IHKR 1 re-soldering ... paging Shogun

Quick summary (89’ 535iM):

- blowing hot air on both sides no matter what the settings
- replace heater valve assembly still blowing hot
- thus culprit most likely the IHKR 1 (pictured in first image).

- an area on the PC board looks like it’s been subjected to high temps (the second image); two resistors (120R 5%) in this region look rather cooked (quite brown) as well as the back of the board.

- Question: should i try to re-solder these two resistors? BTW – solders look good under hand lens magnification. Checked with a local stealership and the replacement unit is $1,200.00 (Canadian Pesos)…… freakin’ ouch!

Thanks a million in advance!! Cheers!!

http://i79.photobucket.com/albums/j1.../IHKR_1_1_.jpg
http://i79.photobucket.com/albums/j1...N/IHKR_1_2.jpg

if the solders have very very small cracks, simply touching the soldering iron to them should be enough to fix them.

Edit: i am horrible when it comes to electrickery, but couldnt you test the resistors to see if their values are to spec?

Do not buy a new unit from the delaer, that is waste of money. In any case you can get a complete used unit much cheaper. I unfortunately only have IHKA modules at my stock. Maybe someone has some for IHR.

Here is on German 7-forum a pin identification of all plugs, for IHR also as well as the other units. You have to register first on 7-forum to have access. Free of charge, so no problem.
Download it and translate the pin descriptions and try to translate it from online dictionary. If probs, ask here, there are some members which understand Germann
http://www.7-forum.com/forum/showthread.html?t=54790

That looks like burnt and I would replace these items and resolder all black looking items (haircracks/bad solderings).
Maybe a electric/electronic expert can chime in and comment, better than my amateurish approach in electronics.

Read on my website the instructions how to solder electronics.

Thanks guys ...

Quote:

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Originally Posted by Alexlind123

Edit: i am horrible when it comes to electrickery, but couldnt you test the resistors to see if their values are to spec?

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yup, they're within spec .... perhaps i'll just dowse the board with contact cleaner and 'touch' the solders on these resistors ....

@Shogun - if the above procedure doesn't do the trick then i'll follow-up on your info .......thanks!

P.S. .... and there's no way i'll buy from a stealership! :( ....

there's always E-bay: http://cgi.ebay.com/ebaymotors/BMW-E...spagenameZWD1V

does the full hot/full cold have any influence on the teperature?

The 2 big green parts with the slight brown coloration are the are the pre-resistors for the heater valves. Above that are the IC's for the heater valves, each one IC for eachone valve.
They are controlled by the single chip with the sticker on it.
I once had an old processor which did not give a signal to the valve-IC, the right one was working. Then I installed another one.
The coloration of the resistors is nothing special, they get pretty hot and then change the color like a animal/insect which changes color based on background.

but refreshing the soldering at the leads won't do any damage.

Remember valves need power to shut off, so: Is the switch in the drivers side dial closing properly at the settings other than top left click? Is fuse OK? Is the A/C filled with gas? My car also blows hot both sides when the A/C is out of gas. Have you already checked the valves are opened. Is A/C compressor clutch engaging? Is expansion valve OK?

Javier

Quote:

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Originally Posted by Paul in NZ

does the full hot/full cold have any influence on the teperature?

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hot air emanating from vents no matter what the setting. even far left (counter clockwise) 'click' on driver's side. only way to get cool air is to bypass heater core.

Quote:

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Originally Posted by Javier

but refreshing the soldering at the leads won't do any damage.

Remember valves need power to shut off, so: Is the switch in the drivers side dial closing properly at the settings other than top left click? Is fuse OK? Is the A/C filled with gas? My car also blows hot both sides when the A/C is out of gas. Have you already checked the valves are opened. Is A/C compressor clutch engaging? Is expansion valve OK?

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1) fuses ok
2) valves open

i have to check the R12, compressor clutch and expansion valve .. any quick tips (like a how-to)? i'll can search post histories.

thanks guys.

But heater system is OK.

hot air emanating from vents no matter what the setting. even far left (counter clockwise) 'click' on driver's side. only way to get cool air is to bypass heater core.


By cool you mean not cold? If so, the problem is not having A/C working OK.

Can you feel a difference in the hot air by adjusting the dial to the far left/far right? If so, control system should be regulating properly the hot air supply. You can fully close the valves by connecting their Yellow/Brown and Yellow/Violet wires to ground. This will bypass the IHKR control and force closed the valves as long as they are OK, and the fuse is OK and feeding their Green/Yellow wire with battery voltage.

i have to check the R12, compressor clutch and expansion valve .. any quick tips (like a how-to)? i'll can search post histories.

If you set the dial to far right, clutch compressor clutch should engage immediately with A/C on, if not, you are probably out of R12. If clutch engages, you should hear the hissing around the glove box, when expansion valve passes R12. Also should feel the temperature difference between A/C tubes going to the Evaporator, at the engine compartment right-rear area.

Javier

Reflowing the solder joints of the 120R resistors might help and is well worth a go (I've fixed an old TV in this way). I'd also be tempted to reflow the joints of the L475D integrated circuits which are above the 120R resistors, and also the joints of the 4 small resistors on the top surface of the board (the ones that are just below the 120R resistors). It looks like everything in this area has been subjected to many thermal hot/cold cycles and it's this thermal cycling that can cause solder joints to crack and go intermittent.

If you do reflow the 4 small resistors then watch out for the one identified as R233 as it looks as if there's a small wire attached to the right hand side of R233.

From the zoomed out photo, it also looks as if there's another region of the board with a power resistor that's been cooked. The region I mean is about two fifths of the way from left to right along the imaginary horizontal line that streches from where the blue/yellow connectors meet on the left to where the green/white connectors meet on the right. If this isn't just a trick of the light then worth reflowing things in this region too.

At the risk of teaching you to suck eggs, a lot of soldering manuals suggest that you should heat the joint first, then add solder. I've probably soldered many thousands of joints and I reckon that the usual advice can be improved. Intead, put the soldering iron against the joint you want to make or re-flow, then add a tiny amount of solder - the tiny amount of solder will improve the thermal conduction between the tip of the iron and the old joint. After a second or two, add some more solder to the joint (that by now will have melted nicely, thanks to the heat transfer from the tiny bit of solder you added earlier). After adding the main solder, hold the iron at the joint for another second or so (so that the new solder and, more importantly, it's anti-oxidant flux) can do its job, then remove the tip. Should take about 4 seconds per joint from start to finish if the iron is hot enough - you certainly don't want to take any longer than 10 seconds.

If you reflow the L475D integrated circuits then allow some time between each joint for things to cool down - you'v got 16 joints in a small area, and you don't want to cook the L475Ds.

If you reflow the 4 small resistors that are just below the 120R resistors then just give them a tiny amount of additional solder - more will not improve their joints as they look as if they're surface mount (i.e. they don't have leads that go to the underneath of the board) - too much solder will make the joints brittle.

Good luck!