1983 MC9 - Ex NJT - Coach heat MIA

plyonsMC9 · November 23, 2015, 09:17:40 AM

Thanks very much Ted.

IF I'm testing correctly, I have _no_ current when bus is off, powered on w/Low air, powered on and fully aired up, and when I turn on the bus heat switch for the coach. I haven't tested when the engine is fully warmed up though.

My point of test is the ground terminal (neg) near the main water valve, and the terminal on the side of the valve (pos).

Does my testing methodology seem correct? My tester only has 10v DC and 50v DC. I tried both settings trying to get any movement out of the needle, but nada.

Kind Regards, Phil

TedCalvert · November 24, 2015, 02:19:33 PM

Sorry I didn't get back sooner.

I take it that your meter is an analog meter that has two voltage ranges: 0-10 and 0-50. If that's the case, leave it on the 50-volt range for testing voltage. Make sure that it's set for DC, not AC. Verify that it works by putting it directly on the battery. Nothing is worse than chasing a problem on wrong readings.

Furthermore, I understand that your solenoid valve only has one terminal, and that the other end of the coil is somehow internally connected to the body of the valve and therefore, hopefully, completing the circuit back to the battery through the vehicle's body/frame (ground).

If all that's correct, then yes, you're on the right track to determine if the coil is powered or not. But we don't know if the coil should be powered, or not, when calling for heat.

Maybe you should think about possibly rigging a bypass line around the valve for testing? That's a PITA. Are you sure the system is not air-blocked? My Prevost has a bleed valve off the top of the driver's core. Depends on how the coach is sitting, too.

Good luck; keep us posted.

plyonsMC9 · November 24, 2015, 07:02:22 PM

Thanks for the response Ted. I'll read it a few times to make sure I copy all that you are saying. I'll test out my analog meter on the battery. Great idea. Also, am pretty sure we're not air blocked. I did open the valve on the driver's heater core. Also had a diesel mechanic friend of mine do the same - each time we did that, as soon as the valve was opened, coolant came immediately out. Coach is setting on a level, concrete slab.

Also, I'm going to test to determine whether I've lost my ground, and I'll post back here.

Kind Regards, Phil

luvrbus · November 25, 2015, 01:54:16 AM

Phil, the valve operates with 10v min to 15v max so don't going looking for 24v,the diaphragm is probably bad those are supposed to be replaced every year according to the MCI maintenance program

plyonsMC9 · November 25, 2015, 08:56:52 AM

Hi Ted,
My analog meter seems to test OK when testing against the battery, it shows a little under 28v - approx.

Testing the negative terminal/connector on the suspect valve to the bus ground looks like the ground connection is strong.

Hi Clifford,
Testing positive connector @ 10vdc on my tester still shows no current whatsover at the valve. Clifford, do you know whether these fail open, or closed? I'm ordering the diaphragm through Luke right now.

My valve markings:
Valve - sol.opr.
P.N. 36830062
25PSI - 24VDC

Thanks all very much! Phil

gumpy · November 28, 2015, 10:56:48 AM

Quote from: luvrbus on November 25, 2015, 01:54:16 AM
Phil, the valve operates with 10v min to 15v max so don't going looking for 24v,the diaphragm is probably bad those are supposed to be replaced every year according to the MCI maintenance program

MC9 is 24v. Only 12v relay in them is the blower relay in the rear panel. Valve is 24v.

I'm suspicious of the gate valve in the rear. The stem on one of mine broke and I had to replace the valve.

I'm also suspicious of the relay. You should swap it with one from that toad converter you bought just to make sure it's not the relay.

There's also a sensing unit in the air tunnel, front bay, left side, by the A/C junction box. That's what sends the signal to the relay.
If changing the relay doesn't do anything, test for voltage on the coil terminals and on the output terminals. You could jumper the coil terminals with
some alligator clips to see if you get heat. If you do, it may be the bulb sensor in the tunnel.

By the way, the photo you posted of the valve is the return valve. The supply valve is up in the center above the transmission.

luvrbus · November 28, 2015, 11:20:23 AM

I think you will find NJT MCI 9's are 10 to 15v on that valve I could be wrong but I have chased that problem on the NJT 9's before

gumpy · November 29, 2015, 01:25:39 AM

Quote from: luvrbus on November 28, 2015, 11:20:23 AM
I think you will find NJT MCI 9's are 10 to 15v on that valve I could be wrong but I have chased that problem on the NJT 9's before

That would be surprising, but maybe they did something different there just for NJT.

Normal MC9 schematic has 24v going through the 12v discharge and blower cut-in relay to rear stud 2 to feed front stud 30 and then terminals 1, 8, and 7 on the
coach heat relay. From terminal 1, it goes out through terminal 3 when relay is activated to front terminal 43 to AC j-box stud 7, and then to water valve.
The heat relay is activated by the mercury switch sensing unit in the tunnel closing and grounding the coil on the relay at terminal 2.

