W124 A/C Wouldn't restart until car was restarted.

[JamesDean]

Evening folks,

Oy what a terrible commute home. First off, I get on 77 and make my way to the turnpike only to be greeted by a massive line of cars..all the way back to 77.

So in the midst of this waiting my engine temp climbed up to 100C, which it normally does with a/c but I figured I'd turn off the a/c since I've only got one good pusher fan right now. The other one spins well but just doesn't power up.

40 minutes later I make it to the toll plaza to learn that there was an accident on the west bound side of the turnpike and the tollbooth workers were telling people to turn around. FYI I go east.

On the other side I pop the a/c back on..and get nothing. Meh whatever, windows down, roof open.

Then it starts to rain. Windows up, roof open. (on purpose, it didnt break LOL)

It turns out that at 75mph, the rain wasn't heavy enough to fall into the car so it got carried away by the wind. Kinda cool.

I get home, turn the car off, hook up my gauges to check pressures. I figure either a) the compressor failed b) it all leaked out.

Well it was c) nothing. Static pressure was about 90 psi. Turned the car back on gauged moved around and I got cold air.

So I think I have a pissy sensor somewhere but I'm not sure which.

I know that on some days when I turn the key on my pusher fans will come on and stay on for a bit. Not sure if thats related or not.

I've got a set of 140 pusher fans that, one day, I might attempt to retrofit. I got them for like $10 figuring what the hell, even if they dont fit, it was only $10.

So my question to you guys, any ideas on which sensor or maybe a relay?

[Jeremy5848]

I had that problem years ago, think it was either the Klima relay or the PBU (push-button unit of climate control). It has to be de-powered (turn off the car) and then powered up again before it will allow the a/c compressor's electric clutch to engage. Replacement is about the only option.

Sorry to be so negative and poor of memory -- it was a good 5 years ago!

Jeremy

[jay_bob]

I vote Klima relay as well. If the rpm sensor on the compressor and the rpm sensor on the engine don't agree, the Klima locks out and will not reset until power cycled.

You do have a temperature cutout switch on the thermostat housing. However I believe that one self resets if the temperature drops to a safe level again.

I would look for the root cause as the Klima might be doing its job due to a belt problem. On the 603s with serpentine belt it is there to protect the rest of the engine systems from a locked compressor.

[JamesDean]

Hrmmm I might suspect the Klima before the push button unit. I have a sneeky suspicion that something was holding the relay open in there.

I might have to open it up and have a look see this weekend. Unless I've got one laying around here hmmmm...negatory

003 545 69 05

is for diesels only.

[JamesDean]

Originally Posted by jay_bob

I vote Klima relay as well. If the rpm sensor on the compressor and the rpm sensor on the engine don't agree, the Klima locks out and will not reset until power cycled.

You do have a temperature cutout switch on the thermostat housing. However I believe that one self resets if the temperature drops to a safe level again.

I would look for the root cause as the Klima might be doing its job due to a belt problem. On the 603s with serpentine belt it is there to protect the rest of the engine systems from a locked compressor.

Hrmm. In this application its a 602 but I think the principle is the same anyway.

I've got a new belt on..maybe 2k miles on it.

I do know that I hear some groaning from something when the a/c is on... maybe it is causing belt slipping and speed differences? I'm not sure. Never did find out what was causing it.

[jay_bob]

Yes same deal on the 602 as the 603, they are essentially the same up front.

If you are getting noises up there pull off your fan and belt and then grab hold of the things that spin around looking for end play and roughness. Your tensioner might be going out, causing erratic operation of the compressor sensor.

Belt tensioner, lever, shock and spring is north of $200 for the good stuff but the peace of mind is priceless.

[JamesDean]

I was looking through my car records and it looks like the tensioner was replaced already at 201k (currently at 263k)

Also looks like my timing chain, guides and cam gear, motor mounts were all replaced around 197k.

[jay_bob]

Well it sounds like your belt ought to be ok, unless the replacement tensioner hardware was subpar quality.

Got a scope? If so I would monitor the tach signal coming into the Klima and see if it is good. Also check the engine signal. I would dual-trace it and compare.

Looks like the compressor sensor is on pins 9 (+) and 11 (-), engine speed on pin 2 referenced to ground.

If the compressor sensor is bad I believe they can be serviced without replacing the entire compressor or discharging the system.

[JamesDean]

Yeah I've got one of these low cost scopes
DS1052E 50 MHz Digital Oscilloscope | Rigol - Beyond Measure

Should be well up to the task.

I just think it was odd because I was stick in bumper to bumper traffic on the on-ramp, just turned it off. 40 minutes of 100C later, popped it back on after I went through the toll plaza and nothing. I thought maybe the heat + cold solder joint...

But I'll peep the signals and post a capture on here.

[funola]

Originally Posted by JamesDean

Yeah I've got one of these low cost scopes
DS1052E 50 MHz Digital Oscilloscope | Rigol - Beyond Measure

Should be well up to the task.

I just think it was odd because I was stick in bumper to bumper traffic on the on-ramp, just turned it off. 40 minutes of 100C later, popped it back on after I went through the toll plaza and nothing. I thought maybe the heat + cold solder joint...

But I'll peep the signals and post a capture on here.

I maybe in the market for a portable scope. That's a nice one you have. What other scopes have you looked at/ recommend?

[JamesDean]

Originally Posted by funola

I maybe in the market for a portable scope. That's a nice one you have. What other scopes have you looked at/ recommend?

For all my needs and uses that scope has done well and its affordable.

When I bought it there were posts around the internet about it having the same hardware as its bigger brother
DS1102E 100 MHz Digital Oscilloscope | Rigol - Beyond Measure

And all you need to do to access this hardware is to update the scope's firmware and you'd be good to go.

I still haven't done it but I recommended either of these scopes. They affordable and work well.

Here is a review:
http://www.eevblog.com/2009/04/05/full-review-of-the-rigol-ds1052e/

[jcyuhn]

You tripped the rotation sensor circuit in the Klima relay, so it shut down the compressor until restart. Don't over-rotate on this; start with the simple stuff. Two common causes of this scenario are excessive air gap in the compressor clutch and dirt/oil on the friction surfaces. The air gap is specified as 0.50mm. In my experience compressor engagement becomes unreliable once it increases to 0.75mm or so. If the gap is too large you can reshim it to adjust downward. A good automotive a/c shop will sell a kit of shims for the Denso compressor.

Degreasing is as simple as using a good spray of simple green, or brake parts cleaner, or whatever works for you in the clutch air gap. Rinse with water and see if it works better. Sometimes this is enough to get solid engagement and not trip the rotation circuit.

[JamesDean]

hrmm interesting. It worked fine this morning on the way up to work. Maybe I'll give it a spray down and clean it up a bit.

[funola]

Originally Posted by JamesDean

For all my needs and uses that scope has done well and its affordable.

When I bought it there were posts around the internet about it having the same hardware as its bigger brother
DS1102E 100 MHz Digital Oscilloscope | Rigol - Beyond Measure

And all you need to do to access this hardware is to update the scope's firmware and you'd be good to go.

I still haven't done it but I recommended either of these scopes. They affordable and work well.

Here is a review:
Full review of the Rigol DS1052E | EEVblog - The Electronics Engineering Video Blog

Thanks for the info. Is it battery operated? Can't find it in the specs which is odd. Also can't find size or weight. Maybe I didn't look hard enuf. Some forum postings about building a battery pack for it suggests it's not. That's a negative.

Are probes included or have to buy separate?

[JamesDean]

No its not battery powered. It got a standard IEC 3 prong cable.

2 Probes were included, standard scope probes.