Winter Chassis Re-fresh

[wixer]

Finally got the car back on the road this week. I had an issue with a water leak, which was a pinched seal between the thermostat manifold and the V bank pipe. It was a tight fit when I first re-assembled it, now I know why.







First drive to get the car MOT'd, this morning since top end rebuild. Car is noticeably smoother and more responsive, which is probably down to the cleaner, matched injectors and new correct spec spark plugs. Maybe the cleaning of the inlet manifold and attached parts also helps a tad.

[wixer]

Haven't added any updates to this thread for a while, mainly as I didn't undertake anything worthy over the winter but I think I've finally got to the bottom of an annoying electrical issue, that I've had since owning the car and a more recent electrical issue.

For three years of ownership, I've had the dash warning light come on, quite regularly, for error code 23, which is the front knock sensor. As I documented here in this thread, I replaced both knock sensors last year. Problem never went away. A few weeks ago having put the car back on the road for the summer, I started to investigate further. After a few emails to Kaz for advice etc. and doing various continuity & voltage checks at the two connector ends of the harness that connect the main ECU & knock sensor sub-harness, I found that the voltage to the front knock sensor was virtually non existent, 0.03v compared to the rear at 0.2v. The reading was the same at the ECU output. Conclusion was the ECU was faulty. Not sure where to go for repairing it, I asked a guy at work, who's the electrical specialist in one of workshops. He said he'd open it up and check the soldered joints, before I took it to a specialist ECU repairer.

He couldn't find anything significant, just some small cracks around some of the joints, so he re-soldered them anyway. He also did the same for my cooling fan control unit, as I've had the odd time where the radiator fan wasn't coming on and the temperature gauge getting a little too high for comfort. Another particularly annoying issue, as I've replaced what I thought was the cause, the coolant sensor into the engine but two years later, the problem re-occurred.

The good news is that both repairs seemed to have worked. The knock sensor warning hasn't come on in the last two journeys (it usually come on after 5 minutes of driving) and the cooling fan kicks in when it should.

The annoying thing is, I changed both knock sensors unnecessarily, keeping what I thought was the only good one and throwing the faulty one away.

I'm beginning to come to the conclusion, having had these issues and doing quite a bit of internet searching for NSX electrical issues, that the electrical units, that seem to give most issues, are mounted directly to the rear bulkhead panel and due to their ages & probable vibration issues, being closer to the engine, could be the cause of many annoying electrical problem, the main ones being, main relay, cooling fan ECU and main engine ECU issues. This is just my opinion but I shall certainly look to these areas for any future issues I might have.

[goldnsx]

It is adviseable to take the electronics boards into account when solving problems in a car of that age/usual mileage. But the NSX is built very good and quite easy to solve compared to today's cars.

I've once had a running on 5 cylinders problem in certain conditions only for about two years. Changed some of the parts you've mentioned above like engine coolant sensor, spark plugs etc. only to find out later that one of the lower injector seals got damaged during mounting the fuel rails some time back which caused a tiny air leak and messed up the air/fuel mixture in the corresponding cylinder. Problem solved, happy car, happy owner.

[Senninha]

I'm beginning to come to the conclusion, having had these issues and doing quite a bit of internet searching for NSX electrical issues, that the electrical units, that seem to give most issues, are mounted directly to the rear bulkhead panel and due to their ages & probable vibration issues, being closer to the engine, could be the cause of many annoying electrical problem, the main ones being, main relay, cooling fan ECU and main engine ECU issues. This is just my opinion but I shall certainly look to these areas for any future issues I might have.

Welcome back from hibernation Wixer ... addressing each of the boards and the main relay are actions most of us have or will complete, or in the habit of good preventative maintenance will be completing pro-actively.

Hope you get them all sorted and continue enjoying your NSX

[wixer]

As I counted my chickens a little too early in my last post/update and the dash light came on literally the following day from the post, I had to do a little more investigating, into the KS sensor issue.

