right headlight rises, but won't lower

V

Vido Peran

True Classic
The right headlight pod on my '74 X1/9 won't lower. It will rise, although a little slower than the left pod, but it will only lower if I manually turn the motor knob. Initially, the right pod would lower spontaneously after the headlights had been turned off for awhile. Then for a week, it was OK. Then the delay recurred, and now it can only be lowered manually. This intermittent and progressive deterioration may be a clue to someone.

Once, early on, the pod lowered when I tapped the fuse box under the dash. But that never worked again.

I have wiggled, removed, and re-sat as many spade connectors as I could access in the headlight compartment, and I've squirted contact cleaner on them - with no luck.

I have removed and sanded/wire-brushed 2 ground lugs and one relay housing mount on the theory that there was a bad ground, but no joy.

I have followed the shop manual diagnostic sequence, and it indicates a bad headlight motor, but headlight motors are going for around $100, now

Does this sound like a diode problem (remember, this is a '74) - the pod only goes up, not down, and only on the right side? Or does it sound like a bad relay? Or is there some ground connection for the headlight motor that I can't see?

One thing I haven't been able to determine, though: Does the motor run in reverse to lower the pod, or does it just continue in the same direction? Does anyone here know?

VidoP.
 
Sounds just like a Diode problem

Plan on changing them both, because if 1 rotted away, it's likely the other is on it's way out too.

Easy to change.
Get 1N4001 or 1N4002 (doesn't matter)
 
Here is a link to a pictorial on how to replace the diodes...

http://www.visualimpressions.ca/fiat/diodes.htm

BUT first... test the diodes.

(You may haveta cut or lift ONE lead of each diode to test them thoroughly, as I have not done this personally, so I don't know if the circuit they are connected to would nullify the test...)

1. Using a cheap HF VOM or any other VOM... select a low scale of 1KOhm or so and test the Ohmmeter to assure it reads ZERO when the leads are touched together, indicating NO resistence to current flow.

2. Now touch each one of the leads to each one of the diode's leads. In this case, it matters not which way first. Note if current flows (ZERO) or not or if the needle points towards Infinity or a very high resistance.

3. Now reverse the leads and note if the Ohmmeter readings are OPPOSITE exactly opposite of the previous test.

4. Diodes BLOCK current flow in ONE direction and ALLOW current to flow in the other. A diode FAILS when it either SHORTS OUT and allows current to flow in BOTH directions, or burns OPEN, and allows NO current to flow in either direction.

5. Stare and compare the two diodes in the failing motor... and do the same with the GOOD motor if necessary. I do not know the GOOD resistance VALUE of a good diode and you could be the first to provide us with what you see, and what the NEW ones have as well.

Bob Brown mentions the RS diodes can be either the IN4001 or the IN4002's and someone else mentioned the 1N4004's would work as well. It would be interesting to know the resistance differences between all those as well... or if they have the SAME resistance and have different CURRENT handling capabilities.

If you find that ONE is bad you might as well replace BOTH to insure the overall circuit is balanced as well.

Hopefully this helps... and pardon me if I have asked this before... but where are you in SoCal?
 
Last edited:
Thanks, guys!

Is there a way to definitely diagnose a diode problem without having to remove the motor first? This is my daily ride, and I have a feeling that replacing the diodes would be a 2-day project requiring me to set up (and take down) temporary flood lights in the condo building's carport each day.

The photo of the diodes shows a view that I haven't seen before. Is that the bottom of the motor that is shown?

Is there a good sealant commonly available (e.g. at Pep Boys, O'Reilley, AutoZone, Home Depot, etc.) that would re-weatherproof the connections and diodes afterwards?

(I live in Culver City, Calif.)

VidoP.
 
Don't cut the diodes!

You do not have to cut any diodes. Simply UNPLUG both plugs from the motor. That will open the circuit to the diodes.
Usually, the diodes fail mechanically. (The leads rot off because they are exposed)
If you find rotted leads on the diodes, replace them. Take note of the polarity! (the diode band)
You can test them with a meter as Tony describes, but without cutting. (Tony likes to cut things. :wink2: :grin: Ha!)

