Dash Heat Not working

[Bill C]

I recently found a leak in my dash A/C. It was the low pressure sensor in the front Gen compartment. I'm sure it is a coincident, but after I fixed the freon leak, my dash A/C worked great. I am traveling and needed some dash heat the other day. When I tried it, it never got hot. When I was in the Gen compartment fixing the low press sensor, I did unplug something that could have controlled the dash fan, vacuums, or something, but I plugged it back in and don't think it is the problem, but I just thought I would mention it. 

Anyone know what allows the engine hot coolant to flow in the dash to provide heat?

Thanks for any thoughts.

Bill

[TomV48]

3 hours ago, Bill C said:

I recently found a leak in my dash A/C. It was the low pressure sensor in the front Gen compartment. I'm sure it is a coincident, but after I fixed the freon leak, my dash A/C worked great. I am traveling and needed some dash heat the other day. When I tried it, it never got hot. When I was in the Gen compartment fixing the low press sensor, I did unplug something that could have controlled the dash fan, vacuums, or something, but I plugged it back in and don't think it is the problem, but I just thought I would mention it. 

Anyone know what allows the engine hot coolant to flow in the dash to provide heat?

Thanks for any thoughts.

Bill

I think traditionally, controls in the dash,  actuate a valve in the hot water line from the hot side of the radiator.  In my car and trucks they are on the outside side of the dash/firewall. Usually it is a vacuum control activating a diaphragm that opens the valve.   Sadly or gratefully, I have never had to look at ours in the DP.

[Ivan K]

Do you have a valve like this in your gen compartment?  Ours is on passenger side and controls hot coolant flow to the exchanger.

[Bill C]

Hi Ivan K,

Thank you for posting the info and  image. While mine looks a little different, see pics, your post made me go look a little further, only to find out that the plug I disconnected when working on the low pressure switch, was also the plug that controls my hot water to my dash heater. I don't know if that is the problem yet, but I triple checked, and jiggled it, to make sure there was a good connection there. Tomorrow I will test it. If the dash heat still does not work, at least I know of a good place to check, in case the control valve is faulty. Perhaps the leaking freon shorted this part?

Thanks again.  I noticed that your name comes up a lot on this forum, with helpful information, and I thank your for taking the time to share your knowledge, insight, and experience with the rest of us.

All the Best,

Bill

[Bill C]

Update:

I finally returned to home and took the dash gauges template off 1/2 way yesterday to look for an air leak in the air pressure gauges. When done, I went to work on the dash heat issue, and low and behold, it is working. I had already checked on the wiring going to the HVAC controls, so I don't think that was it. None the less, if the issue comes up again, I will start with the valve in the Gen compartment thanks to Ivan K. I even have the valve model saved in my amazon list, just in case.

Regards,

Bill

[Bill C]

Well, my Dash A/C and Dash heat seem to run at the same time when trying cool. While I have Dash Heat now, it appears that I have Dash Heat in ALL settings, including A/C and Max A/C.

I am planning to replace the coolant control valve, thinking that it is stuck "on", but want to make sure it is not an electrical issue that is letting coolant flow in to the inside heat exchanger all the time (i.e. it is getting 12 volts, opening it up, all the time).

Please see the above pics to see my coolant control valve. 

Below is a pic of my wiring plug that connects to the coolant control valve. Based on measurements, and my wiring diagram, I have made an attempt to label where the wires go/and my readings.

Any insight that you may have would be appreciated.

Also, has anyone replaced a coolant control valve? If so, do I have to worry about a large amount of coolant coming out as I take the old one out, and install the new one?

Thanks in Advance.

