Re: [MBZ] cycling hot/cold in 90's w124 300TDt
Ok,this morning as temps drop to freezing the drive into town with the teenager became interesting since on the left side of the wagon it vented fresh outside freezing air, on the right side, hotish air. Turning the dial on left to almost max made it a bit warmer, click to high and you get heat, lots of, way too much to live with, otherwise my left foot gets frostbite. This has to be resolved. Fortunately the dealer had two temp sensors for me, so it's either those, or the potentiometers, or the control unit is screwed, since I believe the dual mono valve is fine. Later this evening I tackled the job of confirming the two blower housing sensors are ok. First of course I found out the fan dial refused to come off, I know I had it off before to replace the little bubs in the back lighting and in the control unit!. Pull tug, plead, invent new words (old words actually), snaps in two. Sigh... Small vice grips to pull off the inner plastic housing which is as you know pressure fit on, the outer dial is melted onto it with now broken stubs. Off to a great start since we've busted plastic, and this was the easy part. So unscrew upper console wood, remove nuts, bulbs, place wood somewhere safe far away from the work area, prod at switch matrix. The interesting thing here is the dual manual climate control is two temp dials, a seperate fan speed controller, and vacuum controller for air vents. Not much there on the control unit proper, but a large nest of wires and a small 30ish pin conector with a locking tab, wires head off mostly to drivers side. Has to be a control unit somewhere else there just isn't anything in the switch assembly. Well there could be perhaps the manual system is really simple and the circuit board is the size of a pack of cards? Well since I'm here I carefully examine temp dial, unscrew right housing, temp dial and housing comes off. See nice large, clean heavy duty looking potentiometer. Well that looks reasonable certainly wasn't full of dust we'll not touch that further. Carefully examine connector, check tab yes it releases, try to separate. Nope, begs to snap plastic parts. Fiddle, prod, poke, examine, stand on my head to see underneath. Nope try some pressure and 30ish pins welded together creak and the connector releases and the two parts separate. So I move the switch matrix aside and dangle on driver side. What's left is a fan speed switch and a vacuum actuator controller pod screaming touch me and I'll leak air. Peering about I can see yes on the left according to the w124 USA manual there should be the temp sensor right behind the control unit which snaps into the blower housing. Yes it's there. Ok look to the right, where I suspect the right temp sensor should be. Goodness knows what the overhead temp sensor does on this car. Yes a rectangular hole where the right side temp sensor should be. No temp sensor, just a hole into the right blower housing, no wires, nothing. Mmm certainly there has to be a temp sensor. I'll bet the evil telco that messed with the installation and deinstallation of the cell phone popped it off and it's lying in the bottom of the console. Look about, nope but odds and ends of non benz wire lurks. Nothing leaps up and says here am I, that would be too easy. Ok remove radio. I need to do this to replace it anyway, attempt to insert radio keys, right one goes in, left one only part way. Fiddle lots more, then jam left one in. Radio won't budge. Pull, face plate pops off, well it does that anyway, still no go. Assume I am an idiot and can't read instructions and swap keys, nope. Sigh, ok I really wanted to avoid all this extra work, remove center console storage box, unscrew center console wood, pull back, leaver out ashtray, or attempt to. Sigh, ensure brake is on, turn power on, step on brake, put shifter in neutral, finally wiggle out ashtray assembly, disconnect power cord. Jam two small screw drivers into stupid lock tabs. Pull radio out, disconnect the 8 pin becker cable, the 4 pin cable, the ground, and a mystery yellow handcrafted wire which I think later is the Phone Mute feed wire. MMm still no temp sensor, It's an inch long, termocouple on end, size of your thumb, two pins has to be there somewhere. Lots' of wire, wires for phone coax, cable to 2nd part of becker box, stereo wires, etc etc. Feed wires to the missing cell controller, few other things. Poke prod. Finally think surely those engineers ran the 2 temp sensors in same wire bundle, follow wire bundle back, then foward and what do you know dusty temp sensor with broken tab leaps out of the rats nest of wire in the bottom depths of the console. So deinstaller did it, I doubt the installer did this since at freezing temps the climate system is quite insane and I doubt the original owner would have survived the years with an insane
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
Now you know why phones and cars don't mix. And especially why 90's and later MBZ and the monkeys who work for phone/stereo stores don't mix.
