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Fluid Drive Not Downshifting. What To Check?


White Spyder

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Yes Don, it works up to about 30 feet away via a 2.4 GHz ISM Band wireless transmitter. I like Fluke products!

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Yep, But hopefully you have a meter too.

With your 6 volt battery leads ground the relay base, 6 volts to the BAT terminal. Ground the "TH" terminal. Points should both close. With one volt meter  lead grounded other lead connected to "SOL" terminal- should show 6 volts.

With "TH still grounded- both points closed- use the ohm meter across "PRI" and "INT" terminals. Should show continuity.

Basically if the points close the relay probably is OK as long as the points are good and clean.

Bob

 

THanks Bob.  It has beeen a busy weekend with other Honey Do's and I have just now ben able to do the checks.  With the voltage check to the "SOL" term I and not getting the same voltage from the battery.  I guess I am SOL on this relay!

 

What now is the question.  I have been told by 2 supliers that that relay is no longer made.

 

BTW  I use Fluks too!  Air Check at work for WIFI networks and my multi meter is one as well.

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When you ground the TH terminal as I showed do the points click and close? If they do you almost have to have 6 volts at the SOL terminal unless the points are bad or a bad wire or solder joint. The points for the SOL terminal look iffy. You can easily trace the voltage flow.

Edited by Dodgeb4ya
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Too much voltage drop. There must be resistance/corrosion at the fuse and holder and or the solenoid points. Clean them well..

Edited by Dodgeb4ya
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Yes "TH" =throttle, Yellow wire circuit. Yellow wire goes from "TH" terminal on relay to Carb kick down SW and also to the Governer on the trans. Its the grounding circuit to cause the transmission kick down solenoid to function controlling downshifts .

 

"INT" relay terminal = Interupter Circuit. It's the Blue wire circuit. The Interupter SW. on trans grounds out  the ignition for a second to let trans direct speed gears pull apart for auto downshifts. A blue wire goes from "INT" relay terminal to the interupter switch on the trans.

 

"SOL" relay terminal= Solenoid circuit. It's the red wire circuit. This circuit supply's 6 volts to operate the kick down solenoid on the trans. Red wire from "SOL" relay terminal to the Trans solenoid.

 

"PRI" relay terminal=connects to the + side of the coil primary circuit to complete the ignition ground out circuit. It is a black wire circuit. Black wire from relay "PRI" to + side of ignition coil.

 

"BAT" self  explanitory. It's the green wire six volt suppy circuit. The 6 volt supply green wire can either go from "BAT" relay terminal to the negative side  of the coil or directly to the ignition switch. Either way works as there is six volts supplied at both terminals. Depends on early and late serial # cars.

You really need the 1946-8 Chrysler or DeSoto shop manual to see the proper wiring diagrams and M-5 transmission theory of operation and repairs.. The Imperial website only shows the later 1949-53 M-6 wiring circuits as far as I know which do not apply to your car.

Bob

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I did a carberator rebuild a few weeks ago and ran the engin after the rebuild but did not get it out on the road as I had to do a flush and replacement of the welch plugs. I am wondering if the piston in the kick down switch might be stuck in the up position. Would this keep it from downshifting under normal operation or does thi only come into play when the car is in high gear and overide at full throttle only?

In the film strip it talks about testing the switch by putting the car on jack stands and manually pushing the plunger. Is there a way to test without putting it up on stands? Saftey is my concern.

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If your KD switch was grounded out the trans would not even upshift. I don't think this is your problem. But to test it---pull the wire out of the KD switch. You can easily use an OHM meter to test the switch. One meter lead to ground, the other to the switch terminal. Push plunger in fully. Meter should show continuity. Release the plunger-open circuit-no continuity.

You can also eliminate this KD switch as the problem by pulling the KD wire and driving the car to see if it will now auto downshift.

Remember for the trans to downshift the solenoid on the trans needs six volts fed to it at the governer controlled proper speed to do an auto down shift. You can test for this by hooking a test light to the solenoid RED wire and drive the car and watch the speedometer to see at what speed the light comes on or goes out. Any time that test light is on the trans should be in low range or shifting down. Any time the light is out the trans is in high range.

You can also use your meter for doing these tests. A six volt meter reading means the car is in low range. No voltage reading means the trans is in high range.Simple enough.

More studying for you to do.

