IHKR 1 re-soldering ... paging Shogun

[shogun]

Nice instructions, pingu
thanks a lot.
Actually I am also not that 'qualified' in soldering electronics, last thing I 'repaired to unrepairable condition with the soldering iron' was something in our household and my dearest asked me to stay with my car repairs ;-)

[RockJock]

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.

By cool air I mean un-heated air (same as ambient external temperature). I can’t feel any difference in degree of temperature when I adjust the dials.

I’ll check/follow-up on your suggestions/advice when I have some time and I’ll keep you posted …thanks.

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.

The first image below shows the region you’re referring to (red circle on the lower right). The power resistor appears to have leaked/oozed some material that has hardened (‘browned’ where coincident with subjected heat). There are also other areas (integrated circuits) that show similar features (circles with red ellipses). Is this normal? (i.e., thermal transfer paste/compound/adhesive) I’ve never seen anything like this on any motherboards, NICs, video cards, sound cards ..etc that I’ve seen.

Thanks for the soldering write-up/advice …..

[pingu]

That brownish gunk is nothing to worry about - as far as I can tell, it's just glue/filler. The stuff at each each of the integrated circuit (IC) labelled "3.7007" is to hold the IC securely in its socket (aerospace electronics sometimes uses twine to prevent ICs from popping out of sockets).

ICs don't tend to run warm (and your IHKR is from an era long before roasting hot Pentiums) so the fact that the gunk is brown doesn't seem to imply that the gunk has been getting excessively warm.

The disc shaped component to the right of the aluminium channel looks like a transient suppressor (as opposed to a resistor) for absorbing voltage spikes. That gunk isn't from the suppressor. Instead, the transient suppressor would have been coated in that gunk at the time that the IHKR
was manufactured - probably to stop the suppressor from getting knocked about (it looks like it stands proud of many of the components, and may have needed some extra support). Again the transient suppressor shouldn't really ever get warm unless your electrics are shot.

Although you're right that gunk is unusual on motherboads and other lower voltage electronics, it's quite common in power supplies - power supplies tend to have tall skinny capacitors that are susceptible to getting knocked over - hence the gunk.

I'm amazed by the complexity of the IHKR - it is really just for running climate control? It's probably got more computing power than the Apollo spacecraft.

[shogun]

It is also for the rear window heater control, but that is also not so complicated.
And maybe also for the rear view mirror heater control (? not sure about that, would have to check the wiring diagrams)

[RockJock]

i finally got around to looking at this problem again and managed to fix the issue:

1) re-flowing the solders on the two resistors in the IHKR did not solve the problem.

2) heater valves closed properly when applying power.

3) heater valves weren't getting the correct voltage.

4) the micro-switch on the left hand climate control dial (i.e., drivers side) looked a little cooked/browned.

======> $45.00 climate control unit off E-Bay solved the issue, now i just need to get my A/C re-charged with R12 to start troubleshooting the A/C.

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. yay!!