MAN HTR light

[Cheezewhiz]

Hey folks, I've got a 1995 thomas west coast er.

Recently the MAN HTR warning light on the dash has popped on, and stays on as long as the keys are in it.

Any of y'all know what it's for? Nothing seems wrong at all

[Rucker]

sorry, no idea.

[cadillackid]

its your grid heater for when its cold.. but i thought only came on when the keys were turned on to the run position.. 'MANifold 'HeaTeR'.. wierd that its on anytime the keys are in the ignition..

[Albatross]

possible sensor or relay out on it.
I'd figure out what triggers that system to come on, and then work backwards from there.

[Wuzabus]

Hey Cheezewhiz. I know when I had my 96 Thomas RE in SC when I drove...they told us NOT TO DRIVE IT with that orange main heater light if it stayed on after we started it up. I have no idea why but I I'll reach out to one of the mechanics from the barn and see what I can find out.

[Jolly Roger bus 223]

its your glow plug relay or your glow plugs burnt out not heating up?

[Cheezewhiz]

Well ****.

Yeah, i'd greatly appreciate the reasoning there.

No glow plugs, so I don't have to worry about those screwing up.

[Wuzabus]

Ok from what was relayed to me just now cheeze it's is your intake heater he believes. He asked me to send a picture of the light on the dash to be sure since it's been like 10 years since he's worked on the rear engine. I didn't know SC did away with the rear engine Thomas and went back to the C2. He's committed to helping you all he can!

[Cheezewhiz]

That's the guy. Next to the stop engine light.

And hell yeah, awesome! Definitely interested in any insight, especially from folks familiar with these.


I found a couple bits on other forums confirming it is an intake manifold heater. which, other than excessive power draw for no reason once it's started, doesn't strike me as particularly problematic.

Extra heat in summer conditions isn't ideal of course, but I'm freezing my tits off right now so...


Merp on pic being sideways

[cadillackid]

I mentioned it before.. its a manifold heater. and it may very well operate during summer too... engine starting summer or winter can be improved with extra heat.. the glowplugs operate on my 7.3 in the summer just not as long... the manifold (intake) heaters operate on DT466E and cummins 5.9 in summer too for the first start of the day..


it shouldnt however operate when just the key is IN, it should operate when the key is ON..



most of these older ones on non electronic engines have a temp sensor and a timer... if the intake is already a certain temp it wont come on at all... if its warm enough it will come on until the timer expires or the sensor reaches temp then it goes off.


these heat the air in the manifold and not the cylinders directly.. so you dont need (or want) to wait for the light to go off.. you can give it a few seconds to start warming up then start the engine.. it will continue to heat the air while the engne is cranking.. if you get a no start and the ight goes off then you cycle the key off and back on and the timer resets. glowplugs on the other hand have a wait-to-start function so that the plug is hot enough to ignite the fuel as soon as it enters the cylinder thus why you wait before cranking.. in most glow-plug engnes the glowplugs do stay on after the light goes out and some of them stay on after the engine starts...


on pre electronic engines the manifold heater will stay on afyer engine starts until its temp is rached or timer expires... it wont hurt anything..


do be Very careful using ether on an engine with a manifold heater... the ether can ignite in the intake manifold or in the piping around the heater and make a bad day for you..



on a glowplug engine ether can ignite too early create really high cylinder pressures for an instant (not good)...

[Albatross]

Just a consideration, if it's an extra heater on the intake, then perhaps you should consider buying and using one of those shrouds that cover half the radiator in this kind of weather. Those are used to keep more of the heat produced by then engine inside the engine, since diesels need that heat in order to operate correctly.



This seems like it might solve the problem that you're having, since it seems like a potential issue here is that you're operating the bus in temperatures colder than it was actually designed for--and that nothing is in fact wrong with the engine, the sensors, or anything else.


Hell, you could even try zip-tying some kind of plywood or plastic over the lower half of the radiator to see if that might fix the issue, and watch to see if the light goes off.

[sportyrick]

If a glow plug relay sticks and melts the ends off of glow plugs and ruins the engine what about intake heater, if that relay sticks can't it melt down and get ingested into the engine? being interested in how an intake heater works I put power to my extra C7 heater and watched it get hot, I could see where if it stuck on it could melt, sounds serious to me.

[s2mikon]

And NEVER spray ether in one of those. I'v seen the damage.