dash heater/ac controls

[encantotom]

hi all,

my defrosters have never worked great. so today i had a buddy here for the weekend and we spent a chunk of the day tearing the hole thing down to see what the deal was.

first of all, i had just gotten a like new dash control unit (it is a dodge truck late 80's) and put a new old stock pushbutton and vacuum control unit on it i found on ebay. previously i had replaced the air powered vacuum pump with a 12v ford diesel truck pump. i put the pump in the drivers side bay in front of the wheel.

so the vacuum lines connect with a rubber 7 hole plug that pushes on the back of the control panel and clips hold it on.

the control panels have max ac, ac, heat, vent, defrost.

we took the plenum apart in the front passenger side bay to be able to see the inside where the blower motors are.

we took off all ten flex hoses that come off the plenum. then we put a blow dryer in each of the hoses and traced which vents they sent air too. then i also was able to find out if there was any large volume leaks.

i did find one that seemed to be plugged. that ended up being a hose that was kinked. (fixed)

so now we knew that hoses were are ok.

next we made sure the vacuum source line from the pump to the tank (behind the dash and about the size of a large softball) to the control panel. it worked and held vacuum.

next we used my hand vacuum pump to see which of the remaining two vacuum lines that go from the dash to the plenum do.

one flips between the dash air vents and the defroster vents.

the other opens the two vacuum controlled flappers on the bottom of the plenum on the bottom of the coach that allow fresh air into the plenum.

so we knew they worked and were ok.

btw, i have a aux defroster motor and switch for it on the center console separate than the dash controls.

on the dash, the defroster vents there are ten of them. 5 on each side.

there are two on each side that get hot air from the plenum when switched on. (if the engine is running and the slider is over to hot.

there are two on each side that push air from the aux defroster blower switch on the center console. btw, that takes cabin air, so it is the same temp as the cabin air.

then there is one on each side that are dummy vents. they are purposely blocked off below the dash. because they are in the way of the wipermotor on one side and something else on the other side.

now to try the actual dash controls

we plugged the vacuum plug onto it.

nothing worked.

we took the plug off and after thinking about it for a while we went to the autoparts store and got 1/8" inch vacuum plugs.

it ends up the rubber plug leaked so nothing could work. silcone didnt fix it. it wasnt repairable.

there are 7 ports for the plug. one is the vacuum source and the other 6 are the combinations that have each of the dash control pushbuttons either open up the vacuum port or keep it closed.

we made unions by cutting the end off of the cap and plugged it onto the back of the unit and plugged the 3 vacuum hoses into it and plugged the others so they wouldnt leak.

we knew which one was the source so we use the cut plug as a coupler and put it on the control.

then we experiment with each port to map out which pushbutton setting would open the port.

i wanted fresh air coming in on AC and Vent.

one of the settings only opened the port to vacuum on defrost, so that one went to the defrost hose.

now there were 5 others to check and map.

the closed that we could get this unit to do was to have fresh air on vent and max ac and ac. since my dash air doesnt work very well anyway, that is the one that we used.

then we used our new connection system to hook them up and plug the rest and tried it all out.

now my defrosters work strong and with heat (i ran the engine to get the coolant up to temp).

the louvers open to fresh air on the right settings.

and all works again.

btw, it wasnt hooked up that way for vacuum lines before. so now it is the way that i wanted.

another little thing fixed.

fun way to spend a saturday after a stressful work week.

tom

[HoosierDaddy]

Thanks Tom I've been starting to figure mine out. So far I dont have heat up front. I opened the two coolant valves on the engine to no avail. I'm assuming there must be a coolant pump to push hot coolant to the front. I need to check that out next.

[encantotom]

hi dean,

there are many different configs on the coolant lines from the engine to the front. (on 8v92's anyway)

some have two valves at the back, most have 4. the ones with two have one set that usually just control the inlet and outlet to the hot water heater.

mine only has two. as it comes off the engine, it goes to a solenoid controlled pump mounted on top of the frame rail right in plain site in the drivers side engine compartment. the solenoid opens the valve AND turns on the pump at the same time. it pushes coolant up towards the front.

in the middle of the coach in the ceiling of the bays, you will find a maze of coolant hoses. they are a series of Y's and i check mine once in a while to make sure the hose clamps are tight.

on mine, i have a heater core under the bed with a fan that is controlled by a switch on the dash. there is also a heater core in the drivers side wet bay with a fan that is turned on by a switch on the dash.

i also have my hot water heater fed from it as well as the heater core up front.

the y's enable a return path for the coolant even if any one line is turned off or plugged. my hot water heater didnt work initially and i found that the return and inlet coolant lines had been reversed at some point. when i switched them back it worked great. in fact too great in that it was too hot so i put a tempering valve in.

