Engine Bay Pictionary

[garydan]

What am I looking at here? I'm trying to start diagnosing my AC. I just purchased this truck and from what I can tell the wiring is all fuggered up. I see no electrical connection to the compressor first of all. And I have these other connectors and what I think may be a vacuum hose connection hanging loose.

Can you help identify what I'm seeing in these pictures? It's a 1985 K5 Blazer with a 400ci motor.

Picture 1

Picture 2

Picture 3

Picture 4

You can see all my pictures here: http://k5.javagator.com

Thanks!

 

[Kenny78]

Pic 1 I dont know what that goes to but I do not think it has to do with A/c

Pic 3 is a temp. actuated vac. switch. I dont know if it controlled EGR or what, but you dont have that emission component anymore.

All the other pictures are of the ESC system that modified spark in the original 305 motor.

A/c compressor feed/switch IIRC is green. Pics of the compressor/firewall and climate control box would be more helpful.

 

[lak2004]

If its an 88 it would have come stock with TBI fuel injection so you probably have some stuff in there that is not needed for a carb'd engine. I would be interested in knowing what that part is in the 4th pic as well though.

 

[Blue85]

Pic 1 is the power for the ESC module (under the dash). I think it piggy-backs onto the distributor power connector.

The 1x4 WeatherPack connector in Pic 2 goes to the ESC module. It would have plugged into a harness coming out of your distributor, but somebody either bypassed it or swapped out the distributor for a non-ESC type.

Pic 4 is the "tip-in" vacuum switch for the ESC system. It's supposed to briefly reduce spark advance when you first get on the throttle.

Obviously your ESC has been disabled. The 400 probably does not have a knock sensor in it anyway.

Picture 3 is a thermally activated vacuum switch. I don't think your intake manifold came from the '85, so it's anybody's guess how the vacuum lines are set-up on that engine. You would have to follow them to see. Here is a stock '85 (49-state) label:

 

[Blue85]

It looks like you have the pancake style compressor (pictures of the A/C components would help here). Looking at the clutch from the front, the connector is between the compressor and the clutch at the 9:00 position.

The A/C wiring is very simple. The dash switch supplies hot when one of the A/C modes is selected. This goes through the low-pressure switch (located on the receiver/dryer) and then powers the clutch. The other side of the clutch (it has a 2-pin connector) just gets wired to the block/manifold. All of these wires are green.

You can jumper the clutch on for just a second with a wire to verify that it engages. Measure the resistance of the low-pressure cycling switch. If it's more than an Ohm or two the clutch can't engage. Either the switch is bad or you are low on refrigerant (or it's really cold outside). If you get some moderate resistance value (10's or hundreds of Ohms) then the switch is bad. The switch can be replaced easily, but it's cheaper and works just as well to use the old switch to engage a relay.

 

[garydan]

So far it seems like all the pictures are ok. I guess I don't have an "ESC" system. By the way what does that stand for anyway? (EDIT: Electronic Spark Control... I figured it out) I know its not Electronic Stability Control Well thanks to the tips above I found the connector for the AC compressor:

I know where the big connector hooks up to, I found it at the 9:00 position that Blue85 mentioned. Could someone let me know where to hook up the other two connections (one looks like a ground connection and the other connector is smaller)?

I guess I can just hook up the ground somewhere on the block or intake manifold, but what is that other connector for?

 

[Blue85]

Ok, the ring terminal can go on almost any bolt on the engine or brackets. The connector that your lower green arrow points to goes on a little sensor sticking out of the side of the block. You would find it just below the header primaries, between #1 and #3 IIRC, if it was the stock 350. I can't speak for your transplanted 400.

 

[garydan]

Ok, the ring terminal can go on almost any bolt on the engine or brackets. The connector that your lower green arrow points to goes on a little sensor sticking out of the side of the block. You would find it just below the header primaries, between #1 and #3 IIRC, if it was the stock 350. I can't speak for your transplanted 400.

Well this is what I have: That connector from what I understand is for the water temp.

 

[garydan]

Still trying to figure out about the smaller connector. I attached the electrical connections today to see if they were working. No luck, I hooked up an electrical tester to the two pronged connector and moved the AC switch, and nothing happened. I attached the connector to the compressor, and the compressor didn't seem to engage. So I'm wondering if that other connector needs to be attached to something.

 

[Blue85]

Well that's where that small connector went. The new engine may have a different terminal on that sensor, which is why they ran a new wire. Or they may just not have known what to do. If the temp gauge works, you might want to leave well enough alone and just button up what is already run.

The little connector does not effect the A/C.

What tools do you have? A/C pressure gauge? Voltmeter or Ohmmeter? Test light?

If the refrigerant is low, even perfect wiring won't make that compressor engage. To test, take the connector off the low-side switch and jumper one terminal to the other with a wire. If the compressor engages, this verifies all of the wiring. If it doesn't, something still isn't right. Don't let it run for more a second or two if you don't know that state of the system.

My guess is that the system was never charged. The engine swap means that the system was opened up. Why would you vacuum and charge the system and then never hook up the wiring?