Mystery A/C prob & idle surges - ThreePoints

Johnny K · 07-04-2010, 04:11 AM

94 E320 Wagon, My awesome little white wagon has problems and I need help !!

The idle most of the time will surge up to 1100-1200 RPM and then down to under 400 RPM, this causes the car to stall out sometimes. This happens when at higher speeds too. It feels like the car is cutting out, yes sometimes it will stall while moving.

The other problem is this: The A/C will blow heat when the temp dial is on cold and it will blow cold when the temp. dial is on heat. I have found that to get A/C on cold I can put a ground to the left side pole on the mono valve.That is one of two poles that have a plug that conects to it and it is the one closest to the passenger. This is OK now but I need heat and actual control later in the year.
A little help please.
Johnny K
Edmonton, Canada

94 E320 Wagon (Whitey)
89 300 SE (right hand drive) only 75,000 KM (Righty)
86 300 SDL (Cecil the Diesel)
93 Daughter that names my cars !!

ArmchairExpert · 07-07-2010, 02:30 AM

It's most likely a vacuum issue which can cause both problems. Either a vacuum leak or one of the vacuum elements under the dash that open and close the system doors has gone bad.
The manual with the procedure or a drawing of your vacuum lines and a Mityvac will be needed to check this. The lines going to all the elements is under the dash on the passenger side at a single manifolt/switch. Checking is a logical procedure following the lines from source (engine) to the elements.

Vacuum elements control which doors are open to the heater core and evaporator, blending them to get the temp dialed. With elements not working, whether bad or just not getting vacuum when they should, they give you hot all the time (default for failure is warm defrost). Grounding the monovalve shuts off the flow of hot coolant to the heater core so ambient temp air comes through the failed door. Maybe someone can describe it better, but your blending hot and cold air until the vacuum issue is resolved.

Johnny K · 08-18-2010, 08:17 PM

Thanks Armchair, An air mass sender solved the surging. Next is the A/C

John

ArmchairExpert · 08-18-2010, 08:44 PM

Glad you got the surging fixed!
Now the fun part. My Main Air Flap Vacuum Element (some people call them "Pods") has quit. It was easy to diagnose, but it's not going to be fun removing the dash. Been driving my Cherokee during the heat wave because I'm lazy.
I have some links to DIYs with photos if you need them.
I hope this isn't a social faux pas - they're from a different forum.

PeachPartsWiki: Dashboard Replacement
PeachPartsWiki: Center Vent Pod Replacement

Johnny K · 08-19-2010, 01:19 AM

Thanks Armchair, I will look these over , will keep updating

Johnny K

ArmchairExpert · 08-19-2010, 01:54 AM

If you get a Mityvac, or a $19 brass version from Harbor Freight, you can check for vacuum leaks at the manifold under the dash, on the passenger side, almost behind the section above the console where the controls are. Pull them one at a time and see if they all hold vacuum. If not, you get to pull the dash!
I'm replacing all of mine. I figure after 18 years if one failed this year, next year will be another. So, all new rubber, one time diving in. I'd rather swap an engine.

Johnny K · 08-19-2010, 07:02 AM

Hi Armchair, those are both good ideas, have you sourced out the pods yet?
I get a daily e-mail from Harbor freight so I will order one next week, thanks again

Johnny K

ArmchairExpert · 08-19-2010, 01:33 PM

After shopping around I ordered them from Parts Geek. The price was about the same at PartsBin. Rusty and others were significantly more. I've never seen any brand except Behr, so there's no off brand that will save a few dollars. Strangely every online store lists the Vacuum Elements under "Body Mechanical and Trim", not under "Climate Control". The door lock elements are listed in the same category.
There is a vacuum check valve you may need, $7.95. But they usually don't quit working.
I'm out of town next week so may attack it first week of September. I can't skip it until next year as I now have 42F air out of my heater ducts and only get heat through the Defroster.

Johnny K · 08-20-2010, 02:38 AM

Quote:

Originally Posted by ArmchairExpert

After shopping around I ordered them from Parts Geek. The price was about the same at PartsBin. Rusty and others were significantly more. I've never seen any brand except Behr, so there's no off brand that will save a few dollars. Strangely every online store lists the Vacuum Elements under "Body Mechanical and Trim", not under "Climate Control". The door lock elements are listed in the same category.
There is a vacuum check valve you may need, $7.95. But they usually don't quit working.
I'm out of town next week so may attack it first week of September. I can't skip it until next year as I now have 42F air out of my heater ducts and only get heat through the Defroster.

Thanks Armchair

John

Johnny K · 08-20-2010, 02:49 AM

Quote:

Originally Posted by Johnny K

Thanks Armchair

John

Hey Armchair, how many of the elements are needed and is there any other stuff needed?

