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So I have a short somewhere!! Please Help with most likely causes. The collective wits of the group will be much better than my 1/2.
71 442 Column Shift - Driving the car the other day, I noticed I did not have any turn signals. When I checked the fuse it was blown. And when I replaced it blew again.. With the key in the"on" position or with the car running, there is 12 Volts across the fuse terminal. With the key off there is .1 volts across the fuse terminals. Any chance the turn signal indicator flasher shorted internally and is causing this? I looked at the wiring I could easily get to under the car going to the front/rear turn signals plus the wires to the back up lights - all seems fine. Thanks in advance for any and all suggestions/help
Turn the key on so there are 12 volts at the fuse terminals, put a test light across the terminals. If there is a short in the circuit the light will be illuminated. Disconnect and/or move things until the light goes out, that is where the short lies. I'd start by unplugging the turn signal switch to isolate the steering column, try turning the flashers on/off, move the turn signal lever, look at the flat harness under the carpet where your heel rests, remove bulbs etc.
Internal short in the flasher..I haven't seen it but I guess it's possible if the case is metal, is grounded etc. I don't recall if the flasher interrupts ground or positive.
So, thus far, you have turned on the Hazard Flashers. The front turn signal lamps both sides illuminate, the rear turn signal lamps both sides illuminate and the rear upper level signal lamps all illuminate when the Hazard Flashers are turned ON?
If this is true, turn off the Hazard Flashers, place the turn signal in the left turn position and the right turn position. Does either the RH side or the LH side illuminate?
Can you "hear" the turn signal flasher?
Norm - Yes, With the Hazard Flashers on - both front sides illuminate and all 4 rear bulbs illuminate and flash as they should. Flasher is clicking.
As far as turn signals - Turn signal stalk in neutral postion (off). 20a fuse (dir sig-back up lights) blows within 4 seconds of turning the key to "on".
I'm down to - "Fuse OK" or "Fuse Blown" in the SM troubleshooting tree pg 12-35.
But like a lot of folks - I'm a mere amateur (and even amateur is too kind) when it comes to finding shorts.
Thanks
Last edited by dougherp; July 13th, 2019 at 02:11 PM.
So, the lamps on the turn signal circuit appear to be working at least appear not to be shorted since they are all illuminating.
The 20A fuse has the cruise control, turn signals and back lamps. It might be the turn signal flasher as suggested by Sugar Bear. But I'd try one additional test to see if you can identify the circuit for a possible short perhaps.
Remove the reverse lamp lenses and remove the bulbs in the reverse lamp housings. Examine both the bulbs and the sockets for corrosion, etc. After you've removed the reverse lamp bulbs, see if you can insert a fuse and whether the fuse does not blow. Possible one or both of the bulbs blew, shorted out, or the socket(s) have shorted out.
Anyways, as a follow-up to moving along. If you removed the back-up bulbs from the back-up sockets under the lenses in the rear bumper, if the back-up bulb sockets appear rather functional and don't appear beat to death, then installed another fuse and the fuse blew again, it's most likely going to be the turn signal flasher unit. They'll short on the inside of the flasher can sometimes. Sometimes the turn signal flasher goes out & doesn't blow a fuse, other times it does - it's a crap shoot sometimes. One thing I've noticed on several different vintage cars though is when the flash unit starts to go bad, often times there's a little advance notice - the turn signals begin to flash slower, and/or faster, or one side flashes faster or slower than the other, and then the turn signal flasher just takes a dump and goes South. Bottom line, replace the turn signal flasher unit next if the fuse keeps blowing. The turn signal flasher unit is about directly below the headlamp switch and is supposed to be mounted in a two-pronged container. Sometimes it works its way out, other times a previous owner may have changed it and didn't bother sliding it back into the prongs - either way, no biggie. It's a little gnarly to get to. I generally lay on the front floor, reach up with my hand and yank the sucker out of the prongs, then remove it. If having removed it completely out of the circuit, insert another fuse right away. If the fuse remains good, you'll know it was the turn signal flasher can.
Last edited by Vintage Chief; July 13th, 2019 at 02:58 PM.
Reason: sp
Thanks again to all who are helping, Thanks Norm for the page reference.
That said here is the update -
Changed both flashers with new ones - No Change or help Left flashers in for the following
Disconnected Turn Signal Harness - No Change left disconnected
Disconnected Back-up Switch Connector from Neutral Safety/Back-Up Switch - No Change left disconnected
Disconnected Neutral Safety Connector from Switch - No Change left disconnected
Pulled reverse lights - No Change left lights out
The good thing is I have been able to use less fuses. One fuse will last 3 attempts if I watch the fuse very carefully while I turn the ignition switch on for only a couple of seconds. Then I can see the fuse start to get hot, glow even, and if I get the ignition off quickly the fuse won't blow. So I go that going for me.
