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tachy story

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Thanek you Josh. You must be a teacher. What a great explaination. But this is the point at which the problem begins.
When the car has a + ground the spade has a - lead. When changed to - ground, a + lead on the spade. This reverses the flow to the electronics which is not good for them. Some instructions mention reversing the internal wiring but I cannot figure this part out because the case is screwed to the mechansim forming one of the contacts needed to be switched. Or am I worng in this and only the spade and ground wires needed to be switched externally? Thom, that's what I gathered from your schematics of the circuts you sent me.
All of you guys have been grest! I'm sorry to be so dense.
Rich
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you have to take it apart and reverse the internal connections too. Its very straightforward. The hardest part is getting the chrome ring off, after 30-40 years of being held on. Once the glass is off and the black ring removed, the whole gage slips out of the metal case. You then unsolder the resistor that is on the back terminal and move it to the adjacent terminal. Switch the wire that was on terminal 2 to the spade connector terminal. Then presto! -Josh
 
This is the problem with the conversion. There is no post. It utilizes the internal frame which atches to the case. TI cannot beleive there are no others with this problem. It's the original tack for a 1964 BJ8.
 
does the back of your tach look similar to this?-Josh
tachback.jpg


tachback2.jpg

the green circled part is the only thing that needs switched inside. If you had/have wires coming from the 4 brass screws, the PO was using those as grounds, they are not necessary after you convert it.

[ 01-22-2003: Message edited by: jha2297255 ]</p>
 
It is,I beleive, the same as your picture (Thanks). Several sights I found mention this internal switching between spade to post. But "I got no stinkin" post. Secondly, this is DC. You are reversing the direction of flow of electricity to capacitors. Granted it is only 12 volts, but they fry and/or malfunction. Or am I wrong? I am supprised there haven't been failures.
Rich
 
ah you are making it complicated in your mind. I did this switch from an old AH mag article. Its easy. I have my revinyled dash 90% assembled or i could take the tach apart and show you. Do you have a digital camera? Take a picture of the inside of the tach for me and i will show you what is swapped. Email me the pic if you get a chance. Pictures make it easy. -=Josh

PS capacitors, like most electrical things, are not load sensitive. i could get long winded here and go into why we have polarized plugs on lamps now, but seriously dont worry about it. It will work.

[ 01-22-2003: Message edited by: jha2297255 ]</p>
 
Tahoe healey

are you still working on this? I found a spare tach, If you are interested I can convert it to - ground and ship it, trade or? let me know. -Josh
 
Thank you all for your advise and imput. It helped me a lot. ThomP understood my concerns regarding the revers of charge to the electronics and devised a scheem that wo;rked perfectly. I now have a neg case and neg flow to the spade (as it is on positive ground). He isolated the mech from the case and supplied a tab direct to it to accept the positive lead(as the mech had with the original positive ground). Thom took his time to work this out and proformed the instalation on my tach. He went way beyond anything usual in helping me. This is what this forum is about. All he asked of me was to pass the favor on when the opportunity comes my way.
Thank you Thom and all of you how replaied.
Rich
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