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
First running the dial on the right side 5-7C colder (seems) to regulate things a bit. So I wired up some benz pins/sockets, after doing the relays for my 500E headlights I've a few wires and pins about. Check for connectivity, then cross connected the two solenoids. The hot air then switches to the driver's side from the passenger side. This seems to indicate the $300+ duo-valve assembly is working and the signal it is receiving is bad. So either the control unit is bad, or one of the temp sensors in the left/right heater box is bad. The temp sensors are $20 each, could I ordered a pair and we'll look into replacing them. It still could be the potentiometers on the dials or the control unit, I guess I could disassemble the console and test them, then find they are bad, reassemble, disassemble (sigh). Er no it's a bitch to reassemble the console and align and retighten everything based on my last experience, plus all the plastic whimpers break me, so we'll just order them. On 6-Nov-05, at 5:40 PM, John M McIntosh wrote: So it appears that right side is heating up, so it could be dual- valve is weak on one side, or is the control unit flaky? Mmmm I wonder if I can swap the female connectors or reverse the connector. That would tell me if the control unit signal is flake if the swap alters the behaviour from side to side. Well the connector is specifically designed to disable anyone from casually or even forcefully connecting backward. The little plastic tabs scream, touch me and I'll snap off so I won't rewire it. Tomorrow I'll visit radio shack and gets some alligator clips and wire and cross connect things and see what happens. That and run the temp dial 5-7 C colder on the right and see if anything changes. John 1983 300TDt 358k Kilometers (mobil 1 Delvac) 1990 300TDt 149k Kilometers (mobil 1 Delvac) 1993 500SEL 168k Kilometers (mobil 1 0w40)
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
Ocsillating temp is usually caused by a bad temp sensor blower, so that the cabin air isn't being pulled past the sensor -- car has to be pretty warm before the sensor heats up, then gets pretty cold before it cools off. I'm not familiar with the dual control system, but I'd bet you have two temp sensors, and the suction blower (located under the right hand outer dash vent on the single control systems) is bad, or the hose has fallen off. Peter
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
John M McIntosh wrote: Now that cold weather as set in I've been chasing a gremlin in the climate control. First this 90's wagon has manual fan speed/vent control with dual temp controls. It slowly cycles between blowing mid temp, to hot, then to cold when you've set things to say 20c I replaced the interior temp sensor, but testing of the old one seems to show it's ok anyway and the behaviour did not change. At the duo-valve assembly, I cleaned the contacts and I know that if it's disconnected that I get heat even if dials are set to min cold. Plugging in the circuits gives me hot at max, and cold at min. Ohms across the valves gives zero. So I assume the valves mostly close otherwise I would not get cold air on both sides. My cheap digital multi-meter won't show voltage cycling, but I get 12.75 on heat, and 13.5ish on cold on both sides of the plug (3 prong, assuming center plug is ground). So does this imply the push button unit is bad? Thoughts are welcome. The manual climate control system is unlike ANYTHING that's documented in the US manuals. From you description, It's not like my Euro 201 either. See if you can find someone on the Continent (like Richard Becker) that has the diagnostics of that system. That's your best bet. I agree with Peter, it could be the aspiration blower. Will the blower pull enough air thru the vent to suck smoke in or hold a piece of tissue against the vent where the cabin sensor lives? When it fails the temperature control usually becomes erratic and uncorrelated to what you select. Marshall -- Marshall Booth Ph.D. Ass't Prof. (ret.) Univ of Pittsburgh School of Medicine [EMAIL PROTECTED]
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
On 6-Nov-05, at 4:24 PM, Marshall Booth wrote: The manual climate control system is unlike ANYTHING that's documented in the US manuals. From you description, It's not like my Euro 201 either. See if you can find someone on the Continent (like Richard Becker) that has the diagnostics of that system. That's your best bet. I agree with Peter, it could be the aspiration blower. Will the blower pull enough air thru the vent to suck smoke in or hold a piece of tissue against the vent where the cabin sensor lives? When it fails the temperature control usually becomes erratic and uncorrelated to what you select. Marshall Well I can sit in the car for a few minutes (15 or so) and run it, goodness that will trash my mpg stats. However a) I've stuck the 1 cm square paper up on the vent and it stays there, stays there for many minutes, never falls. b) Confirmed that new temp sensor seems to give a ohm reading which matches expectations, versus zero or infinity c) I've 5V at the connector so some electronic widget is supply control voltage. Leaving the paper up there causes heat (lots of) when set to 20C Take paper away and think as everything goes to cool. Ah, temp on right side center vent goes up slowly, temp on left side seems constant. Then temp on left side goes down, followed slowly by right side, car gets cold, then repeat cycle. Ah, that would explain the wave of heat (direction undetermined) then the side vent freezes my left hand on the steering wheel. So it appears that right side is heating up, so it could be dual- valve is weak on one side, or is the control unit flaky? Mmmm I wonder if I can swap the female connectors or reverse the connector. That would tell me if the control unit signal is flake if the swap alters the behaviour from side to side. Peter questioned if I have two sensors, I only see one up there, the hose comes across from the passenger side pillar then attaches to the elbow joint of the temp sensor. So does it just decide that temp up on the left side of the panel would be a mixture of both sides? -- === John M. McIntosh [EMAIL PROTECTED] 1-800-477-2659 Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com ===
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
So it appears that right side is heating up, so it could be dual- valve is weak on one side, or is the control unit flaky? Mmmm I wonder if I can swap the female connectors or reverse the connector. That would tell me if the control unit signal is flake if the swap alters the behaviour from side to side. Well the connector is specifically designed to disable anyone from casually or even forcefully connecting backward. The little plastic tabs scream, touch me and I'll snap off so I won't rewire it. Tomorrow I'll visit radio shack and gets some alligator clips and wire and cross connect things and see what happens. That and run the temp dial 5-7 C colder on the right and see if anything changes. -- === John M. McIntosh [EMAIL PROTECTED] 1-800-477-2659 Corporate Smalltalk Consulting Ltd. http://www.smalltalkconsulting.com ===
Re: [MBZ] cycling hot/cold in 90's w124 300TDt
Yes, in reading on the UK benz boards there appears to be 2 heater core temp sensors, and one interior sensor in the head lamp. Tomorrow with some wire I'll swap feeds to the duo-valve assembly and see if the heating issue follows. If it swaps sides then either the temp sensor on the right side heater core is bad or the control unit. If it does not swap sides then the valve managing the right side heater core water feed is bad. On 6-Nov-05, at 10:14 PM, Peter Frederick wrote: John: Temp should change at the same speed on both sides. Sounds like you have a bad water control valve, causing excess heating on one side, so the other is too cold. As I said, I'm not familiar with that system, but there HAS to be some sort of temp sensor for each side. It may be in the heater box instead of the overhead, though, to set the correct temp in the ductwork. Peter ___ For new parts see official list sponsor: http://www.buymbparts.com/ For used parts email [EMAIL PROTECTED] To Unsubscribe or change delivery options go to: http://striplin.net/mailman/listinfo/mercedes_striplin.net