I recommend a 1N4001 (50PRV) or 1N4002 (100PRV) because these are close to the working voltage in use. (12V)
A 1N4004 will work but is a 400PRV diode and you don't need that high a working voltage. The 1N4004 has a higher
forward resistance. Not that it makes a whole lot of difference because these diodes feed the headlight relay
coils. (very low current)

FYI, 1N4001 thru 1N4005 are all 1 amp diodes.

Black-Tooth said:
(You may haveta cut or lift ONE lead of each diode to test them thoroughly, as I have not done this personally, so I don't know if the circuit they are connected to would nullify the test...)

Bob Brown mentions the RS diodes can be either the IN4001 or the IN4002's and someone else mentioned the 1N4004's would work as well. It would be interesting to know the resistance differences between all those as well... or if they have the SAME resistance and have different CURRENT handling capabilities.
Click to expand...
 
Vido, there is a way, but ...

You wouldn't be able to SEE what you're working on. The likelihood of a bad diode is high.
The motor is held in by three small 10mm nuts and one 13mm (if I remember correctly) attached to the (splined) swing arm.
The motor comes out pretty easy if you remove the headlight first. (3 phillips screws to remove and 3 more to loosen.)
Easy-peasy if they're not rusted in.

You can weather-proof the new diodes easily using silicon rubber sealant slathered over them.
There are several other water-proofing sealants but I'd use clear silicone.
 
Vido Peran said:
Initially, the right pod would lower spontaneously after the headlights had been turned off for awhile. Then for a week, it was OK. Then the delay recurred, and now it can only be lowered manually. This intermittent and progressive deterioration may be a clue to someone.

Once, early on, the pod lowered when I tapped the fuse box under the dash. But that never worked again.
Click to expand...

Before you go taking stuff out get a voltmeter and check some stuff, and also work through the wiring diagram for the headlights (if you're lucky, you have the owner's manual and the owner's manual still has its fold-out wiring diagram - if not, I can dig up a copy of the '74 wiring diagram for you).

Before you do anything else, disconnect the wiring connector for the left-hand(!) motor and see if that fixes the problem. If not...

The pods are commanded down by the light-blue wire out of the headlight switch, which goes to fuse N (the rightmost little one in the early fusebox).

From there, the command-down signal is carried on a gray-yellow wire that goes first to the left-hand headlight motor wiring connector and then ton to he right-hand motor. Disconnect both wiring connectors at the headlight motors, and make sure that you have voltage on these grey-yellow wires when the pods are supposed to be down. Because it is the right headlight that's not going down, it's quite possible that you have a fault in the wire from the left headlight to the right.

If you have voltage at the grey-yellow wire for the right-hand pod then you know the command-down signal is getting that far. Check for continuity between the grey and black leads to the headlight motor itself - there should be continuity except when the headlight is in the closed position (The way it works is that the grey wire to the motor is powered by the grey-yellow wire above, and the black wire from the motor goes to the grey-black wire at the connector - this grey-black wire activates the relay that turns on the motor, so the motor will run any time that the switch is powering the grey-yellow wire and the pod is not in the down position and then shut off when the pod is down. There's a diode in that circuit, so test the continuity in both directions and use a 12-volt test light - it should flow current in one direction only when the grey wire is at +12.

From here on, everything is common to the raising and lowering path, and you say the problem is just lowering, so it will be in one of the things above.
 
I googled the diodes mentioned and found
(at http://en.wikipedia.org/wiki/1N4001_and_1N5400_series_diodes)
the following ratings:

1N4001 (1 amp, 50v repetitive reverse blocking voltage)
1N5400 (3 amp, 50v repetitive reverse blocking voltage)

Seeing that the diodes are in series with fuses M and N, which are 3 amp fuses, it might be better to match that conservative fuse rating with a diode from the 1N5400 series (i.e. 3 amp diodes). Either one, in small quantities from Allied Electronics or Mouser Electronics, costs less than a dollar each.

VidoP.
 
Those will work fine

You will have no problem with the 3A diodes.
A bit overkill for operating a 50ma relay coil. :) Still, no issue.
If anything, the thicker diode leads will be more robust. :cool:
 
I have the '74 workshop manual (in the original 3-ring binder), and the electrical schematic shows 2 things on each side labeled "concealed headlight motors" - the big almost-circular symbol which is fed by 2 diodes, and the motor symbol (a circle with a small rectangle at top and bottom).

