UPDATE: Problem resolved! Short version.... Issues was a bad HVAC AC/Heater Control module. Replaced it with one from a 2002 SLK230 from the salvage yard. Why not the OEM part? Well, it was cheap and I was curious to see if it would fit/work! Read the below thread for more info. Thanks to the folks who replied!

Hello all.

Long time Crossfire fan, first time owner. I searched all over but have not found an answer to my problem anywhere.

I'm working out the electrical bugs as I have some battery drains. 1 was the alarm siren, I unplugged it. 2 is the REST function staying on with the key out until the battery is completely dead.
The aux pump and blower motor (low) stays on and the heater control valves are hot without running the car at all. The REST button does not turn it on/off, the REST light on the button does not come on.
I live in Florida so I really don't need the REST function and would just disable it if I knew how.

Fuse #15 seems to stop the pump and the heater control valve but how do I stop the blower from continuously running? I ordered a new resistor but I'm not sure that is going to fix it.
Looking into Mercedes with the same feature I found this relay "N11/6 Automatic heater control time-limit relay" . Does anyone know if/where this might be in the Crossfire or how the REST function knows when to shut off? thanks

 

Only .01 amp draw with fuse 15 and 36 pulled + siren Unplugged. The blower resistor should arrive tomorrow, I'll post an update after I install it. Everything else worked fine, REST just would not shut off.

 

Thanks for that info. Please continue to update. We all learn by experience.

 

Update:

I'm still determined to track this down or at least have some kind of work around to disable the REST function that is stuck on. I did find that if I pull fuse 37 and put it back in, REST turns off but as soon as I run the car and shut it off it turns back on. 😑

I installed the new blower motor resistor but there was no change. Same REST battery drain and a new issue popped up from pulling fuse 15. My heat stayed on because the duo value default position is open. To got around this, I opened up the duo valve and moved the springs that keep the valves open by default from the bottom to the top so it pushes the valve down/closed position instead of up/open. Keep in mind I'm leaving fuse 15 out, no power to the valve at all. (credit random Mercedes forum for the idea). Yes, it disables the heater but I need AC most of the year here in FL.

My remaining drain kills the battery in about a day. When the car is off I still have 1.8v going to the blower motor resistor plug middle pin\wire. I think it's going to come down to the AC Heater control being bad but there still have to be something that provides that 1.8v to run the blower and know when it should shut off after 30min or the battery drains.

Anyway, I'll keep at it.!!!

Other stuff I've done...

- disabled the TPMS (Tire Pressure Monitoring System) warning light
- Installed LED bulbs in overhead light, trunk, marker lights, fog lights, running lights in headlight corners, glove box and tag lights.
- painted trim around the windshield, wheels and calipers matte black ( I use Dupli-color Engine paint enamel with ceramic, awesome paint very forgiving and easy to fix if you screw up.)
- Chrysler logo on my center caps were dark brown/yellow from weather. I could hardly see the logo. I discovered that if you heat it up for a short time with a lighter (maybe 3 or 4 seconds) you can peel the outer clear rubber off and the aluminum logo underneath looks like new again.
- stopped the hatch noise with electrical tape.
- unplugged the alarm siren
- replaced the power seat relay
- replaced the battery
- cleaned the leaves out from under the cowl, replaced the seals around the wipers to fill the gap
- replaced the cabin air filter
- removed the spring from the ashtray so it stays in.

 

If the Rest light is not on it is not the Rest coming on just the blower is staying on. Did you install a Behr resistor or a generic brand? If you installed a generic one then most likely it is defective. You are better off installing one like this https://www.autohausaz.com/pn/2108206210

It is possible it is the HVAC module/climate control but usually it is the regulator.

 

There are three pins on that socket that goes to the blower resistor, #1 and #3 provide a constant 12+volts, the black or brown wire provides the earth.
The centre pin socket #2 and the earth socket provide a variable voltage to control the fans speed. If you are getting 12+volts constant from both sockets and earth it is the AC/Heat control on the dash causing the problem.
I purchased a cheap regulator/resistor and it was DOA. I replaced it with a Behr.
I imagine that the power is switched off automatically only when the circuits are working as they should otherwise they are just bypassed. There must be some sensor that measures the battery power but I do not know where it is.

