage drop. When you add the fan load the resistive path in the wire now drops the voltage and the fan will not operate.

As an example, last week I was working on my new dash air compressor. When I got it up and running I found that my condenser fan was not operating. I measured 11.5V at the fan leads with no load and no charging source and so I thought the fan was bad. Changed the fan out and had the same issue. So I ran a a temporary 12V + wire and it powered the fan fine. The repair was to come from the electrical bay to the fan with a new wire. When I got around to measuring the original wire path it was 44ohms, should have been .2 ohms.

Try a temporary lead from the electrical bay to the 13V wire that is the power source wire that you measured on the fan control head. If you could find a schematic somewhere that shows which wire is the 12V feed that would be best. It does not have to be an RV schematic.

The temporary test lead should come off one of the thermal breakers on the output end for test purposes. If that works then you need to do some digging to find out what the control knob switch for the fan is rated at for current. If it will handle 20 amps then you do not need a relay. You may find a schematic for older GM vehicles that used that control head and see how it was wired. I am thinking it was direct wired without any relay given all the fan speed positions and resistors involved. It would be good to know how this is wired to sort it all out. Hope this helps.

Later Ed

Edward Buker

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Re: Dash heat/AC/Fan quit working
« Reply #5 on: October 02, 2016, 01:12:18 PM »
David,

There is a schematic in this link that shows the switch, the external resistor pack, the motor, and a relay that is switched to on in the high position. The 12V comes in and on the three fan lower speeds (lo, S1,S2 positions) the resistors are tapped and added in series with the motor . The high position is a separate circuit using a relay feed through a fuse. If none of the positions work it is either the 12V feed wire (brown in the diagram) or the blower motor is bad, or the relay is bad (not too likely given it feeds power on two different contacts depending on the switch position but still possible) or the ground connection is bad.

The fuse is only involved in the high position so if no position works it is not the fuse. If you have an old car headlight with a couple of wire feeds on it you could attach one wire to to the 12V feed of the fan control coming in from the coach chassis wiring and touch the other headlight wire to a ground. If it lights, the power coming in is good. If not you need to sort that feed wire problem out or replace it.

If it does light I would pull the motor next to test it or unplug the wire feed while in place and try and supply an alternate 12 V and a ground wire to it and see if it runs.

Study the schematic diagram a bit and run these tests and you should be able to sort out what is bad. The resistor pack in mine is behind the bumper, looks like some coils. The relay is most likely in the electrical bay, smaller chance that it is mounted near the switch or motor. Hope this helps and good luck.

http://www.silveradosierra.com/how-to-articles/how-to-repair-gmc-ck-series-trucks-hvac-control-unit-t77522.html

Later Ed

Joe DeWeese

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Re: Dash heat/AC/Fan quit working
« Reply #6 on: April 24, 2018, 12:58:58 AM »
2006 Beaver Monterey. Dash air fan was working when we put it in storage in Jan.  Now the fan doesn’t work on any speed setting.  I pulled the connector off of the dash fan speed switch and measured the voltage on all four pins: no voltage on any of the pins.  I expected one to have 12 v.  I checked all of the relays in the electrical Bay, all appear to be okay.  I have no idea how to get to the dash fan itself.  Any ideas in what to do next, don’t want to be roasting driving across western US going to Bend in July. Thanks
Joe DeWeese

Gerald Farris

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Re: Dash heat/AC/Fan quit working
« Reply #7 on: April 24, 2018, 01:48:40 AM »
Joe,
There is no way to tell where you are losing power at without taking a meter and running the circuit, but since it is all blower speeds that are inop, I would start at the master switch on your A/C control panel.

Gerald 

Steve Huber Co-Admin

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Re: Dash heat/AC/Fan quit working
« Reply #8 on: April 24, 2018, 04:50:55 PM »
Joe,
Also check the fan resistor. It should be located on the front firewall. It looks like a coil and probably has a guard over it as it can get very hot. I don't think the fan is the problem if you are not getting power to the switch when you've selected a fan speed.
Steve
Steve
2015-          07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Joe DeWeese

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Re: Dash heat/AC/Fan quit working
« Reply #9 on: April 25, 2018, 09:33:38 PM »
Found and fixed the problem, finally!!  I had to take the front dash apart to get access to the fan motor.  Then I discovered that the power connector on the fan motor had come off completely.  The plastic catch on the connector doesn’t work, electrical taped it back on.  Funny what you find in these coaches.  There was a whole piece of finish plywood just floating around inside the front dash space, complete with 4-5 Kreg cuts in it, not connected to anything.  Anyway we now have dash air and I know how to disassemble the front dash
     Thanks for all of your help and support.  It kept me going when I was getting frustrated.

Larry C Perdue

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Re: Dash heat/AC/Fan quit working
« Reply #10 on: April 29, 2018, 11:49:20 PM »
I had the run awhile, stop awhile problem with my 1999 Monterey. Finally took it to a good local A/C shop. Both heat and A/C were involved. They pulled a vacuum control module, cleaned and lubricated it, and returned it...works fine since that. Thermo King in Roanoke, Va.