Use a simple test light or a multi-meter. One side of the fuse (input) should be getting 12V - the opposite side of the fuse should be 0V. I suspect you're getting 12V on the opposing (output) side of the fuse when there should be no voltage - indicating a short circuit on that side of the fuse (that wire).
With the IGN SW to the ON position, no fuse in the fuse holder, measure the voltage on each side of the 20A fuse holder (on each of the metal tabs which secure the fuse). On one side you should be getting 12V - on the other side you should be getting 0V (or, negligible). I suppose you could perform the same operation measuring the amperage if you want. One side should show demonstrable amperage, while the other side should demonstrate no amperage (draw). If you get voltage and a high amperage (draw) on the opposite side of the fuse, I'd suspect you have a short circuit on that side of the fuse (the other wire). If you have a simple test light, you can use the very pointed end of the test light to probe (insert into the wire) from that point where the wire leaves the fuse. You would be seeing an illuminated light (indicating 12V) where there shouldn't be any volts until you finally arrive to the point where there is no voltage (which there shouldn't be - the light will not illuminate) and that's your point of the short circuit. Does that make sense?
Last edited by Vintage Chief; July 13th, 2019 at 05:55 PM.
Ok Norm, Now it turns crazy - Checked with IGN on, Positive multi meter cable on the right side fuse box terminal, Neg MM cable grounded to body. Got 12 volts just like I expected. Then Positive cable to left side terminal (ground side) and expected to have 12v short but got zero, nada, nothing. ?????
Also checked with test light - light turned on, on the 12v side - no light on the ground side.
Last edited by dougherp; July 13th, 2019 at 06:55 PM.
Ok Norm, Now it turns crazy - Checked with IGN on, Positive multi meter cable on the right side fuse box terminal, Neg MM cable grounded to body. Got 12 volts just like I expected. Then Positive cable to left side terminal (ground side) and expected to have 12v short but got zero, nada, nothing. ?????
Huh?
The wire leading INTO the fuse is a positive wire. The wire leading OUT of the fuse is a positive wire. You only use one ground for this connection and the reading. The ground remains in one spot. Then you check the voltage on BOTH sides of the fuse holder. I'm not following you - am I missing something?
Positive cable to left side terminal (ground side) - what do you mean?
There shouldn't be 12 volts on both terminals unless a fuse is in place. Check the terminal that does not have power with an ohm meter or continuity tester and it will show a connection to ground if there is a short circuit. This is the same as putting a test light across both terminals with the fuse removed, if the light lights the there is a short to ground. Disconnect and/or move wiring until the light goes out, the short to ground is where the wiring was moved or in what was disconnected.
Power comes INTO the fuse. The fuse is rated at a certain amperage. Power runs through the fuse to the opposite side of the fuse and remains below the fuse rating (20A in this case). The opposite side of the fuse holder - with no fuse in the holder - should demonstrate no volts. You use only one known good ground to the body of the vehicle to perform this operation. The left side terminal of the fuse is not a ground - both fuse terminals are positive.
Correct, if either side of the fuse holder has continuity to ground there is a short. Put a test light across the fuse and if it lights there is a short to ground. Disconnect and/or move things until the light goes out indicating the connection to ground which should not exist, has been eliminated.
Correct, if either side of the fuse holder has continuity to ground there is a short. Put a test light across the fuse and if it lights there is a short to ground. Disconnect and/or move things until the light goes out indicating the connection to ground which should not exist, has been eliminated.
Correct, if either side of the fuse holder has continuity to ground there is a short. Put a test light across the fuse and if it lights there is a short to ground. Disconnect and/or move things until the light goes out indicating the connection to ground which should not exist, has been eliminated.
Not correct because any light bulb, solenoid coil, etc would show continuity to ground. Unplug the TCS solenoid at the transmission and see if it still blows a fuse.
Not correct because any light bulb, solenoid coil, etc would show continuity to ground. Unplug the TCS solenoid at the transmission and see if it still blows a fuse.
That's a great point, because I was reviewing the wiring schematic and the only other place I could see which might provide the short was that bloody TCS. Nice call. The OP may even have the TCS disconnected, the wire is laying about and grounding. I think it's the only other wire in that loom?
I'm looking at a 70 schematic cause I could not find a 71, assuming its the same. Only other circuit on there is a safety sentinel buzzer in the dash on this diagram, I have no clue what that is. Its a blue wire that branches off.
I'm looking at the 71 CMS and don't see any sentinel buzzer or blue wire branching off. What I do see though is that green double white stripe TCS solenoid and switch wire which feeds directly into that 20A-dir-sig backup fuse.
Sorry, I misspoke, Yes both sides are positive. For the test - IGN on, Fuse out - I have power - 12v - to the outside terminal and No volts to the inside terminal.
