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1997 SLK230
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467 Posts
Discussion Starter · #1 ·
Today my 1997 230 developed a new issue - when I got home and turned the engine off and removed the key the Aircon/Heater Fan kept running. For now I have disconnected the battery and will get SDS on it in the coming days and start to work through the issue. From what I have read these symptoms often point to the Hedgehog resistor/regulator being faulty.

However, I have other symptoms:
  1. Heating has stopped on both sides - suspect the switched ground PWM signal to the Duo valve is AWOL
  2. The EC light on the aircon switch is always off
  3. The recirculation switch also appears to do nothing and light is always off
  4. The Fan speed control does nothing - the fan always runs (including when there is no key in the ignition) but at a mid range speed.
My thought is my modification to retrofit the secondary electric coolant pump (not fitted in early pre-facelift R170s) may have "fried" the HVAC controller. This is because in addition to controlling the Duo valve the unit now also controls 2 relays that mirror the state of the two halves of the duo valve so that the new electric pump only runs when one or both of the duo valves are open for heat. These are low current relays but nonetheless I fear they may have pushed a 24 year old module "over the edge". BTW this mod is fully written up in the DIY section and until now has worked really well.

I will update on progress in due course but would welcome hearing from any members who have suffered anything similar or just want to place bets on a likely cause.
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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From what I have read these symptoms often point to the Hedgehog resistor/regulator being faulty.
Exactly that, don't buy a Chinese Fleabay effort, they are rubbish. Buy Hella or whoever is OEM, I think when I did mine last year it was Hella but I've slept since then :ROFLMAO:

Aircon likely needs ReGas but I expect by now the Condenser Rad has a leak ;)

I always thought the Booster Pump runs full time as soon as the Engine starts, my Car is F/L, it has had 2 good used boosters and then they die after a while so I gave up, the only time it has any effect is when sat in traffic Idling, the Heat Temp drops, but merely resting a toe on the throttle so the idle comes up to around 1000 rpm, (put it in neutral if auto), sorts that out, and tbh I don't drive the Car much in winter, and we don't get stuck in traffic much where I live ;)
 

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1997 SLK230
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Discussion Starter · #3 ·
Exactly that, don't buy a Chinese Fleabay effort, they are rubbish. Buy Hella or whoever is OEM, I think when I did mine last year it was Hella but I've slept since then :ROFLMAO:
@Dave2302 many thanks as always for the feedback and advice. I shall certainly be looking for an OEM replacement for this. The weird thing is that today I put the battery lead back on to drive it into the garage to put on SDS and everything was perfectly normal. However, that hedgehog has definitely had its final yellow card. I fired up SDS and the stored fault I got in HHT was "B1416 Heating water circulation pump A31m1". This cleared OK but if this is referring to the electric pump I have retrofitted how on earth did it know it was there at all! Rather puzzled by this.

Aircon likely needs ReGas but I expect by now the Condenser Rad has a leak ;)
The aircon does lose a bit of gas over time but the Condenser was replaced under warranty just after I bought the car. HHT reported an Evaporator Temp of 5 degrees for an outside temp of 17 degrees with refrigerant pressure varying a bit but around 8bar. What was odd is that yesterday everything went from working to not working in an instant but is all OK today when running in the garage. Will take it for drive in a bit as the Sun has just appeared.

I always thought the Booster Pump runs full time as soon as the Engine starts, my Car is F/L, it has had 2 good used boosters and then they die after a while so I gave up, the only time it has any effect is when sat in traffic Idling,
The reason I fitted the pump was a total lack of meaningful heat when stuck in traffic in the winter. I tried everything to fix this but the only successful answer was the pump. I must admit to having overthought my wiring solution whilst not properly looking at how it worked as a factory fitted system. I now believe you are absolutely right that the pump should run whenever the engine is running. I assumed that the fact the pump was connected to the HVAC control was that it was controlled like in a central heating system and was only asked to run when there was a demand for heat. I completely missed the other reason the pump is fitted to the car which is for the residual heating function. I now believe this is probably the only reason for the connection to the HVAC controls. On the later HVAC controls when you press the Recirc/Rest button its sorts the flaps and runs the electric pump to provide heat from an already hot coolant system.

I have now removed the relays and quickly rigged the pump to run whenever the ignition is on and all seems OK. I have no real confirmation of what happened yesterday so will monitor carefully over the coming weeks and see what happens.

