1985 300td tach fixed on the way to working ac

[johninva]

1985 300td tach fixed on the way to working ac ( hopefully ) It was the egr computer. The formerly leaking windshield may have been to blame. The connector on the the egr computer was terribly corroded. swapped with junk yard egr computer and the tach came to life. jumped the low pressure switch and the compressor engaged, so hopefully I just need a charge.

lucky find at the junk yard this week, a 1985 sedan, scored tach, tach sensor cable and pickup, egr computer, ovp relay, and klima. The 123's that show up in the wrecking yards where im at in central VA have lines formed at them the morning they are brought to the other side of the fence, and are picked clean to the bone very quickly.

Eternal thanks to the forum, without which repairs would be so much more work, if not impossible for me.

so how about a question ?

is there any way to tell if the ac system has been converted to 134, there was an ac company sticker under the hood but the first time i cleaned/degreased under there all the print/writing went away on it, dont recall ever looking at it closely enough to see what it said

I'm not an AC expert, but I believe you can tell by the connection type (assuming it was converted correctly and someone didn't put in some strange "alternate" refrigerant). If it needs a charge, I would take it to an AC shop and let them determine the type, check for leaks, and refill the system.

[fareed]

Hi johninva, is that 1985 a 123 or 124, I am having a problem with the tach on my 84 123 the instrument shop say the cluster tests ok on the bench but will not do anything in the car???
Fareed

[johninva]

w123, but i dont think the 84's and 85's work the tach in the same way. youve got a tach amp, and a differnent pick up style. i dont know about yours cause i aint got one like that. search for cigarette butt fix for tach, i think that applies to your vehicle

[DeliveryValve]

Actually he has a similar set as your '85.

As for his problem, best to check out these diagrams. Start there, follow the test values and do a search on more testing the fellow m-shop members have done. The wiring diagram for the '85 is not exact to your '84