I'll try to be brief. For the last year or so I've been plagued with an ongoing problem involving my climate control. Two trips to a Mercedes mechanic with a good reputation have proven fruitless. Within the last month or so my "Check Engin" light started glowing. I had a friend (a former mechanic, now a bus driver) check it out for me and the code came back 1700 in memory (whatever that means). Something to do with the transmission, so he "adjusted the control pressure cable". That took care of the "check engin" light for about a week and then it came back on, but now my climate control has resumed working perfectly. This seems too "cause and effect" to be mere coincidence. Any opinions?

It is possible that they could be related. your check engine light code of p1700 is a fault with the upshift delay system of the transmission. Upshift delay is when you start the car cold, it holds shifts longer to heat up the catalyst. It does this by applying vacuum to the control cable which has a vacuum pod attatched, and vacuum holds the cable to delay the shifts. these vacuum pods leak after time and this is possibly why you are getting a check engine light on.

Your climate control system is also vacuum operated, so if there is a vacuum leak, it would affect your climate control system with all sorts of weird problems.

What kind of MB do you have?

Thanks for the reply. It sounds like you might be onto something. My car is a 95 C280. I forgot to mention that delayed shifting feature has been greatly reduced. Previously I needed to go several city blocks before it would shift up, but now it shifts after a block or so. Any suggestions as to my next move?

Well it sounds like we're getting there. First, go to the module box on the passenger side of engine compartment near the windshield and lift up the cover. There is a vacuum switch-over valve that controls the upshift delay and it has a green vacuum line that comes out of the valve and goes across the firewall and down to the trans. Take the green vacuum line off at the switch and test it with a vacuum pump and see if the vacuum pod leaks, it probably does. If so you will need to replaced the entire cable assy as the vacuum pod is not available seperate. Also check the other vacuum line going to the switchover valve(I think it's black/grey?) and make sure you have vacuum present(it is the feed), if not follow the line to the engine and make sure it's connected and not cracked/broken along the way. Your car has a vacuum block in the same module box area which is a junction block that feeds the locks, climate control, etc.. and these leak sometimes. There is also a vacuum reservoir that sits behind the passenger side fender that cracks sometimes giving a bad vacuum leak. Hope this helps, good luck.

Great! One more question about the vacuum pump. FastLane doesn't have the part (or is out), but Autozone has what they call a bleeder/vacuum pump for my model at about $30.00. Is this what I need, and is it's operation intuative? Thanks.

Ok guys here’s a strange question. Three weeks ago our ‘94 C220 (100,000 Km) refused to start. It turned over just fine… just wouldn’t fire up. Next day it was fine. No “Check Engine” light. Two weeks ago same problem.

Flatbedded it to the MB Dealer. Wouldn’t start when it was unloaded so the techs pushed it into the service bay –whereupon it would start!

They hooked it up to their diagnostic equip. and couldn’t find anything wrong. So… I loaned it to the service advisor for a week to see if he had any problems.

A week later he phoned saying they were stumped. Car ran just fine… although he mentioned the heater/AC fan seemed to be “surging”. Probably “blower regulator”.

Last Friday “Check Engine” light came on - but the car seemed to run Ok. I took it to the MB Dealer on Monday for a code download and clear.

They performed the following tests:
541011 - Short test
271210 - Delayed upshift system
801290 – Pneumatic test – Manifold vacuum assist

The service advisor said “No shorts detected”, “No vacuum leaks detected” and that it needed an “Upshift delay cable”. He presented me with a repair estimate of $524.50 (+ tax) and a bill for $185.73 for diagnostics. He wouldn’t say what the OBDII code was and didn’t clear the memory.

On the way home I stopped into the local “Independent” garage (who does all of the maintenance on my Jeep) to see what they had to say. They hooked up their generic “SnapOn” scanner, obtained an error code P1700 (unknown fault), cleared the memory and sent me on my way 10 minutes later – NO CHARGE!

A search of this site for “P1700” shows a thread “Mysterious Check Engin/Climate Control conection”

Seeing as my Heater/AC fan is surging and I have a P1700 code is it possible they are connected – even though the dealer says “No vacuum leaks detected”?

What should I do to verify?

Would this P1700 problem be related to why the car would intermittently refuse to start?

Are these repair and diagnostic costs reasonable?

Isn’t there somebody out there who has come across a similar situation??

Hi, Bensaddict,

Where is the vacuum switch-over valve? I found two green lines in the location you said. Would you please let me know if it's #1 in the right hand side of the picture below or #2 near the lower left corner? Thanks.

__________________
Harry (94 C280)

first thing to replace is the vacuum distributor block in lower left of your picture.it is cheap and you can use a small open ended wrench to pop off the connections without damage.[common prob with these cars].

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

Robert,

Did this ever get resolved?

I've been having a similar problem on my '97 C230. The A/C matter has just cropped up, with airflow from the center vents cut when I accelerate and resuming when I ease off the gas. The transmission, too, has intermittently been sticking in 2nd -- almost, as you describe, like an extreme version of the upshift delay designed in for when the car is cold (except that my tranny problem almost always happens when the car is warm). So instead of my upshift delay being greatly reduced, as you describe, it has (at random times) been greatly enhanced.

Could this *also* be a vacuum problem? Anybody have an idea?
.

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

Anybody?

I just spoke to my regular mechanic, and he seemed to feel that my car, having the electronic 722.6 tranny, would *not* use vacuum to work the upshift or delay. Certainly the code I've gotten indicates nothing about vacuum issues, just the controller/solenoid stuff.

Too much to hope for, I guess, that one overall vacuum repair would solve both of my current problems?
.

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino

the airflow going away when you hit gas suggests that centre vent vac pod leaks.just saw same thing in same year car 3 days ago.unfortunately dash has to come off for replacement.

__________________
David S Poole
European Performance
Dallas, TX
4696880422

"Fortune favors the prepared mind"
1987 Mercedes Benz 420SEL
1988 Mercedes Benz 300TE (With new evaporator)
2000 Mercedes Benz C280
http://www.w108.org/gallery/albums/A...1159.thumb.jpg

Thanks, David,

My regular guy says that the pod or system to check and replace is actually under the hood, as in Hancheng's post above. True?

__________________
* *
-- Paul W. (The Benzadmiral)
('03 Buick Park Avenue, charcoal/cream)
Formerly:
'97 C230, smoke silver/parchment; '86 420SEL, anthracite/light grey; '84 280CE (W123), dark blue/palomino