I am very minded to get a later version HVAC controller and wire up as per the factory fit and also get a new hedgehog installed.
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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FWIW my Hedgehog failed and flattened my Battery overnight, then it was OK for a while, then same thing, only this time I heard it running before it flattened the Battery so I replaced it, no issues since ;)

I think your HVAC knows the Pump is faulty for one of two reasons, either the Control Panel has already been replaced with a newer on which is looking for a Pump, or it sees the Temperature difference when Idling, not sure if it has / or how the R170 temp Sensors work never had a need to delve .............

Mine had that same Pump fault, I swapped in a good one, Code went away for almost 12 months then the Pump failed again and the Code came back, I haven't bothered changing it again, as I said above it doesn't inconvenience me, one day I may fit another one ;)

HTH ;)
 

*Registered
1997 SLK230
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Discussion Starter · #5 ·
Thsnks Dave. Ok I think I'll just get on with changing that hedgehog asap. My pump is actually a new Bosch one so pretty sure that's ok. My HVAC control is the original 1997 one that has no REST function or connection for the pump. I think I am definitely going to change these controls as thinking back on several occasions I have had that smell of something electric being hot (if you know what I mean?) and possibly the odd crackling sound although that could have been my knees...

If I do go for an updated version I will need to run a wire from the pump to the controls. I guess a route through the bulkhead is not too much of a problem but getting the extra connection onto the plug maybe. My initial enquiry to MB resulted in a "these contacts are not available separately from the whole harness" response. Looks like I will need to find a fully wired plug and splice onto my harness. More fun...

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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What I would do is get the Harness Plug with a short length of wire from a scrapper, then carefully cut away the plastic so you are left with one or 2 terminals with wire tails that will fit into your cars wiring plug ;)
Less splicing that way ;)

Curious that your HVAC Controller is reporting the Pump as faulty as it never knew about the pumps being as it is an early one :ROFLMAO:
 

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1997 SLK230
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Discussion Starter · #7 ·
Thanks for the excellent suggestion - I shall definitely do that.
It is very puzzling how SDS can report on a pump it shouldn't know is exists. These Germans are very clever so maybe they have incorporated an ESP module somewhere. If only it could display next weeks winning lottery numbers.

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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It's the HVAC Module that is telling SDS there is a Pump Fault ....................

Perchance did you version code HVAC to tell it you fitted the Pump ?

BTW, ESP Module is fitted, it's part of the ABS Module on the Pump, but nah, it won't give us Lottery numbers, I tried that but couldn't find the Lottery listed in SDS functions list :ROFLMAO:
 
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*Registered
1997 SLK230
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Discussion Starter · #9 ·
I now have a later version of HVAC controls including plug and harness tail on it's way to me.

I can see why people are tempted by the Chineseum hedgehogs. I have just been quoted just under 拢250 by 2 MB parts department. I have found Febi ones on offer for 拢50(ish) which feels much more appropriate. But I may wait a day or two until I have done a most mortem on the current HVAC control panel for evidence of cooking injuries.

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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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Febi is likely fine as is Hella if available, got mine from Euro Car Parts, just don't buy Chinese Amazon / Fleabay tat ;)

Assuming I just found the right Invoice it was Hella p/n 5HL351321011 that I fitted to mine :)
 
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*Registered
1997 SLK230
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Discussion Starter · #11 ·
Cheers for the info - replacement Hella unit now sourced.

It's the HVAC Module that is telling SDS there is a Pump Fault ....................

Perchance did you version code HVAC to tell it you fitted the Pump ?
Sorry I forgot to respond to this question. No I didn't version code the HVAC to tell it about the pump. But I suspect I will need to do some version coding when I fit the replacement HVAC controls that support the pump as it's from a 1999 C Class 220Cdi. Any pointers on what I will need to do?

As always thanks for your help and guidance.
 

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2004 SLK230
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I gave up trying to repair my heater blower, its got a mind of its own, Off on the dial seems to be on, setting one on the dial seems to be off, its does this all the time, air con works ok just the heater plays up.
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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I'm not entirely certain a C Class one will work ????
 

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1997 SLK230
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467 Posts
Discussion Starter · #14 ·
I'm not entirely certain a C Class one will work ????
Oh dear but guess I will find out the hard way. It's the correct part number A2108303185 (E Class?) As given by EPC. Interestingly only the initial 2 versions of this part were A170 numbers all the subsequent "replaced by" parts are A210 numbers.

On the plus side it was cheap at 拢16 and returnable at postage cost (and some scrappies want that much for a cable harness plug and wiring tail).



