Argh! The dreaded GPC again. What is the deal with Nissan GPC deterioration?
I insured the Sentra today, so I suppose I'll actually drive it soon.
I've been moving it into and out of the shop for the past couple of weeks, and I suspected that the GPs were not getting long enough glow (but only sometimes) and not getting afterglow (substantial cold misfire).
I put a 12v test light on the GP bus and found satisfactory GP glow on a cold key ON. However, if I glowed for only a couple of seconds, turned the key OFF then back ON, no
If I leave the key OFF for about forty seconds, the GPC resets and will turn on the GP Relay No. 1 when the key is ON again.
Also, no afterglow.
First step was to add an in-car glow plug indicator, and a momentary-contact pushbutton:
(click on any image for larger)
The indicator is wired to the end of the GP bus bar, so it shows actual
state of the GP bus, not just that the GPC toggled a relay somewhere.
The pushbutton provides trigger power to the GP Relay No. 1.
Next, I went chasing the "no afterglow" problem. Found the GPC:
It took a lot longer to decide that the afterglow relay on the PCB is bad, because the trigger transistor seemed to not conduct correctly with the bad relay in circuit (no idea why). I did a very fast/ugly job of rigging a spare low-current relay in, and in testing I now have afterglow
I don't think I can find a small relay that can be mounted to that PCB and still fit it all inside the black plastic case, so I'll probably de-solder it, bore a hole in the case, and glue the relay to the outside. Meanwhile, at least I know what's wrong with it.
The relay that drives GP Relay No. 1 is much larger; it's the blue box in the pic above.
For my future reference:
- GP Relay No. 1 is fed 12v+ by the GPC; conversely . . .
- GP Relay No. 2 (afterglow) has its ground completed by the GPC.
[a few minutes later]
Everyone here knows how I love RTV . . .