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This is anaecdotal and may have nothing to do with your problem………

My first coach had a similar issue relating to intermittent driver’s blower operation and the culprit turned out to be the fan relay that on that particular coach was in the drivers side electrical compartment.

[Rudy]

Could it be the temp sensor for the dash air? A faulty sensor could be sending erratic signals to the fan by demanding more or less air to control the temp.

[Davy]

Based on research and phone calls today there is not another relay in the system.

Jon’s suggestion is a good one but the tickle to engage the blower has been moved to an enclosed clear epoxy sealed heat sink pack. This is controlled by the touch pad on the dash control. a signal is sent to this sealed relay box .mounted inside the air exchanger with the blower.

Tom’s suggestion on the temp sensor I learned controls degrees of air temp and not blower speed increase or decrease.

Prevost search of wiring diagrams shows no other control modules, boards, relays in blower system.

Making a long story short there is only one other electrical unit, that being dash control box. So after lunch I ordered the dash control.

Interesting the original has been superseded by an up dated model and this unit includes a wiring change adapter for my existing control. Sales on dash control box about 20 some every 6 months.

Cost….$793, shipping is free

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BA, Merry Xmas. Isn’t it nice that shipping is free on a 8000 part that’s probably worth between 500 and 1000. Geo.

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I have no idea how this odd ball stuff gets attached to me.

You know the dam blower speed goes up and down and how could this be any more then a speed regulator ? At $180

It’s fixed and on to something else. Nope

My problem still exists so it’s determined that the blower assembly manufactured in 1996 has probably a bad motor. At $473 its new replacement will run smooth and quiet and we’re done. Nope,

More digging and what’s left but the dash controller at $793.

Here we go we all love push button products but do we want parts bills totaling $1446 dollars.

Merry Christmas everyone !

[Tim]

I hope so. Aggravating(sp) If not run a new groung to black wire going to motors also the relay block attached to bottom of dash frame. right of brake pedal about a foot is bad about loosing ground. I had mine loose during rebuild of dash and things didn’t work. Put screws back in and all was good. Maybe I’m late to game but just read this. I pay less than 150 for non prevost defroster/heat/ac (motors in front air box). Just two wires going to 24 volt motors that are pulling 12 V on low 18 volt on med and 24 v on high thru reostat/fan control. Bob

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Robert ,

I have my e-mail open.

Could we talk by phone about ground wires and locations ?

AL

I might have found my problem….. which wire do you want me to look at ?

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Com-On Man. Now AL thats not a Marathon….

[glen]

As with some things, when it rains it pours. Dash control box arrived with includes 1)dash push button control box. 2) wiring extenders about 10 inches long. 3) heat sensor with about 12 inch extender with double spade plug in.

Prevost says this is just a plug and play retro kit. I like this so what could possibly go wrong. I notice the dash control box has the last two numbers different then mine. I pay some attention to this check the box number to the parts list, it’s same number but determine its retro stuff so they have changed the dash box to a new part number. Exam the other parts which according to the instructions say I must remount the temp sensor from the defroster box after removing the drivers dash cover. Drill a 1 inch hole in the air exchanger box on the pass side, route a 3/4 inch rubber tube from this hole across the dash and mount under the driver side dash. Drill holes to use furnished mounts for permanent placement. Under the drivers dash mount the new temp sensor in the furnished plastic holder along with hose end.

Problems; the air box mount is slightly to big and hits dash panel when closed.

I’am wondering why heat sensor is mounted under the dash now as the location is not exactly drawn the same as my under dash.

Heat sensor plug end has 2 spade terminals and the dash box has 4 female much smaller. This new sensor wiring is not going to be plug and play.

Call Jeff he locates the detailed instructions IS-00093, 5 pages for this retro change over step by step. Learn I must cut into the wiring harness to abandon wire 29H out of one plug in. It also fails to mention any thing about sensor plug in with 2 entirely different ends. I’am thinking this is where the 2 wire sensor connects into the harness.

I cannot find wire 29 H in the harness but do find wires 2941, 29H3,29H4.

Calling it a day I watch the KC Chiefs football game. Monday morning call Nashville Prevost and speak to Richard Jackson parts specialist. Give him bus serial number and we go through the order again. Spending about 1/2 hour checking. Close to his lunch hour he asks to call me back.

Richard said the same thing as Jeff….this sounds like a grounding problem. Richard also tells me these dash control boxes are known for causing strange things to happen with A/C -Heat systems in there operation, and has heard of the on-off blower motor which I’am trying to correct. He also asked if any dash lights come on when the blower starts ? No lights have flickered ever during blower run. Richard is fairly certain the dash box replacement will correct this blower problem. That was good to hear.

Phone rings, it’s Richard, “I think I’ve found your problem”. You have a retro kit for a small A/C system. What you need is a replacement for a large A/C system. Richard say’s it came to me at lunch that you told me you had OTR air.

Yes, and that kit is for a bus with only dash air bus. Give me the number on the parts bag, and give me the number on the customer order pick slip. They DO NOT match,

So bottom line the parts in the bag are wrong, the number on the bag is for a different A/C system and the parts picker DID NOT pull the right part number.

That folks is the tri – fecta of a parts screw up.

So RGN on the parts I have and the correct dash box shows available in Jacksonville and will be shipped today.

This repair is not finished….. but I want to thank Jeff for helping me and Richard Jackson at Prevost Nashville that started from the beginning checking bus number against part numbers.

AL

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The above message is long and involved and most of all frustrating.

The dash AC / Heat system is fixed and preforms better then the original installed parts back in 2000. I have learned a lot.

Thanks to Mike Frezel at Prevost – Nashville who by his long Prevost employment helped me the most, Finding someone who has done this upgrade was a huge assist. Example, told me there is a second plug in behind the dash in the wire loom after an hour and a half found it. This is the attachment for new sensor.

Ran the entire button system on dash box twice before putting dash back together. Yesterday the big road test. Worked better then before., quiet and heat continuous not the past experience where heat slowly decreases then fires back up.

Old and new control, new part numbers and 2 plug Ins attached to dash box which plug into existing. Looks easy but finding room for new wiring was an issue. Tags on new box warn user not to disconnect plug on above. Mike F. also warned me of the same. Doing so will blow new box when you press the “on” button with engine running.

New sensor in-between boxes.

Dark picture new box is under radio (silver box) wiring runs on back side to dash top.

New relocated sensor mounted under dash above drivers right leg. Clear tube runs back to air box.

Clear tube mounted on dash air box — air is forced into tube with blower running. Center of photo 9 o clock. New blower and regulator are inside air box.

Parts total…..drum roll, $16410 includes Prevost free shipping.

[Jimmy]

robertglines1 posted he was buying the fan motor for 1500

for front hvac.

he doesn’t have email authorized so I hope he will read and post info or someone friends will contact him. My phone number is 919 252 7220

gmjdw@yahoo.com

[Roy]

gmjdw

I tried the number posted with no success.

AL

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The number is correct for my cell

919 252 7220