Electrical issues for '70 wagoneer HELP!

[bigblack'74]

I am haveing trouble with the temp gauge on a '70 waggy. I have power to the circuitboard from the ignition feed but the power is not leaving the circuit board and going to the sending unit..i want to understand how this works. Does the power come into the board on the ignition feed then go over to this "resistor"? then into the gauge and out to the sending unit, hence showing differnt levels of resistence from the sending unit which is just a variable resistor? My concern is that this "resitor" on the board isnt working. I ohmed it and it has two pos. terminals and one ground. there is no resistence from either pos. to ground. there is only 4 ohms of res. between the pos. terminals. what does this mean? I checked gauge it is good and so is sending unit i also reattached all the 10 prongs on the back of the board where all of the feds come in...i just cant get the power out of the board.

Next question..this jeep does not have a traditional stop lamp switch which is generally located under the dash and actuates when pedal is depressed. It appears to have a pressure switch on the side of the master cylinder..similar to a low fluid lite. this doesnt work either. there is a feed from the head light switch and from the horn? why would there be two feeds and if my horn didnt work would like cause brakes lights to not work? my horn button is gone..i want to bypass this if possible but i dont understand why it would have two feeds espeacially from the horn and head light switch...i hope someone can help because no temp and no brake lights suck badly thanks alot

[mark j]

I'm assuming that the '70 has the same printed circuit that my '72 has. Try grounding the sending unit- if the gauge works you may need to check the engine ground strap at the motor mount. If not you will need to test the circuit board. The ten printed circuit pins you described are labled starting at the twelve o'clock position A, B, C, D, E in a clockwise direction- there is a gap after E after which they resume- G, H, J, K, and L(as viewed looking directly at the back of the board). The sending unit for your temp guage feeds into the A terminal- this is a blue wire with a yellow tracer stripe. In the case of my jeep this was the problem- the wire had become disconected in the wireing harness from the sending unit to the panel- you may want to see if going directly from the sending unit to the A pin (or blue/yellow wire as it enters the cluster) helps. This can also be tested by removing the printed circuit, grounding the CVR terminal on the left( the instrument voltage regulator on the far left of the printed circuit board), connect a four amp fused jumper wire from the K pin to the ignition feed, ground the output side of the temp guage (sender unit wire post on the temp gauge which is on the right and feeds via the printed circuit to the A pin) with a tester with one lead and the other to a known ground. With the ignition on- if the gauge works then you have an open circuit in the sending unit wire or in the feed wire to the K terminal. If the guage does not work it is defective. Proper function of the guage reads 72 Ohms at 100 deg, 23 Ohms at 161 deg, and 9 Ohms at 250 deg- hope this helps.
With respect to your brake lights- my PO ( and a good one at that) used a after market switch at the pedal to detect depression of the pedal- very reliable.

[bigblack'74]

I have checked the blue and yellow wire and it is still togther connects like it should to the a pin. the power is getting to that odd three pronged box resister thing but the power doesnt seem to come out of there..is that the voltage regulator for the board? i am notseeing any reason why it wont go out thru it. there is 12.45 volts to that spot on the board..the power isnt evening getting to the gauge?...do u know where or any part number for that brake light switch? i need something badly thanks alot

[mark j]

Don't know about a part number- may be available in the Help section of NAPA's, Autozone, Checker or such. Does your fuel gauge work- it too is dependent on the voltage regulator. If the fuel guage works then your problem most likely lies in the printed circuit itself with respect to the temp guage or the sending unit loop- try cleaning the terminals on the guage to see if this helps. Short of this you will have to isolate the guage by getting 12V in at the K pin, grounding the voltage regulator and grounding the sending unit at the A post via a tester to isolate the problem better- IE printed circuit, sending unit circuit, voltage regulator, or guage. Hope this helps.

[Tad]

I doubt your brake lights are dependent on anything, they should work with the ignition off just by pressing the pedal. My 70 brake lights did nothing when I got it.
Pulled off the connector and shorted it across with a jumper wire, lights were fine.
Installed new sender unit from Auto Zone (had to get the one from a 70 J Truck, no wag listed) and all was fine. I did have to install some push on type connectors as the one from AZone was not the plug connector, and rebleed the brakes as removing the sender lets in a small amount of air.

Other than that I can't help as I junked the H2O and Oil sending units in favor of mechanical ones.

[ November 17, 2002, 08:07 PM: Message edited by: tadsal ]

[dharmabum]

Heres a link for a brake light pressure switch.
http://www.speedwaymotors.com/product.asp?strBase%5FList=&hilt=&source=&base%5Fno=91031305&str%5Fbase%5Fno=91031305%2C&header%5Ftitle=Keyword+Search&page%5Fname=search%2Fkeyword%5F
Its for street rods but I plan on using it on my 72 Commando and my 72 Wag if/when the one on it goes bad. I know there is some sort of voltage reducer for all the gauges in those early panels. I yanked out the one in my Commando cause I am putting in real gauges, etc... and the Wag one works fine so far but if I remember correct there is a voltage reducer of some sort that everything must go through for the panel. Perhaps that is where your problem is? when you tested the panel did you run a full 12 volts through as I have heard this can short the board. there is a post concerning this on the AJC BBS at http://www.off-road.com/jeepster/ Try searching around on there for info on the printed circuit dash panels.