Wiring questions?? '77 280Z to '90 TPI & T-5

[sstallings]

Guys,

I don't want to waste anyone's time, so I've reviewed all the threads I could find, read the JTR Z and TPI manuals a dozen times, and bought and studied the Helm GM, and Diamond Pubs Nissan factory manuals.

 

I've removed all of the headlight, wiper, AC, PS, and other extra wires from my EFI harness, and isolated a few of the Datsun wires that I'll need to keep for guages. But wiring has never been one of my strengths, so determining which of the remaining wires from the bulkhead and 15-pin connectors on the EFI harness match which wires on the Datsun harness has been holding me up for a few days now. I'm not frustrated yet, but I am confused. I have to admit that the GM wiring seems much more straight forward than the Datsun wiring.

 

Has anyone successfully tackled this same conversion (or close to it) that I can correspond with as I try to sort out these last dozen or so connections (primarily fuel pump, ignition, fuse panel, VATs, 2-spd electric cooling fan, etc.)?

 

Also, it seems that I should replace the existing fuel pump relay with a double-pole relay to control both the low pressure pump to the surge tank, as well as the high pressure EFI pump. If that is correct, does anyone have a wiring diagram for that circuit?

 

I've read a couple of threads that recommend wiring the two-speed Ford Taurus fan for a manual switch. Has anyone wired it for a thermostatic switch as well as an AC switch? I plan to use a Vintage Air AC system with a switch to bump the fan to high when the AC is on, as well as a thermostatic switch. Is that the right way to go, and if so, does anyone have the wiring information for the electric fan controlled by two separate switches?

 

I think I'm getting close, but I still need some help.

Thanks,

Steve

[sstallings]

Okay,

So now I'm answering my own questions, but that's okay -- I think they call that "learning." I found a good book on automotive relays and answered one of my questions. I can wire both fuel pumps through the existing fuel pump relay as long as the combined amperage draw of both pumps does not exceed the rating of the relay. I should also leave a margin of safety in case of a surge at start-up (not usre how much so I'm thinking about 20% should do it). If the total is too much, I can run a new relay in parallel using the same source circuit to trigger it to support the additional low pressure pump to the inline surge tank.

 

I still haven't figured out the Ford Taurus two-speed cooling fan circuit, but hopefully I can get Ford wiring information without having to buy another Helm book (or whoever prints Ford manuals).

 

I've got the tach and ignition wires sorted, and I'm working my way through the rest of the 280Z to GM TPI connections. When I'm finished, I'll publish the whole set so the next guy will have a better starting point. Although I'm still waiting to hear from someone who's done this before me, if only to verify my connections.

 

Keep the shiny side up.

Thanks,

Steve

[DavyZ]

Steve, good job on persevering and learning everything by yourself...and then sucking it up and posting about your experience rather than getting bitter about it. You're a man.

 

As far as the Taurus fan is concerned, there should be a substantial amount of information within the site to cover this topic. True, the wiring of the two speeds seems to have a number of members stuck, but I recall more than one person having the solution to the problem and having completed it successfully. I hate to tell you to search, but I do believe the nugget of knowledge is out there for you.

 

 

Davy

[deja]

Like DavyZ said congrats on sorting it out on your own. You'll be better off in the long run if you do that so in the future if you have porblems you'll know how you did it. Make schematics of everything you do.

One note about your idea of running relays in parallel. That works in theroy but in the real world one relay will always close before the other one and that will defeat your plan. Get a higher current relay if you need it.

 

Okay,

So now I'm answering my own questions, but that's okay -- I think they call that "learning." I found a good book on automotive relays and answered one of my questions. I can wire both fuel pumps through the existing fuel pump relay as long as the combined amperage draw of both pumps does not exceed the rating of the relay. I should also leave a margin of safety in case of a surge at start-up (not usre how much so I'm thinking about 20% should do it). If the total is too much, I can run a new relay in parallel using the same source circuit to trigger it to support the additional low pressure pump to the inline surge tank.

