512TR AC - intermittent power

I need some help. The AC push buttons on my 1994 512TR work intermittently. When they don't work, no evaporator fans, no AC, when they do, cold air blows out of the vents. By accident, I was looking for a blown fuse and I bumped the "I" connector on the driver's side of the fusebox and everything started working. I removed the "I" and "J" connectors, cleaned the contacts and replaced the connectors and all worked well for several months, but now it's back to intermittent and random and the fix above does not work. I want to trace the wiring path to and from the push buttons.

I have tried and tried to follow the wiring diagrams in the workshop manuals, but I can't figure them out (they are repos of marginal quality). Can someone tell me which wire on which connector brings power to and from the push button switch and from there which wire exits the fusebox to the evaporator fan? I would be much obliged, and can then start hunting the problem.

 

Ah, now we are getting somewhere. Which relay handles these controls?

 

Tim: Great advice, I now have a plan. Is there an separate electrical manual for the 512TR? If so, this is invaluable, and I need one, as 90% of the repairs I have made over the last 15 years are electrical in nature. I have the Dave Helms Fuse Box upgrade, and I intend to do the gold terminal conversion one of these years.

I have circuit testers and digital voltmeters and a basic knowledge of electrickery, but despite hours poring over the wiring diagrams in the shop manual with a magnifying glass, I cannot decipher the circuits.

Do you have the time to provide a detailed circuit path from the ignition switch to the condensor unit? I need simple, like "power goes from the ignition switch via a blue wire to pin 2 on the H connector and provides power in to the AC relay 5. The push button grounds relay 5 via position 2 on connector H via fuse 5, etc".

You say there is a relay in the AC control unit on the console? Mel indicates a control unit behind the fuse box, but I don't recall that many separate units behind the fuse box as indicated in the picture. I also do not recognize the two larger control unit he pictures. Mel, can you explain further?

Also, Mel, thanks for all your past help. Wolfie has the package from the panel-beater and returns here in 12 days.

And yes, photos will be provided.

 

Mel, I don't recall ever seeing those Bosch relais on the 512TR, and the picture of the area behind the fuse box does not look right either, but my memory may be playing tricks on me.

 

I agree.

 

That will get done later today. I changed all the relays out for new Bosch units 5 years ago, but you never know.

 

OK, I know the problem. Now I need to know how to fix it quickly, as I plan to take this car on my annual golf vacation to Sandestin, Florida in 10 days (about 1100 miles total).

On the "I" connector at the fusebox (6 contact vertical connector on driver's side), with the key in "run" position, the second contact from the top (yellow/black stripe) and the bottom, or 6th contact (solid yellow) wires are hot. Power from these contacts activates both relay "G" (air conditioning system control and relay "S" (key controlled services). The push buttons on the console either ground or allow voltage to the AC unit, working the evaporator fans, etc.
Both contacts must have power for the system to function. The push button also controls power to the AC compressor clutch.

My relays are both good. When I wiggle the "I" connector I can hear/feel the relays making contact, and, if i physically push in on the "I" connector, everything works. Just to make sure, I made jumper wires with spade connectors and inserted them into the "I" connector contacts 2 and 6 and then touched the other ends to the corresponding terminals on the circuit board, and voila! - everything functions perfectly.

Now that we know the problem is in the "I" connector, how do I correct it? Is there a way to crimp the terminals so that they make tighter contact? Do I have to take the terminals out of the connector, and, if so, how? I plan on installing the Dave Helms Gold Connector kit in the future, but I need a fast and dirty fix for right now. I already tried cleaning the contacts with electronic cleaner and applying Stabilant, which seemed to help for a while. As a last resort I can fashion 6 individual jumper wires, but there must be an easier way. How to I take the connectors apart?

 

Yes, please. I am a quick learner.

 

Is there a trick to opening up the connector to get to the contacts?

 

The "I" connector in question is opposite the blue "K" relay. I've removed and re-inserted this connector many times trying to search a malfunction in the starter circuit (top white wire). The connectors are only rated for a specific number of re-insertions, then they start to fail. I've just spoken with Tim (tf308) and I'm going to obtain some new connectors from Mouser Electronics in the AM, meanwhile I will take the connector apart and try to squeeze (tighten) the connectors and see if it works.
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I took the wires out of the connector, none look broken or burned. The male connectors on the board appear intact and solid. Can I simply crush the female connectors a tiny bit with a pliers to increase contact pressure until I can obtain and install new connectors?