unlike any others i have found, i also have a solenoid controlled pump at the front to push the coolant back to the radiator. it turns on at the same time as the one in the rear.

both pumps and valves are controlled by turning the heat lever on the dash heater/ac control towards heat. newell installed a microswitch on the lever mechanism that turns it on after it is barely moved to the right. if you listen while moving the lever with nothing on in the coach you can hear the microswitch click when it hits the turn on point.

to get hot water from my hot water heater from coolant, i have to have the lever turned on. the problem is that the same lever opens the slide valve with a cable that opens the water to the heater core up front and your vents get warm.

when i put my new control unit on i transplanted the microswitch from the old one and tried to make it so it was barely on when it turns the switch on. sometimes i want hot water when i dont want hot air...like when it is not cold out.

some people have solenoid controlled valves at the bed heater core or bay heater core. if my pump is on, those two heater cores on mine get hot. if the fan switch is not on, it is not blowing hot air.

the front pump that i found is behind the plenum behind the front cap and you can only see it if you get a few of the plenum hoses off. that is also where the slide valve is that is actuated by the boden cable that runs from the lever control on the dash.

i drew a map of my hoses but since each one is different, you will have to do that for yourself.

btw, the vent hoses are lightweight flex hose and are getting brittle with age. i have had to seal up leaks on a few of mine.

hope that helps some. call me if you want me to talk through it.

tom

[folivier]

Tom, how hot does your dash heater get?
Mine is just warm, not enough to even keep my little toesies warm on a cold day. I have 4 valves on engine, heater under the bed, and in water bay.
I added a valve on each of the coolant lines under the bed to keep it from getting hot. Even with the heater switch off I found that it heated up the bedroom.
But the dash heat is not nearly as hot as the heater under the bed.
Great investigation tracking down your problem.

[encantotom]

mine gets fairly warm. i will run it to temp some time this week (just sitting in the driveway), and measure the temps.

tom

[77newell]

Tom, how hot does your dash heater get?
Mine is just warm, not enough to even keep my little toesies warm on a cold day. I have 4 valves on engine, heater under the bed, and in water bay.
I added a valve on each of the coolant lines under the bed to keep it from getting hot. Even with the heater switch off I found that it heated up the bedroom.
But the dash heat is not nearly as hot as the heater under the bed.
Great investigation tracking down your problem.

I own Forests "old" coach mentioned by him in this quote. The configuration as I preliminarily understand it is that this coach has two circuits; one with a boost pump and solenoid valve that feeds the front heat, and one without a boost pump that feeds the heater under the rear bed and the water heater coil. I have yet to figure out which circuit serves the bay heater. There are two shutoff valves on the engine water pump output and two shutoff valves on downstream of the engine thermostat above the water pump.

After a short trip this week I will be exploring what is going on in the front since my crude heating system in the 77 coach put out far more heat that this 93 does. I would have thought that newer coaches should heat better than the older ones and I intend to get it there. The way the heat performs now there is no way I could avoid frostbite when traveling in below freezing temps without wearing my snowmobile gear which would appear garish in a Newell.

My boost pump is making grinding noises and will have to be replaced - does anyone have information on a replacement.

[Neweller]

Jon, I have replaced a couple of these booster pumps over the years and I had put a MP-100 on one of my Newell's to pump up to the front heater. At one time I had a few extras but think they are long gone by now. I was selling them for about half of the ones on this site. You may find the exact match here. Let us know if any of these match yours?

.: TAC :. Transportation Accessories Company (http://commerce1.cera.net/tacbusparts/sections/catalog/catalog.asp?cat_id=155)



MP-100 Example: 4447

[NewellCrazy]

Jon,

your '93 should have one set of valves (the lowest two valves on the side of the engine) are for the front heater. There is an inline booster pump for this circuit which is activated when the temperature control lever for the dash heat is turned about 1/2" off of cold. The valve that is the outgoing line is on the bottom. The other two valves are higher up with the top most valve actually on the front on the engine. Those lines circulate water to the rear bedroom heater and the water heater.

Also does your coach have the primus system?

Just sharing some info,

Sean

[77newell]

Sean: I have two two lines running up the inside of the right frame rail and two other lines running up the inside of the left frame rail. I assumed that each side constituted a single circuit. One hose in each circuit connects to one of the lower shutoff valves and the other hose in each circuit connects to one of the upper valves. Where I could go wrong in my assumption is if one of the hoses crosses over to the opposing side somewhere forward of the rear axle where I haven't gone yet. Each of the hoses running up the right frame rail are tapped off for the under-bed heater.

Your configuration could well be different but this is how my coach is plumbed.

Ken: I used the same company as a source for the boost pump I installed on my 77 coach which seemed to never have had one, but thanks for the reminder. The pump made a substantial improvement in heating output.

You two guys are always a great source of help and I appreciate you both.