 

I still haven't figured out the Ford Taurus two-speed cooling fan circuit, but hopefully I can get Ford wiring information without having to buy another Helm book (or whoever prints Ford manuals).

 

I've got the tach and ignition wires sorted, and I'm working my way through the rest of the 280Z to GM TPI connections. When I'm finished, I'll publish the whole set so the next guy will have a better starting point. Although I'm still waiting to hear from someone who's done this before me, if only to verify my connections.

 

Keep the shiny side up.

Thanks,

Steve

[strotter]

You're in the middle of the best fun you'll ever have working on the car. I'm a fool for the detail-ee stuff like this.

 

I made a wiring diagram for my swap (originally a GM '7747 ECM into my '72). I copied a Z diagram into a graphics program, deleted the old bits, modified it more to make some room, then grafted in the ECM and related parts. Mostly I was trying to figure out the details of what went where, electrically speaking.

 

 

The above is a "low resolution" image, the high resolution is here. I don't know how readable it might be for you; if it's a problem, please email me and I'll send you a .pdf that's quite a bit clearer.

 

A couple of things to note here: the "style" of the original Z diagram and that of the newer wiring diagrams is quite a bit different. Older diagrams more-or-less showed you every wire in the car on the same page, which was slow to read but very comprehensible. Modern diagrams tend to display "systems" or groups of functionally related wiring together, with the different systems on different pages. I prefer the former, even if it's a little hard to read, as may be obvious from the image, so I just "shoved" the new style into the old. For instance, the "new" part of the diagram has wires ending in the middle of nowhere, with a note "switched 12V" at the end, indicating that "this wire goes to a source of 12V that comes on when the key is on, somewhere". Things like that. Also, the whole ECM and the related stuff is powered via an oversized "ignition" relay, which is functionally the same as the original but quite a bit heavier (a Bosch 70A, yeah I know it's overkill). An exception to this is the power leads to the relays, which I fused separately and also didn't show. Also, I put the whole (abbreviated) EFI system on a single backplane, a chunk of aluminum about 12" x 14", so I could ground it all right there, as well as get to it all easily. It was originally under the passenger seat, but has now been moved to the passenger footwell behind a "false firewall" that hinges down for access.

 

You'll surely need to create something like this for your swap, with different details, depending on how much of the Datsun wiring you choose to keep, though GM ECM's of that period are all very similar. Any questions, email, I'll try to help (though I won't promise to be prompt). Good luck and have fun.

[sstallings]

Strotter and Deja,

Thanks for the posts, and the information in them. I'm still making progress (with a little help from my friends). I designed a circuit for the 2-speed fan and ran it by the tech support guys at Painless Wiring (since I buy my components from them anyway). As it turns out, Dennis Diehl at Painless has a buddy with this fan in his streetrod, so I sent him my design, and he's critiqing it as I write this. It currently meets three of my goals, and when I have his input, I'll post an update.

 

My design is attached as a .jpg file. It supports:

1. Start the fan on low speed at ignition start/run.

2. Automatically switch to high speed when either the temperature goes over 190 degrees, OR the AC trinary switch exceed the high pressure rating of the system.

3. And restart the ignition on speed high if either is still too high (after a short shut-off period).

4. But, the one thing my circuit won't do is allow the fan to continue to run after the ignition is turned off if either the temp or AC pressure is still too high due to heat soak. Dennis should be able to help with this detail for those who want it.

 

What I'm trying to avoid is a manual switch so that I don't forget to check the guages often enough and roast something expensive unecessarily. As I move forward, I'll post as much of this stuff as people want to see. I'm still no electrician, but nothing will stop this conversion process. I'm having a blast.

Thanks,

Steve

[Dudeboy]

I am learning as well, but I have to wire the fan for a LS1 swap.

If you have not already, because you indicated Painless-I have there manual list bookmarked. Go to the bottom of the page and look at Dual fan set. It shows a lead ran to the AC as well. Good Luck

Edit: I see your lead to the AC in your attached thumbnail.

