I have these main 2 here (HVAC and FANS), and some of the other pages it references, but I haven't yet been able to find any additional info where the different splices are, such as S117, S190 etc. Not yet, I'm still looking lol

 

I was asking about the handful of splices in the engine bay since I'm roping off a complete system. All the main runs from the PCM to the relays, pressure switch, compressor, and evaporator temp sensor aren't difficult. Finding out where some of these splice points live, or making them is what I was looking for. I can walk the harnesses down by hand if I need to.

I'll be testing one of the evap temp sensors today, and that solid state box it has. I believe that almost any probe type thermistor would work in case a probe fails, but that solid state box is integral to the system.

 

I've printed the applicable schematics, and using highlighters, and wiring lists 😄. I'm an avionics engineer by trade so I'll get it eventually as long as I have all the resources.

 

EXAMPLE:

The fan schematic is page 8A-31-2 (assuming you have 3 relays) as you have posted above.

On that schematic are splices S113, S117, S119, S122, S190.

Turn one page to 8A-31-3

At the bottom of that page are the splices called out above. Note that the splices are further differentiated as being for the (L32) V6 or the (LT1) V8

Look at the line for each splice.

The second column is the LOCATION. If the location of the splice can be shown in words, that is all you get.

If the splice location is further detailed, the third column tells you what page to look at in the 8A-201 section.

The fourth column tells you which figure on that page shows the splice. Sometimes they are not quite correct. For example, to find splice S190 turn to page 201-36. There is no figure 68. But flip pages until you find figure 68 (on page 8A-201-39). Splice S190 appear to be in the harness bundle coming out of the Underhood Electrical Center.

It may be helpful to study Shoebox's engine harness photograph to follow the written descriptions.

1995 Z28 A4 Engine Harness

 

Haha, it was on the very next page!

Thank you, this will help locating splices, or creating them if they don't currently exist. Yes, I'm going with the late model, 3 fan relay setup, and terminating it to the PCM + fan motors etc - accordingly. Hopefully no issue with the tune, although I doubt it, since the vehicle's build date is May 28, 1994. A late build - so the PCM should be tuned for dual fan control even though it came from the factory with a single large fan and I'm converting to the 2 fan set up. I'm going to order all my wire, crimp tools (2), and terminals from EFI connection. I've gotta get the terminals for the fuse block (Underhood Electrical Center?) and that weather pack crimp tool. All my components and hoses/brackets, o-ring kit have arrived, except for the compressor. I'll be ordering that shortly and a compressor harness pigtail with the 1amp diode already installed (I'll check the bias with a DMM).

Taking measurements and will order the wire soon. It'll be better to rope it off first while I've got all the components out of the way, terminate, perform continuity and power pin checks, then install components and go from there.

It's late, I'm debating on testing those slightly damaged evaporator temperature sensors with a DMM and some water.

 

As a retired electronics test engineer, I recommend that, of course. According to historical documents, the German V2 extensive testing by their engineers resulted eventually in the success of the US space race. Who knows where things will lead.

 

I don't have a power supply, or injection meter for the 5VDC reference voltage, but I should be able to still read resistance changes between contacts A and C right? Wasn't sure if I should measure there, or A to B, then C to B. Was going to measure between A and C, check resistance, then place the probe in ice water and see if the resistance value changes. Then of course do the same with a little warm water.

I've been in the private space race now almost 10 years. They all said we couldn't recover a booster from space and relaunch it, they were wrong 😄

 

I got around to testing the evaporator temperature sensors. Both sensors read approx 17 kohms at 72° (black lead to C, red lead to A) , and went up and down several thousand kohms whether in ice water, or warm water. Resistance increased with cold, decreased with heat. Ranco is the manufacturer with PN 52458970 and E45-1000-000 on the small black box.

Looks like I should have a working sensor for this install.

 

Looks like it. But...your testing is way wrong. This is a powered device and needs 12vdc to work properly. The apparent "resistance" at room temperature is 400 Ohms, not 17k Ohms. You have realized that the "resistance" changes over temperature, so in one regard it is active to some extent. You can't test a powered sensor with a resistance measurement. I realize you do not have a dc power supply....but you do have a 12v dc power source...the car battery. Long wires to the sensor would suffice. Anyway, your sensor may work only because it exhibits signs of life.

 

I was thinking it was more like a thermocouple (dissimilar metals) and realized it's more like an RTD.

It looks like the PCM steps down the 12 VDC to 5 VDC for the solid state device. At least that's what it looks like via the schematic. A DC power supply set to 5 VDC, (current?), then perform the same tests would be ideal. Could also measure the voltage and current out of that reference contact of the PCM to confirm - then mimic it with a power supply.

Seems the resistance changed by several thousand Kilo Ohms just from changing the temperature and measuring across the sensor. We'll find out one way or the other if they work. Both sensors read the same without power.

 

You are right and I am wrong..old ageism at work again ;-) You need 5vdc like the PCM ref. You can get that from an ordinary wall charger like the one for your phone. Get a charging cable ($3), cut it open and use the black and red wires.

 

I'll wanna check the Amp output from the PCM. I'm not sure if the contact position B29 from the PCM has a >2.5A output. I wouldn't wanna fry the solid state device if it's not rated for 2.5+A. I was out today and didn't think to go pick up and injection meter or small v a small variable DC power supply. I need one for some other projects anyway. I would suspect the reference voltage/current from the PCM is less than 0.5a, and could be milliamps.

I'm also not sure if that 5VDC is there with ignition on, or other configurations have to be met first, I'll check voltage and current on B29 tomorrow with ignition on and see if it's outputting, which it ties into the SFI there as well at S117 so I'm hopeful for 5VDC and a measurable current output.

 

I responded but it's not showing the post for some reason. Need to measure contact position B29 of the PCM for current output. If the solid state device is not rated for >1-2a then I'd be afraid I'll fry it. I'm betting it operates on less than 1a, and perhaps milliamps.

 

The voltage at B29 is fixed. The current is variable, based on the resistance of the solid state box. The circuit in the box should limit current flow. I also need to point out - when you were attempting to measure the resistance of the temperature probe, connecting to pins “A” and “C”, you were actually measuring the resistance of the parallel circuit made up of the AND the probe. To measure the resistance of the probe to find a replacement, you would have to cut the wires.

 

With the solid state device reading 400 some odd kilo-ohms (A -> B, and C - > B respectively), my digital multimeter measured the path of least resistance between points A&C which was approximately 17 kilo-ohms at room temperature. By putting the thermistor in ice water and then warm water the temp fluxated by approx 3,000 ohms both directions. If no current is outputting from the PCM contact B29, I'll need a flat 5 VDC reference with no current output for a proper test. I'll measure it, B29, tomorrow just to check and make sure.