The schematic says the water valve is normally open.

luvrbus · November 29, 2015, 01:44:57 AM

A lot of things on NJT MCI's are different,I ran across 1 with a DDEC 1 engine that was straight 12 v with a air starter they did that because the DDEC 1 is 12 V only they have their own manuals and it changes with serial numbers, of the 1100 or so NJT Mci 9's you don't see many for some reason
NJT did some weird stuff like the Eagle was a 12V system they used a 24v air and heating system with a air starter then every wire was white in color with a tag you couldn't read.Gary Hatt the owner of this board has a NJT MCI 9 moose cabin also

Boomer · November 29, 2015, 07:28:51 AM

As suggested, the NJT buses were odd ducks. We owned quite a few MC-9's and as I recall any HVAC problems dealt with A/C, not heat. If both water valves in the engine compartment are open you should have hot water to the cores. Not to say there is not some kind of restriction in the pipes, or perhaps a total failure of the electric water valve but we never saw it happen. The thermo bulb reads the temp of the return air in the tunnel and depending on how the temp reostat is set will open and close the water valve by grounding it. You don't need a volt tester on that valve, it's either working or not and can test with a probe. I would check your gate valves or maybe put a kit in the electric water valve, I don't think the problem is electrical unless it's a NJT thing. JMO

plyonsMC9 · November 29, 2015, 09:40:19 AM

Greeting!

Thanks very much to all for the suggestions. I'm working on this as time away from my day job permits.

I'll swap relays with that from toad converter sometime in the next week or so - great idea. Thanks Craig.

Re: photo, I did check heat around the supply gate valve as well but didn't snap a picture of it. Pipes around supply gate were also hot for a couple feet around both sides of the the valve going up & down the pipe. I didn't check past a couple of feet going forward as I couldn't easily reach the pipe. If it's a recommended troubleshooting step to go past a couple of feet towards the front of the bus along the supply coolant pipe, I'll figure out a way to do so.

Diaphragm rebuild rubber arrived from Luke @ US Coach. I need to figure out how replace that w/o a huge mess.

Is there any kind of pump to move the coolant around the heater cores & pipes that I need to be concerned with, or is all the coolant for the heating system moved by the engine system itself? I don't show any extra pumps in my manuals from 1989, but checking to be sure.

Kind Regards, Phil

gumpy · November 29, 2015, 02:01:16 PM

Quote from: plyonsMC9 on November 29, 2015, 09:40:19 AM
Greeting!

Thanks very much to all for the suggestions. I'm working on this as time away from my day job permits.

I'll swap relays with that from toad converter sometime in the next week or so - great idea. Thanks Craig.

Re: photo, I did check heat around the supply gate valve as well but didn't snap a picture of it. Pipes around supply gate were also hot for a couple feet around both sides of the the valve going up & down the pipe. I didn't check past a couple of feet going forward as I couldn't easily reach the pipe. If it's a recommended troubleshooting step to go past a couple of feet towards the front of the bus along the supply coolant pipe, I'll figure out a way to do so.

Diaphragm rebuild rubber arrived from Luke @ US Coach. I need to figure out how replace that w/o a huge mess.

Is there any kind of pump to move the coolant around the heater cores & pipes that I need to be concerned with, or is all the coolant for the heating system moved by the engine system itself? I don't show any extra pumps in my manuals from 1989, but checking to be sure.

Kind Regards, Phil

On a normal MC9, there are no auxiliary pumps to move the coolant. All coolant pumping is done by the engine water pump. Evidently you can't count on the normal with an NJT.

Opening the valve shouldn't be a huge mess, but you need to shut off the 2 valves in the rear or it will become a mess when it drains the radiators. Shut those valves, and
also shut the driver's heat valve by the electrical panel. Then you should be able to break the line with minimal coolant loss (1-2 gallons from the lines in the tunnel).
The valve is above the heater core, so not much concern about that. Use a bucket to catch what comes out.

plyons · December 01, 2015, 08:03:01 AM

Arrrgh. OK, that makes sense, thanks Craig. But it does look like before I work on the valve I'll need to first fix the rear supply valve which is stuck in the open position. Don't know when I've had more fun...

Will swap out relays next week.

Kind Regards, Phil

gumpy · December 01, 2015, 01:59:20 PM

Quote from: plyons on December 01, 2015, 08:03:01 AM
Arrrgh. OK, that makes sense, thanks Craig. But it does look like before I work on the valve I'll need to first fix the rear supply valve which is stuck in the open position. Don't know when I've had more fun...

Will swap out relays next week.

Kind Regards, Phil

Oh, wait. Your supply valve is stuck in the open position? How do you know that?

You may well have just found your missing heat problem. It's possible the gate is closed and the shaft is broken.

If you think it's just stuck, run the bus and heat it up. Then try the valve. The heat may unstick it.

That valve is a real pain to replace. It's soldered in place. I had to pretty much lay on my belly on the floor and solder the new one in using the upside down braille
sweat solder technique. You'll need to drain down the entire coolant system to replace it.

plyons · December 01, 2015, 06:18:02 PM

Hi Craig,

Here's how I _think_ I know it's stuck open. As long as I've owned the bus (over 10 years now) - that valve has been stuck. Back to when the heat used to work amazingly well. During summer I would just close off the driver side valve and the return valve.

I don't think I've tried to turn the supply valve with the bus heat up tho'. Pretty sure I always turn the vales with the bus cool. I will give that a shot.

After the torture you describe in replacing that valve, I'm really, really, really hoping the relay is bad.

Thanks Craig, Phil