 

 

http://www.painlessperformance.com/InfoSearch/manuals.php

[sstallings]

Dudeboy,

That is a great source. I'm sure I will be scouring this site for wiring diagrams for every sub-system in my car, but, that being said, I didn't find a single circuit designed for the two-speed fan (which is consistent with what Dennis told me in his e-mail). Thanks for the new material. I'll keep working on the details and posting my findings.

Steve

[sstallings]

Guys,

I just received the attached .jpg from Painless with their additions to my basic circuit design. Now I'm confident that it will work as planned. They sell everything needed except the 2-pole 70 amp (5-pin) relay (1 reqd.) that you can get from NAPA (my plug for Painless Performance based on all the help they provided), but you can also source these components at your favorite shop.

 

We decided not to include the continue-cool-after-ignition-off circuit since this fan uses most of 70 amps on high, it would drain a battery pretty quickly. Also keep in mind that your alternator has to be up to the task of running this fan with lights, AC, radio, etc. on at the same time unders normal circumstances.

 

I have to thank Dennis Diehl and his boss Dennis Overholser at Painless for their time contributions to this circuit design. Since JTR recommends this fan, I hope a number of guys on this forum find it useful. I know I will.

Thanks,

Steve

[deja]

Looks good. Any reason why you're not using the PCM to control your fans? You can set the turn on temp for the two fans and wire the outputs to run the two speed Taurus fan. I don't think you need the slow speed fan on all the time. Mine only runs when its super hot outside and I'm stuck in traffic.

[strotter]

Any reason why you're not using the PCM to control your fans?

 

This would be an excellent way to do this - certainly the most integrated - and has the added advantage that you can "bump" the engine idle RPM when the a/c kicks on; thus you can "tune" the output of the a/c system at idle, when it's most challenging anyway. I'm as we speak (well, gradually ) installing this wiring into my ECM (a GM '7730 / Vintage Air / 2-speed Taurus).

[deja]

Make sure you add some extra wiring so when the PCM turns on the high speed winding it also turns off the low speed winding. The Taurus fan won't like having them both energized at the same time.

This is how I did my LT1:

 

 

This would be an excellent way to do this - certainly the most integrated - and has the added advantage that you can "bump" the engine idle RPM when the a/c kicks on; thus you can "tune" the output of the a/c system at idle, when it's most challenging anyway. I'm as we speak (well, gradually ) installing this wiring into my ECM (a GM '7730 / Vintage Air / 2-speed Taurus).

[strotter]

Deja, that's awesome. I'm comfortable with the digital end of things, but the actual wiring a bit out of my element.

 

So help me interpret the logic here. From cold motor, with a/c "OFF": A10 is high, A11 is high, both Primary and Secondary Coolant Fan Relays are open, the top New Relay (1) is closed, lower New Relay (2) is open; coolant temp increases to Fan 1 Enable Temp., A11 goes low firing the Primary Cooling Fan Relay. This pulls D4 up, which passes through the "Normally Closed" new relay 1 which puts high amperage current to the Taurus fan motor's "low speed" winding. Engine then gets hotter until it reaches Fan 2 Enable Temp. A10 goes low, setting the Secondary Cooling Fan Relay pulling F1 up. This triggers BOTH new relays, opening 1 (shutting off the low-speed power) and closing 2 (turning on the high-speed power) at the same moment.

 

Now, from cold motor with a/c "ON": A10 is low, A11 is high; so the Secondary Fan Relay is closed, sending current to both of new relays opening 1 and closing 2. High current goes via New Relay 2 to the fan high speed windings. Temp increases to Fan 1 Enable Temp (probably not, 'cause that fan's already spinnin' but let's say), A11 goes low dropping the Primary Cooling Fan Relay. D4 still goes high, but nothing happens beyond that because New Relay 1 is already open.

 

Is that about right?

