Jump to content

Questions about SCS dash HVAC operation, getting more heat


Recommended Posts

2004 HR Scepter, DP Cummins ISC. Specialty Control Systems on the HVAC enclosure for the two cores. SCS has been "purchased" by Victory Control Systems and did not find any information on their site. Dash AC works very well. Previous Owner installed inline heater shutoff valve in line to heater core, engine side of dash controlled valve. In Colorado last week and needed heat so opened valve. Heat has been marginal at best, except once or twice pretty warm over several weeks.  Engine temp per gauge is in the 180 degF range. Electric actuator for water control valve tracts to hot/cold knob on dash and appears to be opening and closing valve. outside air damper closes on max AC. I did not check outside damper to see if closing on OFF. dash/floor/defrost vents all supply air per setting. fan speed changes per knob, good air flow. Vacuum pump makes a bit of noise but does shut off after engine start and changing air control knob to change damper position. Seemed to run longer at 7,000 ft elevation than at 1,400 ft at Tulsa.

To keep cold air from entering, set to max AC to close outside damper and heat to hot. air exiting dash vents was a bit warmer than inside but just a bit.  Felt hose/manual metal valve going to heater core and it was just warm.  

Plan is to pull heater hoses off valve and heater core and install clear hose to bypass core to see if good coolant flow with engine running. Use low air pressure to confirm flow thru heater core. confirm that valve is actually opening and sealing closed.  Wondering if the manual valve shutting off all flow to the heater core can cause the passages to get blocked?

Something I am not sure about. From the u-tube heater coil replacements I have seen, it appears that the air on these systems flows thru both the evaporator core and then the heater core. I see posts that talk about dampers that seem to be  between the cores. It use to be that the AC compressor ran during defrost to dehumidify the air so the defrost worked better. Does that occur on the SCS system?  Is there a damper that controls flow thru one or the other core?

Have looked at some of the Evans trouble shooting documents. Not sure if their info is basic and the same for the SCS.

Will also see if I can find where coolant lines going to heater core come off and return to block to determine if there are shut off valves at the block.

Any other suggestions on how to get more heat?

Link to comment
Share on other sites

I am on my second Monaco and the heat is marginal at best on both of them. It is not designed to heat that large of an area. I got a couple of small electric heaters and place them so they blow on my feet mainly while driving. 

Link to comment
Share on other sites

I'd say ours is sufficient down to maybe 50 outside and then the aqua hot pumps become necessary even for driver comfort (though we don't need to run the diesel burner). Wonder how well it was burped after the valve was installed. Maybe try burping the hoses to see if you can release an air bubble? 

A/C does run on defrost. 

Edited by trailmug
Link to comment
Share on other sites

Mornin Ken, so after reading your text im reminded of my days working on cars an trucks. On both Chevy and Ford when ever the thermostat is 180 degrees i ALWAYS recieved complaints from owners that the heater must be having a problem because it never got hot coming out of the ducts! Then first thing i would do is to install the required 192 or 195 tstat an that solved there issues. Its going to be intresting this year to see how my coach heater works this year cause i just compleated a major overhaul of my cooling system and my temp gauge went from almost 200 down to 180. Last year when using my heater i had to turn it down cause it was so hot.

Theres possably one more thing to keep in mind, in a sticks an bricks house we wrap the pipes to prevent heat loss, i know for me the amount of hoses are over 30 ft in both directions, perhaps covering the hot side of the hose feeding the heater might be in order. Either way im going to see the effect of my heater operation this winter as well.

Link to comment
Share on other sites

I keep the outside air inlet door permanently closed with a hook at the vacuum actuator. Otherwise it would only close at Max Air setting and AC compressor would run at the same time as heating. Works better for both cooling and heating this way but still need AH at times. Not sure who made our system, pretty complex with vacuum solenoid bank controlling the vacuum actuators.

Link to comment
Share on other sites

good day working on the MH. removed lines from entrance and exit of the inline heater control valve. lost some coolant in the process and air into lines. used two hose barbs and installed 8" long 5/8" clear tubing to replace valve. started up ISC and went to fast idle of 1200 rpm. air bubbles, maybe from air in high spots of line, flowed thru the clear line with pretty good velocity, 6" of clear tube and gone in less than a ~1/4 of a second. water temp in engine up to 140 degF but only maybe 100 coming thru line. reinstalled inline heater valve with clear line at the input. flow thru tubing when dash request hot and pretty much off when on cool. 

I had planned on removing return line off heater core to blow thru with low air pressure but the line is up very high and would have to remove other stuff to get to it. The flow I saw thru the clear tube leads me to believe that the core is not blocked. Tried to find source and return of hoses on engine. looking thru the bedroom access hatch, I found two hoses running along the driver side of engine compartment, on my MH just under the hose that I think contains the dip stick that allows measuring trans fluid level from the rear of the engine compartment. Hoses got warm as engine warmed up. Just above, maybe 4", from the turbo but hose still feels ok. tough to follow hose from that access hatch but I think I found one going into a extension off the engine just under the alternator that I believe is part of the plumbing for engine water going to the radiator. going to take searching from access panel in back closet and underneath to be sure to find it.

