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  #1  
Old 06-06-2004, 01:52 AM
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Question for 190E owners who've had max heat/heater valve problem

Hi all.

I've got a '93 190E with the popular max-heat, default condition with hot blowing out the sides and dash. I've read every post I can find on the subject for 201s and 124s, but I can't find any single post which lists the sequential things to check, so I'm asking for assistance from someone who's had this before.

The condition appeared a couple weeks ago. I thought the cheapest, easiest fix was the heater control valve under the cowl by the wiper. I changed it today, but it had no effect. Playing with the extracted one, it still opened and closed normally when I applied 10-20 psi orally (no flames please, my benz is a girl). So I don't think that was the problem. 12 years and the thing still worked fine. It was a 16 dollar dart so I thought I'd try it.

I don't think the vacuum delivery to the top of the valve is functioning. The line seems to hold pressure, but I don't think there's any vacuum actuation created. I tested the new valve with the vacuum line disconnected from the top, and the lever freely moves open-closed, open-closed. When I attach the vacuum line, the movement of the lever is restricted, which leads me to believe the line is pressurized, but not sucking when it needs to.

Another thing that's weird, I let the car run today and manually held the heater valve closed, for like 3-4 minutes, and the side vents still blasted hot air. I would have expected them not to, with the valve closed. Maybe this isn't a valid test?

The a/c system on this car has been shot for about 3 years, with a coolant leak somewhere, but I don't know where. I'm fine with no a/c when the alternative is a couple/few dimes to fix. Chicago is hotter than hell but usually only for 2 months, then it's back to cold. Hopefully, correcting the max heat can remain independent of the faulty a/c.

Can one of you climate control or vacuum experts give me some ideas for the next couple things to check?

Thanks in advance for any assistance.
Mike. Just turned 156K...badge time.

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  #2  
Old 06-07-2004, 10:57 AM
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Monday morning bump in case any 190 owners checked in.
Any assistance is greatly appreciated.
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  #3  
Old 06-07-2004, 05:52 PM
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mikeohart:

Since no one elsa has chimed in I will give you my personal experience. Note, I am not an expert and some of the diagnosis I had done with a professional. Furthermore, my car is an 88´190e with AC.

Now you are having problems with you system is similar to what I was having some time ago. First off, are you sure that you changed the correct heater valve? On my car the heater valve actuator is more like @$100.00 part (if I recall correctly).

Now these heating/cooling systems are worked with actuators that are vacuum controlled. On my car, there are 3 behind the dash and then the heater control valve somewhere behind or in front of the firewall. On my car I was having problems directing the air flow and the air mixture. The diagnosis was that one or two of the actuators behind the dash were bad. To get to these you need to take out the dash on these cars. To check them, there is a central vacuum control unit behind the dash to the right of the glove box. To get to this, if I recall, you need to take out the glove box and from there you can connect your mighty vac to check vacuum on the different actuators.

Also, on my car, the Klima relay was bad which was also causing problems. Not too sure of your car has a klima relay but on mine it is located behind the batery next to the OVP fuse.

lastly, another source for the problem on your car can be the push button control that is in the dash. I have heard that you can pull these out and resolder the joints and it should give you a little more life out of them. Same thing with the Klima relay.

Hope that this helps you somewhat. If you do a search on ac - klima relay - actuators you may get more information.

Iggy
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Insanity: doing the same thing over and over again and expecting different results.

2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
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Old 06-07-2004, 05:54 PM
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Oh forgot to mention, in my personal experience a freon leak was the easist and cheapest part of the system to repair!!!!
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Insanity: doing the same thing over and over again and expecting different results.

2006 - Suzuki Gran Vitara (2.0 L fully equipped) Like this car so far except for trying to put on the seatbelt.
1988 - 190e - 2.3L - 172K miles (It now belongs to the exwife)
1999 - Chevy Blazer LS Fully Equiped - killed it June 2006
2001 - Honda Civic EX - 68K miles (sold June 2004)
1963 - 220S - Dual Carb 6 cyl. (sold)
1994 - Yamaha WaveRaider (fun to ride)
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  #5  
Old 06-07-2004, 06:31 PM
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Without vacuum, the default is to send heat to the cabin. When my car was blowing heat full-time, the problem was a cracked vacuum line. Next to the fuse box you should see 1 or 2 yellow check valves. These check valves direct vacuum to the climate control system and if you have it, the economy gauge in the instrument cluster. Check the lines leading to and away from these check valves.
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  #6  
Old 06-08-2004, 11:06 AM
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Mike,

Glen is right, you probably have a vacuum leak some where. The vacuum switching valves are located approximately under the right front speaker. You need to remove the glove box to insure you have vacuum at that point and all the connections are good. Try to examine the visible vacuum lines/connections before you take out the glove box as those would be the easy solution.

Tinker
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  #7  
Old 06-08-2004, 01:34 PM
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Thanks for the advice guys. I'm going in.
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  #8  
Old 06-12-2004, 12:05 PM
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Update

Low and behold two of the vacuum connectors (boomerang shaped) were slit at the seat of one of the yellow valves. For the bottom one in the picture...both were slit on this yellow valve.

Replaced these connectors with hose pieces (freebie from dealer) but the problem still remains.

Attacking on both fronts, as I have the glove box off in anticipation of changing that valve in there, also working on stereo while I'm at it.

Question though, why the discoloration in the bottommost valve nipple? The others aren't like that. Looks more like burning than dirt.

Trying to figure the sequence of the breakdown of my system...did the slit connectors cause a breakdown of other parts in the system (e.g. valve in glove box?)

So if I've still got hot air out the sides, and have changed the heater control valve and corrected connector leaks, the valve in the glove box is the next logical thing to try?

...these yellow deals are thermo-vacuum valves? Is that right?
Is that burning indicative of failure and I should replace it?

Thanks in advance for your past and future assistance.
mike
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Last edited by mikeohart; 06-12-2004 at 12:13 PM.
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  #9  
Old 06-12-2004, 05:39 PM
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Ifi you don't have a strong vacuum source, there will not be enough vacuum to pull the heater valve closed.

What is your economy guage doing? Is it in the left half of the range?

The switching valves do fail, but you need to make sure the vacuum source is strong and then work forwards. There are all sorts of connectors in the vacuum system. Some are only accessable with the dash removed. If one of them is leaking, you probably won't have enough vacuum to force the heater valve closed.

Tinker
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  #10  
Old 06-19-2004, 12:47 PM
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Solved

For those who might pull this when doing a search, the problem was an additional vacuum leak that I had missed. The 4th connection, just out of the picture range, had a sliced connector. If you put your ear up to it, the leak was obvious.

Steve at Pinnacle (Woodridge IL) helped me out. He and Brian are great guys and I highly recommend them.

The 190 lesson learned is to check ALL vacuum connections before tearing things up looking for valve or actuator problems.

Thanks to all those who chimed in.

mike

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