 

[edit for clarity]: for those that don't know, A10 and A11 are ECM pins. A10 "goes off" strictly relative to engine temp - somewhere a bit above 100°C from the factory, though that can be adjusted in a variety of ways. A11 is different in that it fires under two conditions: 1) when engine temp gets even higher, such as 150°C, and 2) when the a/c is turned on. Its parameters can be edited, too. The factory setup for one of the late-90's ECMs are like this:

 

Fan 1 Delayed Run Time After Off 100 s

Fan 1 Disable Vehicle Speed 35 mph

Fan 1 Disable Temp. 104.75 °C

Fan 1 Enable Temp. 107.75 °C

Fan 2 Delayed Run Time After Off 0 s

Fan 2 Disable Vehicle Speed High A/C Pres 255 mph

Fan 2 Disable Temp. 151.25 °C

Fan 2 Disable Vehicle Speed 255 mph

Fan 2 Enable Temp. 151.25 °C

[deja]

The first part is right.

I just got my AC running. There are several connections (refrigeration temp or pressure) from a GM AC unit to the PCM that I can't wire up since I'm using a vintage AC instead of the GM AC unit. I may try to contact Vintage to see if there's a way to get to the refrigeration temp or pressure signals on their unit but I doubt if there is.

So I don't think the PCM is going to turn on the fans based on the AC inputs. Right now the PCM is not turning on the fan unless the coolant temp get to 192. It seems to work fine, even in traffic, but I don't think that is really safe for the compressor to rely on coolant temp instead of refrigeration temp or pressure to turn on the fan. So I am going to wire in another relay to turn on the low speed fan when the compressor clutch is engaged. I will use the clutch enage signal to active this relay's coil. +12v from this relay will be wired to the input on the NC contact on the low speed fan relay so the low speed fan will turn on either when coolant temp gets to 192 or the compressor clutch is engaged.

Like this:

[strotter]

Deja, I believe their trinary pressure switch does this. Check here.

BTW, I think we hijacked this thread. Sorry Steve.

[deja]

Funny you should mention that. While we were charging the system today I read about the trinity switch in the instructions. Too bad I bought the binary switch. I remember asking them about trinary vs binary but I had no clue at that time what he was taking about. Oh well, its charged and working now, maybe when I build the new engine I'll swap.

Also sorry about the hijacking.

 

Deja, I believe their trinary pressure switch does this. Check here.

BTW, I think we hijacked this thread. Sorry Steve.

[sstallings]

Hijacked? Are you kidding, this is great. I obviously have a 7730 ECM in my '90 TPI, but the previous owner butchered the electric fan wiring so that both fans ran all of the time, directly off the ignition through five 30 amp relays ganged together, after he had some problem he couldn't solve (probably without the manuals). It worked, but it wasn't what I wanted in my Z. I didn't know I could tap the ECM to do this, so this thread is EXACTLY what I need, since I intend to set this car up right.

Thanks,

Steve

[strotter]

I appreciate that, Steve. I'm paranoid about stepping on other people's toes, thread-wise. We're all learning new stuff all the time, and I've found it's best not to put off pertinent questions until later "Ask now, let the mods clean it up" kind of thing. If you have any '7730 (second generation) ECM questions, don't hesitate to start a thread or PM me. I'm in the middle of some of this stuff myself (have been for a couple of years, to tell the truth).

[sstallings]

strotter,

You probably can clear up a misunderstanding I have about the ECM circuit above. It states that I should use A10 and A11 to trigger my cooling relay circuit. But, the CTS is wired to C10 and A11 (in the 5.0L TBI section) or GE16 and BB6 (in the 5.7L TPI section - which aren't even ECM connector pins) in the Helms GM manual. A10 seems to only be related to the VSS sensor, so I'm confused as to what A10 does in this case, or even what it is. Or am I confusing ECM connector pin-outs with some other terminology that I should be looking at in the manual? Also, the termiology suggests that htese pins go from low to high, or high to low, depending on engine conditions/sensors, but they don't act like switches which are opened or closed, so how can they activate relays?

