Info needed: M38A1 flasher/signal unit on the steering column

[chris vickery]

Les, not sure regarding your bulb issue leaving you without dogs, guess replacing with a new one will tell.
On my CDN3, I had signals issues which took some time to figure but the main culprit was the signal switch itself, as they use an integrated circuit board which can burn out which was my case. I had a perplexing issue as I also had a signal wire which was bared in a small spot leaded to sporadic problems as it grounded out against sheet metal. May have possibly lead to the signal switch malfunction previously noted.

[rob love]

Chris

Absolutely that would be what burns out your contacts in the signal switch. Without a short in the equation, those switches will last decades. I can count on one finger how many of those switches I had to replace in the 40 years I have worked on SMP vehicles. The same is not true for the solid state flashers however. They do not like the heat, yet on several vehicles the military mounted then under the hood. The MLVW has it in very close proximity to the exhaust manifold.....poor planning in my mind on an otherwise stellar truck (in it's day). The flashers are also very much adverse to short circuits.

Wire no 460-461 (IIRC) is the power wire from the light switch to the signal controller. A wise man would put a fuse into that line of about 10 amps or less. That was an authorized modification to the M151A2 in Cdn service. At most, you should be illuminating 6 bulbs max of the 1683 trade number. That is only if you put on the 4 way flashers while towing a trailer. Those bulbs draw just over 1 amp a piece, I'm not sure what the flasher unit draws but being solid state my guess is it's negligible. The fuse will protect your signal controller as well as the flasher. Both are somewhat expensive, and both are likely going to be in US dollars when you do order one.

The first indication that you have a short will be that when you turn the signal arm, the indicator light will stay on.

As to your original question about the indicator lamp causing the lights not to work, no,that little lamp has no bearing on the remainder of the system.

[rob love]

By the way, I mentioned the 1683 bulb. They are available from NAPA under 2 different suppliers. If you order them under NAPA brand (LMP 1251) they will run you $5.77 retail or 3.73 trade price. But if you order the Trylight brand (TRL 1251) they will only run you $1.39 retail or $1.10 trade price.

Warranty on both is the same 30 days.

[rob love]

Last post......seems like I am talking to myself. While I am a bit tired today, some of these numbers I had to think twice about. Is this old age setting in??

[Bob Carriere]

.....when the warranty of the Chinese light bulbs is longer than your recall memory!!!!!

Cheers

[Wayne Hingley]

Originally Posted by rob love

Wire no 460-461 (IIRC) is the power wire from the light switch to the signal controller. A wise man would put a fuse into that line of about 10 amps or less. That was an authorized modification to the M151A2 in Cdn service. At most, you should be illuminating 6 bulbs max of the 1683 trade number. That is only if you put on the 4 way flashers while towing a trailer. Those bulbs draw just over 1 amp a piece, I'm not sure what the flasher unit draws but being solid state my guess is it's negligible. The fuse will protect your signal controller as well as the flasher. Both are somewhat expensive, and both are likely going to be in US dollars when you do order one.

Im not a "wise man", but I Installed a 5 amp fuse in my system per this same advice several months ago here: http://www.mapleleafup.net/forums/sh...use#post240252 See posts 62, 63 & 71.

[rob love]

Five it is.....I will amend my post. Thanks Wayne.

Mathematics say though that potentially 6 bulbs at an amp a piece require a 6 amp or higher fuse.

[Les Kovacs]

Thanks Rob & Chris for your answers and input....I found a 28 volt, 4.6 watt Wagner dash bulb from my local NAPA as well....I was told that the dash bulbs are the same as the turn signal bulb....bought 5 for about $1.30/each.....did I get the right bulb?

On start up, the turn signal worked for about 2-3 times-the green light flashed a few times then went out altogether....in your opinion, is it the old wiring which in places looks a bit worn, the flasher unit which is screwed high on the fire wall on the drivers side or is it the lever itself?

When the unit failed, the only thing I did 10 minutes before the failure was replace the two front orange lenses....any chances I broke or touched something wrong?

Thanks again,

les

[rob love]

I think your flasher is tired, or possibly had bad ground, but most likely is tired.

It can be replaced with a 2 prong 24 volt flasher if you have trouble finding a solid state one. The solid state flasher connection has 3 pins. Two of them are power in and flash out while the third is a ground. Install a normal flasher across the power in and flash out wires. Whether you cut your existing wires, or figure a way to tie in to the wiring is up to you.

If the lamp merely stayed on, then it would indicate a short, which is easy to find. There are 4 wires at the harness that have to do with the actual lamps. They are easy to remember....even will be for the right, and odd ofr the left. The key is number 460 and 461.

460 is front right turn
461 is front left turn
460-22 is rear right turn/brake light
461-22 is rear left tuen/brake light.

You would simply remove the connector at the signal arm, then with a multi meter set to ohms, put one wire of your meter to chassis ground and the other to the appropriate pin on the harness. Sorry, but I don't remember the abc numbers on the harness, but you can look those up on any SMP schematic easily enough. You will find the ohms reading (resistance) of each lamp will be somewhat similar. But if there is a short, you will find one wire will have a much much higher resistance or even a completely grounded condition. That will tell you what wire you are chasing.

The most common place for a short was the little wiring clips along the frame. They could eventually rub through the insulation of the harness and cause a short. Merely moving the offending clip a few inches along with a bit of electric tape would fix the problem.

I am sure whatever bulb you bought is fine.

Doubtful that changing a lense is your problem, although a lot fo the wires were pretty chewed up where they pass under the hood. As well, they will have been cut and a blue connector installed when guys would pull the engine. Far easier to do that than try and undo the little screw that held the clamploop that secured the wire. You could almost tell how many times the engine had been out by the number of crimp on connectors on those two wires.

[Les Kovacs]

Thanks Rob-I ordered a signal lever-it should be here tomorrow-if its not the problem...I will order a flasher-I guess I will keep lever as a spare. I will get back to this post if things do not work out.

Regards,

les