BMW Repair: BMW 1990 535i-no heat-vin#WBAHD2313LBF63995, coolant level, temperature gauge

Question
Dear Don,
My BMW 1990-535i-vin#WBAHD2313LBF63995 has no heat.I noticed that recently-maybe over the last 2-3 months-when I put the heat on-it seemed to be getting weaker in intensity.Then the other day when I put it on-and drove with it on for some time-there was no heat at all!A funny thing happened though last night when I put the heat on-very briefly-maybe 2-3 minutes-some mild heat did come on-but shortly thereafter-back to no heat whatsoever!I had one garage check it and they said there was heat up to a point(they could feel it)-but, in their words-there seemed to be  a junction-electrical, or a "valve" that probably was not operating correctly.They did not have good experience in working on BMW-so they did not go any further.They would not troubleshoot any electrical or "valve" problems!I briefly spoke to a mechanic at another location who had quite a good reputation-and appeared tobe the in house foreign car expert-and his first impression upon hearing this was that probably the"regulator" was involved,and may be faulty.He was very busy,however,and did not check anything!I then made a call to a third mechanic with an excellent reputation, and specializing in foreign cars-and he was so busy ,he could not immediately look at it-but suggested that sometimes "the computers go haywire."I checked the coolant level, and it is good.I did note ,however,recently also-that the temperature gauge has sporadic bouts in which it does not work at all!Sometimes the needle stays all the way down to the left(cold side)-and does not move.then all of a sudden-it may jump back up to the middle.It never goes past the middle towards the hot side-maybe only slightly.Maybe 5-6months ago ,I replaced the water pump,and the mechanic cleaned some contacts under the hood that amde the temperature gauge run better for a while-as it had been misbehaving for up to a year prior to that!I am most anxious to learn what you think-the car has approximately 180,000 miles on it-and I really love it andwant to keep it.Also,if this matters-if the radio is onand I put the rear window defrost on a lot of static ensues.Some codes I have had for along time are:check control,and ESD Regelt.The air conditioner has not run or be functional for quite some time, as I had it checked, and needs a new compressor.I hope you can help me and can you also speculate-that once you determine what it is-what it might cost to fix-give or take?I deeply appreciate any help you can give.Thank-you.

Sincerely,


Dan  

Answer
My first thought would be to look at the water valve.Its located under the hood near the heater core outlets.There was a problem with the diaphrams leaking and temp wasn't regulated,as it leaked internally.I'm not sure of the cost,you used to be able to replace justr the insert(held on by 4 screws)
As for the check control light check the panel and it will illuminate the circuit that has its fault(a bulb,or low level)