Bill

[Ivan K]

Bill, if yours is similar, you may be able to see the motor shaft from a side view. When I was checking ours, I made a sharpie mark on it and watched it turn while DW was turning the dial. If that moves and you still get heat, the flap has likely separated from the shaft. I haven't changed ours but if I did, I would use plugs on the open ports one at a time to minimize the loss. I got a bunch of conical silicone plugs for powder coating but a wine cork would possibly work, just get a case and save them 😃

[Bill C]

Good Advice Ivan K, I'll give it a try when I get to my destination

Thanks,

Bill

[Paul J A]

19 hours ago, Ivan K said:

Bill, if yours is similar, you may be able to see the motor shaft from a side view. When I was checking ours, I made a sharpie mark on it and watched it turn while DW was turning the dial. If that moves and you still get heat, the flap has likely separated from the shaft. I haven't changed ours but if I did, I would use plugs on the open ports one at a time to minimize the loss. I got a bunch of conical silicone plugs for powder coating but a wine cork would possibly work, just get a case and save them 😃

WE do NOT "WHINE" before our time!!!

These guys are terrific on the phone for DASH HVAC issues and parts.  

https://www.comfortairgr.com/

 

[Bill C]

Thanks Paul

[Bill C]

On 10/30/2023 at 6:01 PM, Ivan K said:

Bill, if yours is similar, you may be able to see the motor shaft from a side view. When I was checking ours, I made a sharpie mark on it and watched it turn while DW was turning the dial. If that moves and you still get heat, the flap has likely separated from the shaft. I haven't changed ours but if I did, I would use plugs on the open ports one at a time to minimize the loss. I got a bunch of conical silicone plugs for powder coating but a wine cork would possibly work, just get a case and save them 😃

Update: I purchased a Hot Water Temp control valve thinking that it may be my issue, but unfortunately, I don't think it is the issue. It is hard to see if my existing control valve moves as I change the settings, as Ivan suggested, but I did hook up my new control valve to the  plug that was in my old control valve, and when powered up via the dash controls, I could see the valve move to open the control valve to let water in/out of my dash heat exchanger. Once open, no matter what setting I changed the dash air to, A/C or heat, the control valve remained in the open position, letting hot coolant flow through the dash heat exchanger. 

In looking at my wiring diagram, the next logical (at least to me) culprit seemed like the Position Control Module.

Any thoughts on this? Anyone know where the heck this Position Control module is, or what it looks like?

Thanks,

Bill

[Ivan K]

My control module, which is a little PCB is hanging off the dial/potentiometer on 3 short wires, right behind it. Totally unprotected, may or may not be the same. I had to replace the pot once, when we got it. If I remember right, it was a 5k ohm but I had a 10k in my stash and it worked too. Here is my view from under the dash.

[Bill C]

Thanks Ivan, I will look for it tomorrow.

Any idea if a replacement is available?

[Ivan K]

Bill, look at this link, if the same then they sell the controller at bottom of the page but I would first confirm the pot and wiring. All it does is to compare the reference voltage from the pot to the voltage coming back from the valve.

https://www.thermotion.com/4-port-electronic-heater-control-valve-pn-354-69694

[Bill C]

That's my valve, so must be my module

Thanks

[bgfleck]

Bill,

I've read where some just put a shut off valve on the supply and return leg. Have them off in the summer and on if they traveled in the cooler months.

[Bill C]

Anyone know where I can get this part for my Dash Heat?

Servo Control Circuit Board 305-2537 REV D

[Georgia Mike]

You might try this place to get it repaired 

https://www.acsindustrial.com/repair-catalog/scs/3052547.html

[Bill C]

37 minutes ago, Georgia Mike said:

You might try this place to get it repaired 

https://www.acsindustrial.com/repair-catalog/scs/3052547.html

Tried them they don't work on these

[Ivan K]

On 11/7/2023 at 7:37 PM, Bill C said:

That's my valve, so must be my module

Thanks

So you can't use their module with their valve, if that's where the problem is? I realize the connector would have to be spliced in but it's same count of wires. Assuming the potentiometer checked out?

[Bill C]

It seems that the valve is a diff model, even though it looks the same. With that in mind, I am hesitant to use their position control module, since I have no idea if it will work, and it has diff wiring, how would I match them up properly?