AC wiring diagram

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bavbob

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Anyone have a AC wiring diagram for insight into my 72 E3?

Whenever I put the heater blower motor on OR the AC, fuse #9 (only says heater blower on the fuse box) heats up. Also happens even if I disconnect the power to the compressor or to the heater blower motor. AC compressor clutch also does not engage.
 
Here's another diagram:

Wiring%201.jpg


Wiring%202.jpg


Based on your description, I would check the relay that shuts off the heater fan. It is item number 5 in my diagram and in my 72 it is mounted just below the fuse box using a bracket that is held in place with the same screws as those used to hold the fuse block.
 
So if the relay fails testing, does anyone have a source for the old Hellas or do you rewire the connector to a newer 4 prong type and get an updated Hella or Bosch relay ?
 
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I'm not giving up on this. There are 2 relays associated with the AC and heat, I pulled the one near the box and the resistance measured Zero and when joined to a 12V source, clicks. When the heater blowers is on, fuse 9 heats up somewhat, when the AC is put on, the heater blower shuts off as it should but the fuse heats up very fast.

The second relay is near the coil, I pulled it, it clicks ok, resistance measured 17.9 ohms, not sure if that is where it should be . Regardless, when pulled ( ie, knocking out the compressor and aux fan), the above will still happen.

I can only conclude that the relay near the fuse box is bad despite it testing ok on the bench????
 
I think your problem may be with the relay near the coil. The relay near the fuses is intended to allow the blower to operate unless the a/c fan is turned on. Thus, it should not show resistance in a resting state. This is what you measured (assuming you measured terminal 30 to terminal 87).

The other relay is supposed to be off unless the a/c fan is turned on. If you are measuring 17.9 ohms of resistance from terminal 30 to terminal 87 on this relay (without the a/c fan on), there will be a current flow where there should not be one.

Measure this again, checking that you are measuring terminal 30 to terminal 87, without a current from terminals 85 to 86.
 
Seems to me that heating (of anything electrical) suggest that it's carrying more current (amps) than it was made to. Sooooo..... if something's heating up (in this case a relay) I would verify the amps going through the connections, particulary on the "downstream" side of the relay, now that you have two candidates for the AC wiring.

I'm led to wonder if there isn't a ground somewhere there shouldn't be, or a component is partly shorted to ground internally.

Time to get out the multimeter, set to the higher amps range, and read some current flows. If the fuse is 8 amps (f'rinstance), I'd set the meter to the 10 amp range and go looking, though I'd be happier about that if the meter had a setting higher than 10 amps so I might not blow a fuse in the meter. Them are not as cheap as the ones we put in our car's fuseboxes.
 
Yes, checked the relay on the bench, out of the car, I will double check to ensure I was at 30 and 87.

Since these are NLA, has anyone ever used the shell of an original relay, filled it with a new one for the sake of originality?
 
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