Thinking of disconnecting the inline valve and bypassing by installing a barb fitting. will drive the MH enough to get full heat and road rpms to see if any heat. when running on the heat side of the selector switch, I saw the AC compressor kick on/off. When in the vent position on the AC side of the selector, the compressor did not come on when I looked. Only problem with the vent position is the outside air damper is open.

Ivan, I would be interested in how you hooked the damper in the closed position. Do you have issues with the evaporations coil freezing up in humid weather? Have been wondering if a small valve could be installed at the dash to route vacuum to the outside air actuator when needed to close the door. Maybe use a cable that would allow varying the amount of closure. 

Rik, part of the search at the motor is to determine were the supply water comes off with respect to the thermostat. We live in OK and go south were it can be even hotter. I guess in theory, as long as you have enough cooling capacity, it does not mater if the water is in the 180 or 190 degF range when you start doing something that will need more cooling. 

I appreciate the comments. I do not have AquaHot. Told wife about Ken's suggestion of running the electric heaters. She has given me directions to figure out how to make it work, sometimes she has too much faith in my mechanical skills. Her toes were pretty cold last week. I do have a small heater and it is a last resort option.

Link to comment
Share on other sites

So “ok” i keep a stand up 110volt heater in my bedroom so no matter what i keep the bedroom temps even when im plugged into  a CG at night. Otherwise i run the propane heater which has its Highs An lows thru out the night. The highs were A LOT WORSE till i found the sensor wires were tucked up in the cabnit rather than in tbe air sencing port. I had removed the little white vent port off the cabnit an found the sencing tip run up in the cabnit where they struggled to sence ambient air temps. Once i relocated the tips, it was alot better for it to know the room temp.6284768B-CA06-4D1B-9236-4770F65F2E55.thumb.jpeg.96922a5b2b3fd5866f6e2bc7ec3dcac6.jpeg0E6C415A-AB4B-4CA1-9E96-B3658711285E.thumb.jpeg.37394198233e13eab072953e65941960.jpeg

Link to comment
Share on other sites

I installed a switch on the A/C compressor so that I can turn it off when on the heat settings.  I also put a solenoid valve in the vacuum damper system so I can close the outside air damper.  This was to overcome the system design that has the A/C compressor on in all but the vent position.  It also has the outside air damper open in all but the Max A/C position.  Thus, I can set it to recirculate on heat an this helps with the heating.  Both switches are mounted on the dash at the heater control.  The A/C cutoff is easy to install by just cutting into the wire from the heater control.  I have the valve mounted on the firewall for the damper.

Link to comment
Share on other sites

16 minutes ago, Larry Laursen said:

I installed a switch on the A/C compressor so that I can turn it off when on the heat settings.  I also put a solenoid valve in the vacuum damper system so I can close the outside air damper.  This was to overcome the system design that has the A/C compressor on it all but the vent position.  It also has the outside air damper open in all but the Max A/C position.  Thus, I can set it to recirculate on heat an this helps with the heating.  Both switches are mounted on the dash at the heater control.  The A/C cutoff is easy to install by just cutting into the wire from the heater control.  I have the valve mounted on the firewall for the damper.

This, to me, is the ultimate solution. I considered it, got a nice switch to cut into the AC clutch line but then decided to just hold the outside actuator pulled in with a wire hook to keep the damper closed like if it was on Max Air without AC running. Unless I want AC ON and then it recirculates which is what I would do anyway. As a side effect, I don't have outside air venting a live without it just fine.

Link to comment
Share on other sites

Pulled access hatch in rear closet. The two lines I thought went forward to heater do come off the engine block below the alternator. no valves at the block that I could see. The big surprise was that the SCR filter is in one of the hoses. With a manual valve in the heater water line that is shut during the summer, not much water is circulating thru the filter to mix in the SCR. Pulled about 12 oz of existing antifreeze to send off for analysis. Where are people sending there antifreeze and what does it cost 

I have seen pictures of a new style water pump for the ISC from a post were a guy lost his WP seal and was leaking gallons of water. The original design looked like sheet metal formed into the impeller. The new has a "cast" impeller that is said to greatly improve water flow. Anybody changed their's out? Still working on were the heater hoses connect into the coolant passages in the block.

Link to comment
Share on other sites

CB1F9BE2-14AA-4959-AAE4-90CEF1D5E13A.thumb.jpeg.86a4b00f0bda06698908abef1e2b7c89.jpeg4940EE1A-E582-494B-9CBB-8EACBD68D83A.thumb.jpeg.8b7bfa16582bac2507ff0184baa8dd93.jpeg  So this was my WP’s , as far as coolant taps, the OUTLET line is from the back of #6 cylinder head, the SUC side is fro the return line from the tadiator area, lift the bed or? Look down, on the driver side closest behind the fan you will see where a 5/8 hose comming out from there, thats the heater return line

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share

×
×
  • Create New...