Thanks,

Johnny K

07-04-2010, 04:11 AM	#1
Johnny K Johnny K Join Date: Jun 2010 Location: Edmonton, Alberta Posts: 12	Mystery A/C prob & idle surges 94 E320 Wagon, My awesome little white wagon has problems and I need help !! The idle most of the time will surge up to 1100-1200 RPM and then down to under 400 RPM, this causes the car to stall out sometimes. This happens when at higher speeds too. It feels like the car is cutting out, yes sometimes it will stall while moving. The other problem is this: The A/C will blow heat when the temp dial is on cold and it will blow cold when the temp. dial is on heat. I have found that to get A/C on cold I can put a ground to the left side pole on the mono valve.That is one of two poles that have a plug that conects to it and it is the one closest to the passenger. This is OK now but I need heat and actual control later in the year. A little help please. Johnny K Edmonton, Canada 94 E320 Wagon (Whitey) 89 300 SE (right hand drive) only 75,000 KM (Righty) 86 300 SDL (Cecil the Diesel) 93 Daughter that names my cars !!

07-07-2010, 02:30 AM	#2
ArmchairExpert Plank Owner Join Date: Jun 2010 Location: DC, Maryland Posts: 31	It's most likely a vacuum issue which can cause both problems. Either a vacuum leak or one of the vacuum elements under the dash that open and close the system doors has gone bad. The manual with the procedure or a drawing of your vacuum lines and a Mityvac will be needed to check this. The lines going to all the elements is under the dash on the passenger side at a single manifolt/switch. Checking is a logical procedure following the lines from source (engine) to the elements. Vacuum elements control which doors are open to the heater core and evaporator, blending them to get the temp dialed. With elements not working, whether bad or just not getting vacuum when they should, they give you hot all the time (default for failure is warm defrost). Grounding the monovalve shuts off the flow of hot coolant to the heater core so ambient temp air comes through the failed door. Maybe someone can describe it better, but your blending hot and cold air until the vacuum issue is resolved. __________________ 1992 300D 2.5 Turbo Last edited by ArmchairExpert; 07-07-2010 at 03:14 AM.

08-18-2010, 08:17 PM	#3
Johnny K Johnny K Join Date: Jun 2010 Location: Edmonton, Alberta Posts: 12	Surge problem solved Thanks Armchair, An air mass sender solved the surging. Next is the A/C John

08-18-2010, 08:44 PM	#4
ArmchairExpert Plank Owner Join Date: Jun 2010 Location: DC, Maryland Posts: 31	Glad you got the surging fixed! Now the fun part. My Main Air Flap Vacuum Element (some people call them "Pods") has quit. It was easy to diagnose, but it's not going to be fun removing the dash. Been driving my Cherokee during the heat wave because I'm lazy. I have some links to DIYs with photos if you need them. I hope this isn't a social faux pas - they're from a different forum. PeachPartsWiki: Dashboard Replacement PeachPartsWiki: Center Vent Pod Replacement __________________ 1992 300D 2.5 Turbo

08-19-2010, 01:19 AM	#5
Johnny K Johnny K Join Date: Jun 2010 Location: Edmonton, Alberta Posts: 12	Pod pics Thanks Armchair, I will look these over , will keep updating Johnny K

08-19-2010, 01:54 AM	#6
ArmchairExpert Plank Owner Join Date: Jun 2010 Location: DC, Maryland Posts: 31	If you get a Mityvac, or a $19 brass version from Harbor Freight, you can check for vacuum leaks at the manifold under the dash, on the passenger side, almost behind the section above the console where the controls are. Pull them one at a time and see if they all hold vacuum. If not, you get to pull the dash! I'm replacing all of mine. I figure after 18 years if one failed this year, next year will be another. So, all new rubber, one time diving in. I'd rather swap an engine. __________________ 1992 300D 2.5 Turbo

08-19-2010, 07:02 AM	#7
Johnny K Johnny K Join Date: Jun 2010 Location: Edmonton, Alberta Posts: 12	MIghty Vac Hi Armchair, those are both good ideas, have you sourced out the pods yet? I get a daily e-mail from Harbor freight so I will order one next week, thanks again Johnny K

08-19-2010, 01:33 PM	#8
ArmchairExpert Plank Owner Join Date: Jun 2010 Location: DC, Maryland Posts: 31	After shopping around I ordered them from Parts Geek. The price was about the same at PartsBin. Rusty and others were significantly more. I've never seen any brand except Behr, so there's no off brand that will save a few dollars. Strangely every online store lists the Vacuum Elements under "Body Mechanical and Trim", not under "Climate Control". The door lock elements are listed in the same category. There is a vacuum check valve you may need, $7.95. But they usually don't quit working. I'm out of town next week so may attack it first week of September. I can't skip it until next year as I now have 42F air out of my heater ducts and only get heat through the Defroster. __________________ 1992 300D 2.5 Turbo

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