I have no idea what the almost-circular symbol represents and why it's labeled a "headlight motor". Is it some kind of forward/reverse gearbox that toggles the direction of the motor's torque to make the light pod go up or down?

Is there a chance that a dirty or eroded contact on the right "headlight motor relay" would cause the behavior I'm seeing? Something has to do the toggling of the pod direction of motion. If it's not a mechanical toggle, it's probably the relay, I would imagine.

I'm puzzled by the symbol that looks like a square wave with a foot that slides on a contact that is connected to each motor. Any idea what that does?

VidoP.
 
Vido Peran said:
I have no idea what the almost-circular symbol represents and why it's labeled a "headlight motor". Is it some kind of forward/reverse gearbox that toggles the direction of the motor's torque to make the light pod go up or down
Click to expand...

There are two things in the box labeled "headlight motor". One is the motor itself. There's no reversing gear or anything like that, because as the motor turns in one direction it first raises the headlight, the lowers it, then raises it again... If you wired the motor to run continuously, the headlight would go up and down continuously. If this doesn't make sense, disconnect the wires from the motor and try turning it by hand in one direction and just keep going after you've first raised/lowered the headlight.

The second, the thing with the diodes leading to it, is a symbolic representation of the rotary switch inside the motor. One of the two incoming wires (the two with diodes on them) is connected to the output wire except when the headlight is down; the other is connected to the output wire except when the headlight is up. The output wire goes to the relay. Put a voltage on the incoming "up" wire and it will be connected to the output wire causing the motor to run until the light is up; put a voltage on the incoming "down" wire and the motor will run until the headlight is down.

Is there a chance that a dirty or eroded contact on the right "headlight motor relay" would cause the behavior I'm seeing? Something has to do the toggling of the pod direction of motion. If it's not a mechanical toggle, it's probably the relay, I would imagine.
Click to expand...
There is no toggle; the motor runs until the headlight is in the desired position and then the relay shuts it off. Thus, a problem at the relay wouldn't cause what you're seeing: the relay is receiving the exact same inputs from the exact same wires whether we're raising or lowering. The problem has to be further upstream.

In this case, the problem could be either in the headlight-down wire between the left pod and the right, or in the connection of that wire through its diode on the right-hand motor. The diagnostic steps I suggest above will tell you which it is.
(and I'm betting on the diode).

I'm puzzled by the symbol that looks like a square wave with a foot that slides on a contact that is connected to each motor. Any idea what that does?
Click to expand...
I believe that that's a fusible link that will melt and open the circuit if the motor jams. Without it, a jammed motor could catch on fire without ever drawing enough current to blow the fuse.
 
diagnostic details:

EricH said:
Before you do anything else, disconnect the wiring connector for the left-hand(!) motor and see if that fixes the problem.
Click to expand...

I haven't tried that, but would that imply something wrong on the left side - something that would cause a malfunction on the left side? Currently, the left side works fine (up and down).

If not...
The pods are commanded down by the light-blue wire out of the headlight switch, which goes to fuse N (the rightmost little one in the early fusebox).
Click to expand...

I think you've transposed the M and N fuses and the signals they carry.

From there, the command-down signal is carried on a grey-yellow wire that goes first to the left-hand headlight motor wiring connector and then ton to he right-hand motor. Disconnect both wiring connectors at the headlight motors, and make sure that you have voltage on these grey-yellow wires when the pods are supposed to be down. Because it is the right headlight that's not going down, it's quite possible that you have a fault in the wire from the left headlight to the right.

If you have voltage at the grey-yellow wire for the right-hand pod then you know the command-down signal is getting that far. Check for continuity between the grey and black leads to the headlight motor itself - there should be continuity except when the headlight is in the closed position (The way it works is that the grey wire to the motor is powered by the grey-yellow wire above, and the black wire from the motor goes to the grey-black wire at the connector - this grey-black wire activates the relay that turns on the motor, so the motor will run any time that the switch is powering the grey-yellow wire and the pod is not in the down position and then shut off when the pod is down. There's a diode in that circuit, so test the continuity in both directions and use a 12-volt test light - it should flow current in one direction only when the grey wire is at +12.

From here on, everything is common to the raising and lowering path, and you say the problem is just lowering, so it will be in one of the things above.
Click to expand...