Edited by Dodgeb4ya
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My own experience with running the vehicle on jack-stands to check M-5 / M-6 operation is that it is okay for checking for governor operation ( points opening at 7 or 13 MPH, depending upon driving range) and to observe whether shifting piston is operating (looking through interupter-switch port).

 

Do NOT expect to get the vehicle to actually upshift while running on jack-stands !!!

 

There is not enough momentum in the drivetrain to keep-up oil pressure  in the transmission to complete the upshift unless you spin things up to about 35 mph in lower gear, and the upshift is very violent.   :eek:    DON'T TRY TO DO IT !!! :mad:

 

The only practical way to test for proper upshift is with the vehicle actually running on the road.

 

As for the carburetor kick-down, etc.  DodgeB4Ya has pretty-much said it all...

 

If you haven't already done so, you might perform a quickie-test on the solenoid:  remove from transmission, connect the insulated terminal to battery Negative, and take a jumper lead from battery Positive  (ground side) and hold it to the solenoid case (there will be some sparking).  The solenoid plunger should operate, and return when current is disconnected.

 

If the solenoid does NOT operate, that is part of your problem.

 

The voltage-drop through the relay would also be an issue... the "Load" contacts in the relay should be tungsten, and will tolerate a points file or 400 / 600 grit wet-dry paper.

 

Is the armature hinge-spring intact ?

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Well, got it!!!!! Thanks to all that helped with comments and posts. The photos were a HUGE help. What it took was a deep cleaning of all components. 60 + years of time created poor electrical connections. I also changed the oil in the Trans while I was at it.

Next project....... Re-wire the old girl. The covering is very brittle.

One mor thanks to all. This is what this group is all about.

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  • 1 month later...

Update!

Well it seems that all the work was just a temporary fix :(

Had a big local show this past weekend and the car did great on the way to the show. The return trip was a different story. I really think that the relay is the overall problem and it would not shift on the return trip.

I seem to recall that there is a company that is building solid state replacements for the other relays in the car but do not recall who they are. If you know, please reply to this. Also if you have any interest in replacing your fluid drive with a solid state on let me know as we might be able to get a group buy organized.

Edited by White Spyder
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You should not need a solid state relay. They last forever unless run on 12v or had a wiring short.

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Yes Don, it works up to about 30 feet away via a 2.4 GHz ISM Band wireless transmitter. I like Fluke products!

 

learning some interesting things on this thread. Thanks for posting your questions White Spyder.

This is my my next tool..lol.

 

Fluke 233

 

48D

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You should not need a solid state relay. They last forever unless run on 12v or had a wiring short.

Well this is still running 6 volt. I checked the wires whe I first had the issue and it seemed that when I fiddled with the relay it worked again but now it is not working again. I plan to pull it again this weekend.

Edited by White Spyder
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Relays are out there.  Before condemning the relay entirely, i would replace the sub-harness between the relay and tranny.

 

 

You can make one up out of THHN stranded wire from Lowe's, Home Despot, etc.,  matching the color-code in the shop manual, and wrapping with black e-tape, and have a respectable looking job of it.  Just make sure all your terminal lugs are SOLDERED and Heat-shrink insulated.

 

DO NOT TRUST CRIMP TERMS ON VEHICLE WIRING !   They are an endless source of gremlins and grief !   The factory soldered all its terminals, and so should we.

 

 

After my relay reconstruction, i still had intermittent shifting issues that seemed to be electrically-based,  so i whipped-up a replacement transmission harness, and that finally seemed to resolve things.

 

As a general rule of thumb, whenever you switch-on the ignition, you should hear the FD relay close.  Switch-off, the relay opens.  If you can switch the key on & off multiple times in succession, and here the relay operate each and every time, that suggests that the CONTROL side of the relay is functioning properly.

 

 

 

See where this gets you.

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  • 2 weeks later...

Installed the new harness from Rhoad Island Wire and no joy :(

I am reviewing the install connections and this thread to see if I missed something. When I turn on the ke I get no notice from the relay but when I use jumpers and apply power directly from the battery it works intermittently. Any othe ideas out there.

Edited by White Spyder
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Well, checked to see if each of the new wires was located at the correct terminal all was correct. Tried the key and no click. Tapped on the relay a few times, turned the key and "click" ! Went for a test drive and it worked as it should. Very happy and frustrating at the same time. Some thing is working intermittly and I am not sure what.

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