Gary Lewis Posted June 13, 2023 Share Posted June 13, 2023 I found what I'm sure is an error in the 1985 EVTM and want to make sure y'all agree. In the page below you can see that it says that Ckt 640 from the upper right is connected to the power going to the tach as well as the three gauges powered by the instrument voltage regulator. That is not the case, and other EVTMs show it differently. In fact, I've included the 1986 page below the 85 page to prove that. But am I missing something? Should I put the pic with the two red lines I've added on the 85 EVTM page? Is there a better way to show that? Link to comment Share on other sites More sharing options...
85lebaront2 Posted June 13, 2023 Share Posted June 13, 2023 Gary, you are correct, Tachometer requires a stable 12V power source, not the pulsing 5V the thermal gauges use. Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 15, 2023 Share Posted June 15, 2023 Gary, you are correct, Tachometer requires a stable 12V power source, not the pulsing 5V the thermal gauges use. The printed circuit between 1981-1986 is identical, so the 1985 EVTM is definitely in error here. The printed circuit is different for 1980, but not different where the tach circuit is concerned. That's a pretty big error not to be caught before now. Great job Gary in finding that. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 15, 2023 Author Share Posted June 15, 2023 The printed circuit between 1981-1986 is identical, so the 1985 EVTM is definitely in error here. The printed circuit is different for 1980, but not different where the tach circuit is concerned. That's a pretty big error not to be caught before now. Great job Gary in finding that. Thanks, guys. I found it as I was trying to figure out the C208 pinout for Rene recently and was quite confused when I saw that the IVR output appeared to be connected directly to battery voltage. So I did some checking and discovered that they corrected it in '86. But in looking back at the other EVTM's I find this: 1984: Doesn't even show the tach as far as I can tell. On the Ignition page it sends a signal out to it (F) and gets one back from it (E), but the tach isn't shown on the gauges page. In fact, in the Index there's an entry for Tachometer but no page #. So no "error" but an omission. 1983: The tach shows on Ignition pages 19 & 21 as well as in the Index. But not on the gauges page. So no error. 1982: Ditto 1983 1981: No entry in the Index but the tach is shown on Ignition Pg 21 and not on the Gauge page, so no error. 1980: This must have been Ford's first attempt at an EVTM as the whole book is lame. The tach is mentioned in the Index as being on Page 45. It is, but not correctly as it doesn't show power nor ground for 8 cyl going to it, but it does show the feed from the ignition module as well as ground. Anyway, the 1985 EVTM now shows the page below. Agree? Link to comment Share on other sites More sharing options...
81-F150-Explorer Posted June 15, 2023 Share Posted June 15, 2023 Thanks, guys. I found it as I was trying to figure out the C208 pinout for Rene recently and was quite confused when I saw that the IVR output appeared to be connected directly to battery voltage. So I did some checking and discovered that they corrected it in '86. But in looking back at the other EVTM's I find this: 1984: Doesn't even show the tach as far as I can tell. On the Ignition page it sends a signal out to it (F) and gets one back from it (E), but the tach isn't shown on the gauges page. In fact, in the Index there's an entry for Tachometer but no page #. So no "error" but an omission. 1983: The tach shows on Ignition pages 19 & 21 as well as in the Index. But not on the gauges page. So no error. 1982: Ditto 1983 1981: No entry in the Index but the tach is shown on Ignition Pg 21 and not on the Gauge page, so no error. 1980: This must have been Ford's first attempt at an EVTM as the whole book is lame. The tach is mentioned in the Index as being on Page 45. It is, but not correctly as it doesn't show power nor ground for 8 cyl going to it, but it does show the feed from the ignition module as well as ground. Anyway, the 1985 EVTM now shows the page below. Agree? That looks like a good correction. It also shows the original error so we can keep tract, just incase other literature may have the same or similar error. Link to comment Share on other sites More sharing options...
Gary Lewis Posted June 15, 2023 Author Share Posted June 15, 2023 That looks like a good correction. It also shows the original error so we can keep tract, just incase other literature may have the same or similar error. Thanks. Seems odd that only the 1985 EVTM had that error. But I'm glad that was the case. Anyway, yes I wanted everyone to be able to see what the EVTM originally depicted, so didn't "correct" it. Link to comment Share on other sites More sharing options...
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