Ignition module locations ( hot temp)


What the hell are you doing ??? Crap on my lawn???


My entire ignition box was bad (wiring quite corroded), ended up buying new one from SNG. They don’t even come with capacitors anymore.

No , I’m just messing with you Carl!

Let’s see if I have this right. After doing a conversion to Fahrenheit (cos we’re simple folk down here) The amplifier was 197 degrees F when you started the engine, and went to 242 degrees F after 5 minutes. Wow.
Glad the idle stumble went away, not sure about the temperatures.

Me too!!! Not sure why, but, I am in a good mood this AM!!!

You know when you put it that way , those numbers do seem high. (According to my Ryobi) temperature gun.
We need someone else to do the same measurements on their car. Start it up wait a minute take a measurement, idle for five minutes and take another one.
I must admit, I think it was driving around with a pooched ignition module, and did not even know it.
The car runs way better, feels like more power, better idle and not sure if this is a coincidence or not, I’m in stop and go traffic in a heat wave and that temp gauge is not budging from below the N.
If I was to suggest to anyone here on this forum, pull out your module, see what it says on the bottom (not Singapore) and make sure you have a proper AC Delco (made in the USA), there I said it . No affiliation GM doesn’t pay me any royalties LOL!

Still impressively hot. The AB14 is supposedly bolted to the intake manifold to serve as a heat sink, but evidently it’s not doing too well in that regard! I guess any heat generated in the HEI module itself is conducted to the top of the AB14 case, and has to work its way from there around to the mount bosses and down into the intake manifold. Might make more sense to mount the whole thing upside down, actually – except IIRC the mount bosses on the intake manifold don’t exactly present a broad area for heat dissipation.

That finned plate is sounding more and more like a good idea.

1 Like

BTW, the reason I suggested idling for five minutes is that I believe that’s where the ignition amp gets hottest. At higher RPM it sends more energy to the spark plugs and dissipates less internally.

Of course, at idle there’s also less cooling airflow inside that intake manifold. All in all, a fan connected to the brake lights is sounding like a good idea!

1 Like

I did attach the finned GM heat sink they sent me,set up the whole thing on a couple of washers just to give a little lift and airflow. I’ll take a few more measurements tomorrow. I’m curious now to see if this makes any difference. Stay tuned for more temp measurements.

You spaced it away from the cool intake manifold?

When i measured temp of mine couple years ago it was about 160F-200F at idle.

Technically, I guess I sort of did, by thinking that a couple of washers might add a little more airflow, so it’s not sitting tight to the intake manifold but maybe some heat (or cooling ) transfer via the securing bolts.
Now you have to help me out here as I’m not a mechanical engineer. But did I miss a line or paragraph in The Book. The car runs better, the temp gauge is staying lower, but I didn’t read anything in The Book that suggests the module will actually make the car run cooler? I’m not kidding here but I gave it a serious shake down run in the middle of a heat wave followed up by stop and go traffic. The gauge did not budge.

A bad module could mess with ignition timing? If so, if it retarded the timing, that would make it run hotter. More advanced at idle runs cooler.

I would remove washers, the triangular surfaces provide much heat dissipation, and you dont want module box too high, where it may touch hood.

I built a similar heat sink on top, but i scraped off paint and used heat sink paste in between to help. I measured a 20F reduction.

1 Like

Thank you sounds like a plan, I know I’ve probably beat this one to death, but I really didn’t know what was going on

Interesting finned plate. Only cools that one spot rather than the entire top of the ig amp.

1 Like

For what its worth my old ignition module had made in Singapore on the back of the unit,


Yah kind of weird , that’s the one that came from GM with the ignition module. I just mounted it that way as one of the mounting holes lines up with the mounting bolt.
One more question though what do you suppose the air intake temperature gets down to if it’s the other source of cooling. Maybe another excuse to route the trumpets further forward up to the rail where the radiator banjo bolt is located. Sort of like the XJR setup.

To clarify, you ordered a GM ignition module and the aluminum heat sink came with it? Interesting. I ordered a GM/Delco module a couple months ago and go not such extras!

That heat sink has a unique GM number and specific application (which I’ve long forgotten, if I ever knew). I don’t think it was intended to be routinely used in module replacements. pretty cool, though (no pun intended)


Gary, on later XJS, like my 1995 6.0, the air intakes get their air from in front of the radiator rather than from within the engine bay.
I have seen on this forum where folks with older cars have engineered their own method of getting air to the engine from outside the engine bay.

My recently purchased Delco D1906 wasn’t made in the USA. I can’t remember where it was made, but it wasn’t the USA. I don’t think they’ve been made in the USA for a long, long time. The ‘990’ stamping on the module refers to the original part number 1875990, which goes back to the mid-1970s. From memory the first of several number changes was in the early 90s and I think corresponds to the substitution of beryllium with…something else. But, parts numbers also often change when a different manufacturer is contracted.

Also missing from my new D1906 was the unique grounding tab. The significance (or lack thereof) of this tab has been discussed from time-to-time over the last couple of decades. The genuine GM/Delco modules have generally been preferred over the others because they work better and last longer…and this tab was a difference that was immediately visible, setting the genuine modules apart from the multitude of replacements. But is it really important? I dunno.