With the MM - I have continuity to the terminals on outside terminal and on the inside terminal of the fuse box. So it's off to find where the short is. Happy days!!
Thanks for the help
So all this with the Neutral Safety/Back-up Switch disconnected and the turn signal harness disconnected - would you agree those are not the culprit?
Norm, Are you looking at the Green double stripe that turns into a Dark Green into the TCS switch? It looks like the TCS is inside the transmission with the downshift solenoid. Is that correct?
The TCS switch itself sits on the RH side of the intake manifold next to the oil filler tube. The green double white stripe wire runs from the wiring loom to the TCS switch.
The plug is on the side of the transmission, it has 2 wires in it (1 for the tcs the other is kickdown), unplug it. The TCS solenoid is internal to the transmission. The plug is the only wiring to the trans.
Edit, I think Norm is right, the trans side of the TCS circuit is the switch and supplies the ground to the TCS solenoid on the manifold. Unplug the plug to the manifold solenoid. there are I think, 3 vacuum lines and the plug.
Ah sorry guys, I think I might be on the wrong track here. So, there were some deltas between 1970 and 1972+ model years with what I thought Eric was referring to as the TCS switch - I'm not trying to make this more confusing. In the 1971 CSM this switch is referred to as the DVCS switch (this may not be what Eric is referring to - sorry). Page 6K-12 demonstrates the DVCS switch - which is that three vacuum ports on the side, one on top, and the electrical switch located on top of the switch. I thought this name was changed in 1972 to the TCS switch but I'm probably wrong and not sure if there was one on the 1970. This gets blurry to me.
At any rate, based upon the 1971 CSM wiring diagram, the only other wire from that loom is the green double white stripe wire which runs from the DVCS switch, branches at the FLASHER, then runs to the back of the 20A dir-sig back up fuse.
So if I read correctly 6C-13 shows how to test the TCS switch. Take connector off from the side of the trans and test as per 6C-13. However, the solenoid test on the same page refers to the T.C.S. I was confused for a moment because my car has a Distributor Vacuum Control Valve (pg 6C-4) instead of the TCS. But it looks like the test is the same.
Thanks
I believe what Eric suggested is the way to go since you want to see if the fuse is going to blow - so this is easy. Don't worry about troubleshooting the switch itself at this point - determine if this circuit is causing the fuse to blow.
(1) Do you have, in fact, a DVCS located on your intake manifold?
(2) Do you have the green double white strip wire leading to the DVCS?
(3) If so, remove the wire plug, put a fuse back into the fuse holder, turn the IGN to ON and see if the fuse blows.
The TCS in the trans supplies the ground to the DVCS to operate. It only allows vacuum advance if the transmission has shifted into drive. The exception to this rule is temperature, which is why its mounted on the intake in a water passage. If the engine temp reaches a certain level it overrides the TCS and allows manifold vacuum to the distributor to cool the engine with increased timing advance.
The plug is on the side of the transmission, it has 2 wires in it (1 for the tcs the other is kickdown), unplug it. The TCS solenoid is internal to the transmission. The plug is the only wiring to the trans.
Edit, I think Norm is right, the trans side of the TCS circuit is the switch and supplies the ground to the TCS solenoid on the manifold. Unplug the plug to the manifold solenoid. there are I think, 3 vacuum lines and the plug.
Ah, that makes even more sense to me how that DVCS/TCS switch works now w/ Eric's statement. I'm calling that DVCS the switch. It isn't. The switch is actually on the trans like Eric said, the solenoid is what is located on the DVCS - now it makes sense to me what's going on with that operation. BTW, that DVCS has four vacuum lines - three ports on the side and one on the top.
Obviously, the nomenclature here is modestly confusing, since I believe these were some of the first attempts at employing this device (not sure) - they were changed moving forward. It becomes more confusing when the diagrams demonstrate various TCS solenoids in diagrams which do not match the nomenclature in the text body. Then, to find the text body demonstrates yet another diagram with an image calling the entire DVCS a Switch (Page 6K-7, Fig. 6K-10). That figure (unlike any other) actually shows the electrical plug on top of the DVCS. Yet, I believe Eric is more to the point about this. The actual switch is the TCS on the side of the transmission, what they call the DVCS is not the switch, but the actual TCS solenoid - which they for any number of reasons refer to as the switch. WTF LOL
I know one thing - I removed mine when I changed the intake manifold gasket!
Found It!! Went and looked at the DVCS. The picture is taken "after the fix". What i found was the resistor in the top of the DVCV connector had been pushed down and the 2 leads were touching causing the short. I've owned the car for 35 years and I bet I have laid the air cleaner down on top or next to the DVCV 500 times. I had it off the other day and I bet that is when it (I) squished the leads together.
Again Thanks for all the help
And so it won't ever happen again I untwisted the resistor and taped the leads.
July 12th, 2019, 07:39 PM