 

The more I understand this terminology, the more I can do on my own, but I have to admit that this is nothing like simply plugging in the Accel DFI harness on my street rod, and spending all my time tuning data maps. I guess the lack of EGR, electric fans, A.I.R., VSS, etc. really simplified that process, but didn't do as much to prepare me for this one as I thought it would.

Thanks,

Steve

[strotter]

Sorry about that Steve, but the different ECMs use different pin designations. I was just going with deja's pinouts. The 7730 setup (and documentation) isn't as straightforward as deja's ECMs is. The 7730 uses GE8 (labeled "cooling fan") for the primary cooling fan. However, the secondary fan operation is more circumspect; the factory didn't use the ECM to trigger the secondary fan. Here's the relevant "factory" circuitry from a '92 TPI Camaro:

 

 

This is a pretty low-res image, but it should be readable.

 

Though it looks like it, the ECM does not turn on the secondary via BD12; they instead used a thermal switch in the block, or the a/c pressure switch, to trigger the fan. Also, BC9 at the top doesn't turn the a/c on, but only tells the ECM the a/c has been turned on (so as to kick up the idle). BD12 has (I believe, could use some clarity here) a similar function with regard to the secondary fan.

 

However, some research turned up a couple of descriptions of the pinouts indicating that another pin, F8, is indeed the secondary fan control - it had to be there, 'cause the Corvette 7727 ECM (which is a weather-tight '7730) directly activates the fan from the ECM via relay. Identifying which pin was the only problem. This is a post over at ThirdGen from an experienced ECM guy (much more so that I, and who has a gorgeous Camaro BTW) who experimented a bit and confirmed this setup. You'll need to repin your connector to gain that functionality, but it's not really a problem if you have a "pinning" tool.

 

EDIT:

Also, the termiology suggests that these pins go from low to high, or high to low, depending on engine conditions/sensors, but they don't act like switches which are opened or closed, so how can they activate relays?

 

They actually *do* act like switches, though with no moving parts. To "go high" or "pull high", a terminal provides some voltage, be it 5v or 12v or whatever - its' electrical state is at a positive potential. It's as if a switch connected to the battery is closed. What happens then depends on what it's hooked up to. To "go low", it grounds (or sometimes provides -5V or -12v or whatever), or is at a "ground state" potential. Same as the other, what happens depends on what it's attached to. When you say a transistor is "high", though, can mean either that it's held at some positive voltage *or* that it has no electrical state at all - called "floating". That's not normally done.

 

In the diagram above, for instance: if you look in the middle of the picture at the primary fan control, you'll see that the relay's low amperage connectors "D" and "F" are attached to +12V and the ECM, respectively. The +12V can't do anything until there's some place for it to "go", which is what the ECM provides when it wants the fan spinnin' - it provides a ground ("goes low" or "pulls low") for the current to flow through. Electricity flows from the 12V source (Ignition, Fan Fuse, 250 brown wire) to the relay, thence to 335 DK GRN WHT and pin E8 to the ECM. Needless to say, the computer can't handle a lot of amperage, which the relay itself handles. If the ECM *could* handle lots of power, you could just run a wire from the battery, to the fan "positive" connector, then from the fan "negative" connector to the ECM and be done.

 

A not-bad way to think of it is: there's a little switch attached to each of the pins. The computer can open or close each switch. The only thing you really need to worry about is whether the switch is attached to + or -. Really. That's enough. It's what I do. I don't know doodly-squat about transistors or impedence or heat sinks. I just have a mental picture of lots of little switches, with tiny robot fingers opening and closing them. Some are attached to ground, some are attached to the battery, some send signals to the computer. I can modify when the computer opens or closes these switches, and that's all I need to know to tune. Beyond that, my electrical thinking is along the lines of "water flowing through a pipe".

 

Also, remember that modern electrical systems are so complex that they are designed (and built and repaired) as systems. You only need to worry about one system at a time, unlike older systems with were more integrated. Deal with the one system you're interested in, get it working, then move on to the next. They are *almost* entirely independent, and can be treated as such one at a time.