 

I did buy cheap, generic. The REST light never comes on. The button does nothing to turn REST on or off and I could not get the diagnostic function to work, holding the button down etc.. The recirculate works with the car running and that does turn on but no REST light ever.

 

Careful. You have 1.8volts on there, but if you yank that wire off the resistor, is the 1.8v coming from the resistor (if so, it's bad) or from the wires coming from the controller? (If so, it's the controller. This is a very simple thing to isolate - it's the resistor or the controller - you must verify which and you will know what you have.)

 

Did you ever have a draw on fuse 35? Does the back plate for the odometer, clock, and temperature stay on with the key removed? Our 2004 Limited has those symptoms but we have not yet isolated the one amp draw. Fuse 35 feeds the instrument cluster and I believe, the heater controls so I wonder if our issue is similar to yours We installed a battery cut off on the negative terminal to prevent the battery from draining but this is inconvenient for my wife when she wants to take the car to work and of course the clock, radio stations and possibly other memory features are lost whenever the battery is disconnected. The back light issue seems to be an obvious cause but could just be a symptom of a problem elsewhere in the system like the heater controls. I will be following this thread with interest. I intend to get another instrument cluster to test weather the back lights stay on but the one I want is 90 miles away and removal does not seem to be simple and easy so we just haven’t gotten to it yet.

 

The 1.8 volts was from the wire, it read 0 on the middle pin with the 12v hot and ground only connected to the resister. I did confirm the issue is the AC/Heater control. I'll post more details when I'm done but I found a control module off a 2002 SLK230 for $10 at the salvage yard. Looked way different from the back but the plug is the same. I hooked it up and all problems resolved!

So now I'm trying to see if I can change the temp wheels otherwise I'll have to shave a bit off the wheel area to fit it in the same trim piece.
Everything else is exactly the same size. the buttons are black and the dials are black, surround section is white.. The snowflake/ac button is actually opposite on this one.The EC button light on turns OFF the compressor (outside air only)and red light off means AC is on. Compressor must be controlled by the dials or something.

 

I gave up on swapping the wheels on the sides and installed it as is, looks great!

I trimmed a little from the insides of where the wheels go into the trim piece with a Dremel and a flat file. I took off a little at a time from the back of the trim, keeping the angle AWAY from the silver on the front. I probably could have taken more time and took off a hair more but it fits! The left side sticks just a little bit. right side moves completely smooth. I am just so glad everything works. REST turns on and off, everything else works just fine and it looks like a factory fit.

It seems like a better quality part, It only has one circuit board, not 2 that plug into each other like on the Crossfire. If you take the Crossfire ac/heater control back section off, one of the circuit boards comes off with it. Seems like a poor design IMO.

I doubt I'm the first one to try this, it's good know there are alternative to the factory Crossfire controls. I'm sure the SLK controls are more likely to be available at the salvage yards.

 

@CaptainHero when I was checking for drains I only found a drain from the alarm siren and from REST staying on non stop. 35 might have an effect but there are 5 fuses related to the REST/climate control .When REST wouldn't shut off the blower, aux pump and duo valve stayed on draining the battery.after using the junkyard SLK control module I hooked put all the fuses back and put the springs back in the proper location in the valve. Everything works now, (except the siren I unplugged) no drain. I'll put my charger on the battery overnight and double check the draw tomorrow.

 

Update: I checked the actual battery drain after letting it sit all day. I have 0 voltage drop and it shows a draw of 0.01 AMPS or 10 milliamps or less if I let it sit a little while. I'd say that is pretty good considering when I started this quest to fix the issue the battery would die within 2 to 3 hours.

@CaptainHero I pulled fuse 35 to test/compare for you but it did not make any difference. My clock, temperature etc.. stays on for about 30 seconds after the car is off then it all shuts off. When that stuff is on for that 30 seconds my draw is 0.1 AMPS then after it shuts off it drops to .01 AMPS.

 

Sounds quite normal, to me...


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Typo I corrected, drops to .01 amps or less but yeah, that sounds normal!