'91 535 IHKA issues

[botardtim]

Does anyone have information on how to repair or find a new IHKA-II unit for the '91 535. I do not believe any other years will fit, or maybe late '90 to early '92. The problems with the unit cause the A/C, Recirc., or the R. Defroster not to work. I have ruled out that it is the three switches. Any help would be greatly appreciated.

Thanks,
Tim

[shogun]

Have you checked the IHKA control module?
Look for 'cold' solderings. Resolder and check again. Maybe that helps.

[botardtim]

Have you checked the IHKA control module?
Look for 'cold' solderings. Resolder and check again. Maybe that helps.
Yeah, I took the IHKA unit apart, i did find a Thermistor not properly connected, but i did resolder it, but same symptoms. The circuit board it covered with a red sealant type substance that's nearly impossible to pick through.

[Javier]

unloader relay, preventing the A/C, and the rear defoger to work. Just a wild guess. There is a recent post about "No Battery warning light" that may help you identify this relay.

Javier

[Scott C]

Does anyone have information on how to repair or find a new IHKA-II unit for the '91 535. I do not believe any other years will fit, or maybe late '90 to early '92. The problems with the unit cause the A/C, Recirc., or the R. Defroster not to work. I have ruled out that it is the three switches. Any help would be greatly appreciated.

Thanks,
Tim

Tim,
I had a similar problem with my IHK (95 though) in that the AC and rear defogger would work at idle but as soon as I got some RPM's they would kick off. I bought a used one using junkyard dog from Wash state for 130$ with a 1 year warranty. The "new" unit fixed me right up (and I had given up on ever fixing the AC as I could not justify spending big bucks for someone to look at that system). In my case, I think the power regulation failed but no easy way to check due to all of the coating on the board.

Scott