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**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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210 is an older E Class one yes, that may well work, do some searching, @M4rCu5 and I discussed these ages ago, I think I have a 210 one in mine or perhaps a 209 clk ? dunno :(

I went for Black Face Dials, so used an HVAC with black faces but I seriously canna remember the p/n's ;)
 

*Premium Member
2001 SLK200K/2001 SLK320
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210 is an older E Class one yes, that may well work, do some searching, @M4rCu5 and I discussed these ages ago, I think I have a 210 one in mine or perhaps a 209 clk ? dunno :(

I went for Black Face Dials, so used an HVAC with black faces but I seriously canna remember the p/n's ;)
Lol, you've got a W208 in yours, I've still got a W210 in mine. :geek:

EDIT:
The early W210 has the internal air temp sensor built-in which makes it bulkier out back and the nylon fingers are a lot looser/floppier - combined, these 2 issues make it a bear to fit. Later W210 or W208 is the way to go (y)
 

**Premium Member '02 R170 SLK V8 5.0 & '00 SLK320
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*Premium Member
2001 SLK200K/2001 SLK320
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Thanks :)

That's the one, I've done mucho sleeping since then ;)
I know the feeling :ROFLMAO:


Oh dear but guess I will find out the hard way. It's the correct part number A2108303185 (E Class?) As given by EPC. Interestingly only the initial 2 versions of this part were A170 numbers all the subsequent "replaced by" parts are A210 numbers.

On the plus side it was cheap at 拢16 and returnable at postage cost (and some scrappies want that much for a cable harness plug and wiring tail).
I've got a A 210 830 29 85 from a W208 CLK ready to drop into the 320 when I get a round tuit, I don't foresee any problem at all with your xxx 31 xx (y)

Pix for comparison..

R170:

Camera accessory Cameras & optics Point-and-shoot camera Film camera Digital camera Gas Audio equipment Office equipment Machine Temperature Gas Tints and shades Machine Composite material Automotive exterior

W208:

Audio equipment Automotive design Auto part Camera accessory Electric blue Automotive tire Gas Audio equipment Auto part Cable Circuit component Auto part Trigger Automotive fog light Fashion accessory


HTH
 

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1997 SLK230
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Discussion Starter · #19 ·
Thanks guys - my replacement has just arrived and it looks like I have the early 210 that's going to be a PITA to fit :(

Audio equipment Camera lens Gadget Point-and-shoot camera Office equipment


Never mind I like a challenge... providing it's not totally impossible!

BTW There is definitely something kaput in my original unit as this morning I put the car on SDS again (to see what might need coding) and as soon as DAS scanned the TAC module during a quick scan the light on the Recirc button flashes, the fan stops and nothing else works. Interestingly the quick scan shows no faults under TAC. But once the scan moves onto the next module the HVAC is all back to normal. If I then do another quick scan the TAC module is totally AWOL! It didn't behave like that last time so it's got to go. Fiddling around I did eventually get HHT to connect to TAC (whilst the Recirc light was flashing) and under Actuations I can change the fan speed all OK even though it was totally dead from the front panel at this time. All very weird. Frustratingly I am not going to get to put the new controls in until sometime next week. I'll report back in due course.
 

*Premium Member
2001 SLK200K/2001 SLK320
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Thanks guys - my replacement has just arrived and it looks like I have the early 210 that's going to be a PITA to fit :(

View attachment 605509

Never mind I like a challenge... providing it's not totally impossible!

BTW There is definitely something kaput in my original unit as this morning I put the car on SDS again (to see what might need coding) and as soon as DAS scanned the TAC module during a quick scan the light on the Recirc button flashes, the fan stops and nothing else works. Interestingly the quick scan shows no faults under TAC. But once the scan moves onto the next module the HVAC is all back to normal. If I then do another quick scan the TAC module is totally AWOL! It didn't behave like that last time so it's got to go. Fiddling around I did eventually get HHT to connect to TAC (whilst the Recirc light was flashing) and under Actuations I can change the fan speed all OK even though it was totally dead from the front panel at this time. All very weird. Frustratingly I am not going to get to put the new controls in until sometime next week. I'll report back in due course.
That's the one that I've got in the 320 atm and it was a bear to fit, prepare to lose some skin off of your hands and knuckles. The air turns blue as well :censored:

On mine at least, the fingers flop about a lot more than on the "slimmer" editions which makes the job rather challenging to start with :( After much faffery and finally getting the fingers "home" I then discovered that I couldn't get the wiring plug in so I had to take the module out and start over, fitting the plug first :mad: :censored: I then discovered that there are wires/cables, radio leads, aerial lead etc. that want to push that boxy bit out whilst I'm struggling to get the fingers home again .. frustrating much but they do go .. eventually (y)


Vehicle Motor vehicle Steering part Steering wheel Automotive design
 
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