Dash AC Condensor Fan Wiring

[talgutbir]

Hi All,

I have a 2009 Mandalay 40 and having a problem with the condenser fan at the back of the motorhome. I didn't have good cooling from the dash AC and traced it to the fan wires at the back (after connecting gauges and verify good charge).

Someone routed the harness close to the exhaust and melted the wires. I tested the fan by providing 12V direct and it works fine. The harness that provide power to the fan runs towards the front but it is in the middle of the coach with a bunch of other wires so I can't see where it goes.

I would like to know if anyone knows where the relay (if it activated by one) is, or where to go from here??

Thanks.

[wolfe10]

talgutbir,

Welcome to the FMCA Forum.

Your chassis maker (? Freightliner?) should be able to provide you with the wiring schematics for that circuit.

If Freightliner, give them a call with your VIN: 800 385-4357

[talgutbir]

Thanks! I wasn't sure if Freightliner installed it or the coach manufacturer. I will contact them to see if they can help.

[dickandlois]

talgutbir,

Welcome to the forum!

The AC system is installed by the Coach builder. When you activate the AC system the evaporator fan is powered by a harness installed by Freightliner along with The 3 fuses in the chassis harness. a 20, 25 and 30 amp. there is also a fusible link installed by Freightliner along with a relay. The fusible link supplies the 12 volts that powers the evaporator fan circuit. (This wiring layout is quite common on coach dash AC systems).

The fact that the evaporator fan runs when you apply power to the motor and the wires have been compromised by the exhaust heat and there are no blown fuses, would indeed lead one to suspect a blown FL (fusible link)

The Frightliner wiring for your chassis has numbers printed on each wire, So if you can find the numbers - copy them down. Like 1652- 4 digits long in most cases.

Like Brett mentioned, contact Freightliner with the last 6 numbers of the Vin Code. Ask for a PDF copy of the Chassis electrical wiring.

Not knowing your back ground in reading electrical drawings- you might have the ability to trace these wires to where they originate. Also, you might want to ask where they mount the evaporator fan relay and where to find the fusible link.

FYI it should be connected to a primary 12 volt supply point, but where it would be in this case is the big question.

With out the cooling fan running, the high pressure switch opens - this in turn disengages the magnetic clutch on the Compressor. This action would allow for very little cooling, but you might get some.

Rich.

The system is most likely supplied by DENSO

[talgutbir]

Rich,

Thanks for the help. I emailed Freightliner, so see what comes back. You say there are 3 fuses but I couldn't find any?? The unit works fine when I use a water hose over the condenser to keep the high pressure down and the clutch is working on the compressor. I do get a good 25 degree difference between ambient and duct temp, junt can't get the fan to run while connected to the harness.

[dickandlois]

Rich,

Thanks for the help. I emailed Freightliner, so see what comes back. You say there are 3 fuses but I couldn't find any?? The unit works fine when I use a water hose over the condenser to keep the high pressure down and the clutch is working on the compressor. I do get a good 25 degree difference between ambient and duct temp, junt can't get the fan to run while connected to the harness.

The fact that you get good cooling with water flowing over the evaporator leaves the lack of 12 volts to the fan as the key.

Good work-never thought about hosing down the evaporator ! A new trick to add to my file!

Do you have the owners manual? Does it list the fuse panel fuses and the circuit related to them?

The fuse sizes are common, the primary fuse is the 30 amp. Then the 25 and or 20 amp fuses power different portions of the system. servo system and blower motor.

The 30 amp fuse powers the fan circuit in question on many systems, but all of your system works accept the cooling fan. SO it sure sounds like a blow FL.

Exhaust pipes make for good grounds and heat melts insulation.

I need to see if by chance I have any wiring info. for the Mandalay on file. The coach-I know that there are no drawings for the 09 chassis on file.

05 model is the closest model on file- Fuse # 31 is listed as the Condenser fuse and is rated at 25 amps. Fuse panel is located under the cover just in front of the steering column.

Rich.

Oh, look for some numbers on the wires if you get time!

[talgutbir]

The fuse box doesn't list any fuse for AC. Freightliner just replied that the coach builder is the one that wired the ac unit. I thought that the fan is connected together with the compressor clutch and should come on when the clutch engages. Since the clutch works I assume that the fuse (or lack of one) is fine.

I have the Mandalay manual but there are no wiring diagrams in it. If you find something let me know.

Thanks,

Tal

[dickandlois]

Tal,

The coach builders do not include wiring drawings in the owners manuals, but they often do picture the chassis fuse panels and the coach panels in the electrical section.

Freightliner just replied that the coach builder is the one that wired the ac unit.

This is correct, but the key here is that they supply coach builder circuits from the chassis wiring to supply power to the dash heater and AC system. Also the power steps and accessory outlets.

The interesting thing is that the chassis fuse panel and fuse are listed in and older model owners manual.

This includes the fuse for the Blower motor and system servo board and the fuse for the AC evaporator fan.

Did Freightliner supply you with the PDF chassis wiring drawings for your Vin. number chassis?

I could PM my email info so you can forward a copy that I could look over if you wish..

Another thought - Did frightliner install the evaporator and cooling fan before shipping the chassis. To be truthful, my feeling is NO.

Because of the damage to the wiring harness and if the wires used for the fan circuit are not numbered. Then they did not build the circuit into the chassis harness.

That leaves the coach builder!!!

Rich.

[talgutbir]

Rich,

I found the fuse panel under the dash but can't find a burned fuse. I contacted Thor to see if they can give me a diagram since the fuses are marked (i.e. F1, F2 etc).

here is the Freightliner email:

"Tal,

Freightliner installs the ac compressor condensor fan, etc. We do not supply the power for this, the Body Builder Four Winds supplys power thru all the dash a/c system. If they have a relay or fuse you would need to contact them for the location. Their number is toll free 877-500-1020."

I also got a PDF with the wiring diagram for the compressor clutch with the email from them.

I will PM you.

[dickandlois]

Tal,

Thanks for the update.

Hope Thor supplies some useful information. Now, if they do not have a fuse location and size, ask if they used a fusible link and where they placed it.

Because coach builders change things around from year to year and model to model and at times change suppliers to keep the assembly lines running makes for a challenge tying things together.

Rich.

[talgutbir]

Still nothing from Thor but Rich saved the day with the PDF file! Found the bad fuse....

[jleamont]

Next step....why the open fuse? High resistance in the fan motor? Chafed harness?

Perhaps try and shake the wiring around while the fan is running (keep your fingers, hands and loose clothing away from any moving parts), look for chafe points where the wires pass through.