kept stumbling past the "tech section" i guess, i have a couple questions that i am having trouble finding answers to elsewhere, perhaps if i post here.
'79 240D 123 616

1) rear window defroster. Only one line was heating, and only half of it. I looked, and since one side is all connected along, and same with the left side, that even if i fixed that one horizontal line, all the others still won't work. I noticed on the one, in the dark, i could see a spark occuring right in the middle (it's a hot spot, where it defrosts in a larger area than the lines) then on the other side it doesn't work. I have one of those repair kits, but since it's not a few spots, this looks hopeless. Idea's?

2) the front defroster, actually the center switch goes to "high" then to "def" for added air, i think it must shut off the dash or feet for "def". I noticed naer the accelorator, the line is there, with the curled ends and all. when i twist the switch, it actuates, i just don't know where the connection needs to be made. help?

3) any leads on purchasing R12 cans? I have a shop that can refill my system, probably cost $150, when i was told by previous owner (he has a receipt of full car inspectIon) it says "low". I haven't tested it yet, the switch is behind the bezel. the full bezel (where rear defrost switch is too) has been replaced with a "rocker switch only" bezel, no circle for dial. so i need to pull that out and just test the A/C to see if it will even cycle. my experience is they won't cycle if there is a low charge. I thought about getting a 135 retrofit kit, however i've been told that is not good on the system, it was made for R12 and it is harder on it. ideas?

i sure appreciate it

Guy

Don't have much help on the first two, but can help you with number three. R12 is controlled. To purchase it you need an EPA 609 certification. There are a number of websites where you can go and take an open book online test for about $15 to get the certification. You might try IMACA.ORG.

You can then buy it at NAPA or you can usually buy it online for about $15 a can.

You are correct that a low charge will interrupt the system. There is a low pressure switch in series with the clutch to protect the compressor against a low refrigerant situation. Low refrigerant will prevent lubricant circulation.

You are ABSOLUTELY correct in staying with R12. 134 will not cool as well, and statistically will shorten the life of the system. MANY people will promote an alternative refrigerant, but with R12 getting as cheap as it is, it's just not worth it. All the alternatives are either flammables or blends and there are disadvantages to both categories.

Hope this helps.

thanks Larry, this does help that concern of mine. i appreciate news on the certification, that may very well be the ticket.

u can buy the liquid conductor paint, they suppose connect 2 broken circuit together u touch up where the sparks occur , i bought a bottle from wal mart few yrs ago, but never tried it. if it didnt work u have only wasted 10 bucks. is hell lot cheaper than a new glass.
or connect a 12v elec computer fan on the rear shelf, its going to do the same. if u're old enuf these were standard features in the big 3 cars during the late 60s to 70s.
we can even buy a plastic filled with these heated wire and glue her to the rear window during my hey days.

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good thinkin' SD. I just may hook up a fan. I will give it a try, like you say, i'm only out $10. bummer it can only be used once, cures in 30 minutes so not much time to test and test. i will mix half and try that, then the other half if i need to try more.