I've followed the diagnostic steps in the workshop manual, and they lead to:
"h. If meter reads voltage, check connector and wires from motor for defects. Check black wire under motor mounting bolt for defects. If connector and wires are good, replace motor."

I don't know where this "motor mounting bolt" is. Is it somewhere hidden and does it form a ground connection? I'd love to check it and clean it if I knew where it was.

If the wire is "good", does the "replace motor" statement imply checking the diodes?

VidoP.
 
EricH said:
. . . the thing with the diodes leading to it, is a symbolic representation of the rotary switch inside the motor. [. . . .]
(and I'm betting on the diode). . . .
Click to expand...

Or maybe the rotary switch - which the workshop manual might class as part of the motor?
BTW, what does the diode do wrong when it fails - does it conduct in both directions or does it NOT conduct in both directions?

VidoP.
 
First off, THANKS GUYS, lots of good info here, Vido...

Yur just around the corner from me and 45 miles away... (HA!)

I have a lot of folks head up my way so we can work on their cars and I have some experience with such problems. We have two Radio Shacks 3 miles away as well.

My wife is rather ill at the moment but hopefully I could assist in a week or so if you wanna make the trip. Google 20842 Benz Road in Santa Clarita for an idea. I/we could invite a few others as well and have a little get together. Mike is in Torrance and Ricardo is nearby in Anaheim... my closest Fiat Friend is 17 miles away but it useta be 50!

Call if you wish also, 661-296-7277 between 9 and 9.
 
Vido Peran said:
Or maybe the rotary switch - which the workshop manual might class as part of the motor?
Click to expand...
The workshop manual does - it's an internal part of the motor.

BTW, what does the diode do wrong when it fails - does it conduct in both directions or does it NOT conduct in both directions?
Click to expand...

There are two failure modes. One, it refuses to conduct in either direction, in which case the light will go up but not down like yours, or down but not up, depending on which diode fails.

Two, it conducts in both directions, in which case the other(!) headlight will misbehave.
 
Last edited:
EricH said:
The workshop manual does - it's an internal part of the motor.
Click to expand...
<groan> So it may be a diode OR a bad rotary switch that the diagnostic sequence indicates as a motor problem.

There are two failure modes.
One, it refuses to condict in either direction, in which case the light will go up but not down like yours, or down but not up, depending one which diode fails.
Two, it conducts in both directions, in which case the other(!) headlight will misbehave.
Click to expand...
OK, that's why you said to first check by disconnecting the LEFT motor electrical connector (connector C19). I'll try that since it's the easiest thing at this point to do.

Thanks for all your help! I'll report back if I solve this problem.

VidoP.
 
It's the diode. It's always the diode.

You say it's your daily driver. Surely someone in your neighborhood has a box full of used motors that could sell you one for cheap. Then, just plug it in and try it. If it appears to work swap it in and replace the diodes in the removed motor at your leisure for when the other motor gives you trouble.

I'd sell you one but since you are in X1/9 heaven someone local should be able to save you the postage.
 
Yeah... "replace motor" is short-hand and "dealer-ize" for...

check the diodes and replace as necessary.

(Back in the day that was all that usually went wrong with Alternators as well, as regulators were external. Most of the alternators as well as most motors like this are fairly robust... and like most others say here on the board... its the DIODES!)

Alas... your shop manual has had you do much of what Eric suggested as well as test the GROUND leads. I had an experience many years ago where one light rose and operated correctly and the other continued up and down. I never knew if it was a light bulb or headlamp or ground wire or fuse as I "wholesaled" all the electrics and fuses and bulbs and replaced and cleaned them all as necessary. When I was done... everything worked! TA-DAAAA!

I dunno if this is a recent failure for you or that you are doing a full or partial restoration. If its just recent... I think its time for you to pull the motor and remove the headlamp first as BB noted. If its a full resto, then I suggest cleaning and insuring all ground leads and blossoms are good as well as all the lamps. They all interplay and interact with each other.

Again... I can help... per my previous post... and Mike Moiso (MIKEMO90) will probably have some parts as well as our PRO venders if needed. I know of no one in the lower SoCal region outside of Mark Allison and possibly Jeff Stich.

HTH... You've got the ball...
 
You must log in or register to reply here.
Back
Top