RE: a 1984 300D. I'm not getting any heat in this vehicle. Can someone list the things to look for? I know for a fact that the mono-valve was replaced, what else is there? A faulty button-box??? Actually, how do you test for a faulty mono-valve? I think you apply 12V to it? Is that right? Thanks.

Unplug the monovalve. It closes with 12 volts so unplugged it should give you full heat. Also, pull it out and look it. The rubber diaphragm should be intact.

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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13

The very first thing is to remove the monovalve plunger and see if it is not torn. Anything else is speculative until this is confirmed.

I have been down the no heat road with a brand new monovalve repair kit. The plunger would intermittantly stick in the monovalve body. I found the problem by bench testing it. Remove it from the car and very carefully wire it up so you can apply and remove power from a battery or other 12 volt power source. You should be able to blow air through it with no voltage applied, and it should seal completely when voltage it applied.

BTW, the taste of that 20 year old plastic is extremely nasty.

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

Great... Just took mine for a spin, and I have no heat either... I get some "ram air" heat from the center vent, but nothing from the sides that I can control with the blower control. I turn it onto cool, and it blows air. I turn it to heat, no blower action.

Could this be a broken monovalve? How do you fix that?
~Nate

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95 Honda Shadow ACE 1100.
1999 Plymouth Neon Expresso. 2.4 swap, 10.5 to 1 comp, big cams. Autocross time attack vehicle!
2012 Escape, 'hunter" (5 sp 4cyl)

If you're getting no blower action at a particular setting that might be a problem with the CCU itself. If the blower worked properly and you just didn't have any heat at all, I'd say that might be a monovalve but the blower cutting out at a particular setting might be a problem with the blower itself or the CCU.

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Seth

1984 300D 225K
1985 300D Donor body
1985 300D Turbo 165K. Totaled. Donor Engine. It runs!!!
1980 300SD 311K My New Baby.
1979 BMW 633csi 62K+++? Dead odo

I recommend not eating your 300D.

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"That f***in' biodiesel is makin' me hungry."

1982 300TD Astral Silver w/ 250k (BIO BNZ)
2001 Aprilia SR50 Corsa Red w/ 5.5k (>100 MPG)

I can't be as bad as blowing through the fuel filter to see if it's clogged.

Yes it can!!

__________________
Palangi

2004 C240 Wagon 203.261 Baby Benz
2008 ML320 CDI Highway Cruiser
2006 Toyota Prius, Saving the Planet @ 48 mpg
2000 F-150, Destroying the Planet @ 20 mpg



TRUMP .......... WHITEHOUSE
HILLARY .........JAILHOUSE
BERNIE .......... NUTHOUSE
0BAMA .......... OUTHOUSE

What he said.
Even if it was installed last week.
New parts that go bad are very common.