This time I decided to remove the pin from the ECU connector to check the wiring to the actual pin. A little fiddly to do, especially if your eyes are over half a century old but with various magnifying lenses I managed to remove the D4 pin from the plastic connector block using some jewellery screwdrivers. (The internet providing some useful info on removing pins from a Honda OBD 1 connector). I was expecting/hoping for a poor wiring joint, or even a small piece of dust but no, it was attached as it should be. There appeared to be nothing wrong with the pin at all.

So the only thing I could conclude, after examining the pin, was either the small tension tabs perhaps being a little slack on the internal side of the pin, or they are broken and should attached at both of their ends, thus causing a poor electrical connection to the pins on the ECU. So very delicately I bent the tab slightly, so it would have more tension to the ECU PIN and snapped it back into the plastic connector housing.

So this time, a week and half has passed and the warning light has not returned, so I actually do now believe I've solved the issue. Hopefully this bit of info may help others before they perhaps spend many hours and possibly money on trying to solve a re-occuring annoying electrical problem.

Pic attached with an arrow pointing to the spring tab.

[wixer]

So about time for an up date on my on going, gradual, rebuild of my NSX. This winter I've tackled the aircon system, it having never worked since I've owned the car and the condition of the condensers & motors when I removed them 3 years ago, god knows when it did last work. Over the last couple of weeks, I've finally got the two outboard aircon condensers back together. It's taken a while, as I've managed to source some second hand motors, one second hand condenser and one new from Amayama. I'm also replacing the dryer canister with a new one, as the small window on the top of the unit shows the internals looking a pale white-ish colour, rather than completely clear.

So with a bit of luck, I'll finally have working aircon in both my Hondas this year, as I've had to replace the condenser in the S2000. I suspect the S2000 will work straight after it gets re-filled but I think there will be further work to do on the NSX system, once it gets a re-fill.

[wixer]

Thanks to Covid, I've just had a job done that I intended to do this time last year and that is having the air-con system re-gassed, now that I have a sealed system. I went to Bee Cool in Kettering this morning, as they can accommodate the old type systems & Dave the owner, is very knowledgeable on all vehicle air-con systems. I had the system gassed with RS24, as R12 basically unobtainable & illegal.

So, all well with the gassing & the system maintained the pressure, so no leaks after the partial rebuild last year.

BUT.... the compressor won't kick in. As the air-con has never worked in my ownership (5 years), the re gas was in effect, the next step in the rebuild of the air-con system. We swapped the horn & compressor relays over to check if the relay was/wasn't working but the horn worked with the compressor relay, so relay was ok.

So, my question is, where do I start next ? I don't mind replacing components but there maybe a better set of checks I can run through, to try & get to the fault that's stopping the compressor kicking in. I don't know whether the compressor actually works either, so need to get it working to see.

I'm going to do the CCU test firstly, as I suspect the issue is electrical but any other suggestions, would be appreciated.

Thanks in advance.

Cheers

[Kaz-kzukNA1]

Did the condenser fans operate?


Kaz

[wixer]

Did the condenser fans operate?


Kaz

Hi Kaz,

Thanks for replying.

Yes, the compressor fans have operated on their own (the main radiator fan didn't activate) but I'm unsure why they would, if the compressor isn't working & extracting heat from the car. What sensor is activating them ? The only thing I can think of is the Cooling Fan ECU is switching them on after looking at the wiring diagram.

I've also looked through the Workshop Manual & have followed some of the diagnostic procedures, as follows.

1. Shorted the terminals across the Triple Press Switch, Compressor did not activate. (Still want to check the Volts of the BRN/BLK wire here).
2. Checked the voltage at the PNK/ORN terminal of the Comp Clutch Relay & there is 12V, (10A fuse also good).
3. Checked the voltage at the YEL/BLK terminal of the Comp Clutch Relay & there is 10V.
4. Ran the 2 procedures for the CCU diagnostic, no issues with either of them.

Still to do.
1. Check Volts at RED wire in engine bay to Compressor & it's continuity to the Comp Clutch Relay terminal.
2. Swap the Comp Clutch Relay again with the Horn relay, to double check the actual relay is good.
3. Do the checks on Page 22-60 of the manual, for the Cooling Fan ECU.
Cheers.

[goldnsx]

Did you try 12 V directly to the comp clutch?