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K Jetronic issue

Started by beagle2022, 17 July 2011, 06:39 AM

koan

#15
You're right again MT, twice in a row, must be a record ;)

I agree with your description, not at first but after a few minutes with a volt meter and vacuum gauge you are correct.

Thought that the 100C switch only turned on the aux fan and nothing more.

My investigations on my AU car today show:

The firewall mounted A/C changeover valve controls manifold vacuum to distributor retard diaphragm.

With A/C off the valve is deactivated (no volts) and passes manifold vacuum to distributor diaphragm holding ignition "retarded". This is the normal ignition timing set point.

With A/C on and compressor engaged valve is activated and line to distributor diaphragm is vented to atmosphere and distributor moves to advanced.

If 100C switch closes aux fan turns on but also activates valve and distributor advances irrespective of
A/C compressor state.

If 85C refrigerant temperature switch operates the aux fan turns on but does not actuate the valve (valve will operate anyway if A/C compressor clutch pulls in).

When engine warms up, 65C switch in manifold passes throttle plate vacuum to distributor advance diaphragm but only when throttle is moved off the stop. Advance diaphragm easily over comes retard diaphragm and "wins" off idle)

This is not like the AU wiring diagram I have. It shows the distributor retard connected only to the A/C clutch and 100C and 65C switches connected only to the aux fan.

Always trusted the wiring diagram before, I'll have another look but pretty sure it doesn't allow for the above behaviour, now wondering what else is not quite right with it.

Thanks MT for the new knowledge.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

Did you read that TJ ?

That fundamental disagreement you can shove right up your ass  8)

TJ 450

I think it will take about ten years for my ego to recover, MT. 8)

Tim
1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500

beagle2022

It seemed like such a simple question and now people are in therapy!

I have clearly opened a major sectarian debate.  I will replace the dead sensor anyway and see what happens.  I'll let you know the outcome.
Sydney, Australia

Big_Richard

one thing you can be certain of, is that even though these cars finished rolling off the production line 31 years ago, we are all still constantly learning about them  8)

koan

Quote from: beagle2022 on 20 July 2011, 06:45 AM
It seemed like such a simple question and now people are in therapy!

I have clearly opened a major sectarian debate.  I will replace the dead sensor anyway and see what happens.  I'll let you know the outcome.

What it means is that here you can be sure of getting accurate information from people who are passionate about their cars, who actually work on them, and don't propagate baseless myths (unlike some other forums).

A few people in therapy is a small price to pay for that!

I have to go now, I have an appointment...

koan
Boogity, Boogity, Boogity, Amen!