Vacamatic problem!

[normanpitkin]

hi,i have just had my 41 chrysler windsor with vacamatic trans rewired completely ,a problem is occurring.The car will start and drive normally except when it shifts up to 4th gear when the engine will die ,first and second are perfect shifts and the shift from third to fourth is also perfect.I think the wiring is wrong somewhere but where!!Electrician and myself are baffled and the wiring diagram isn't very helpful ,any tips? 

[rb1949]

Bite the bullet and start re-tracing wires. Especially any tranny harness. Not familiar, my M6 Prestomatic Fluid Drive is different.

The early models (M-4) operate on engine vacuum (“vacamatic”), while the later models (M-5 and M-6) operate on a combination of electric circuitry and hydraulics.

The Vacamatic name was probably used only for marketing purposes, to associate it with the vacuum-operated semi-automatic used on the 6-cylinder cars.

The solenoid on the overdrive unit is used only for the full-throttle "kickdown" function of the overdrive. A switch on the carburetor closes at full throttle and energizes the kickdown relay. A contact in the relay then closes to energize the solenoid at its "SW" terminal. A contact in the solenoid then closes, grounding the "IGN" terminal and briefly shorting the distributor ignition points to relieve the driveline torque and allow the overdrive to downshift to direct drive. If you have access to the Shop Manual, the circuitry is shown in Fig. 53 of the Transmission chapter.

 

[1949 Wraith]

I am new to the vacamatic myself, but it since the up and down shifting works the low range. It sounds like the problem might be related to the kickdown as this momentarily interrupts the ignition and is possibly sticking in interruption killing the engine.

I would try disconnecting the kickdown switch at the carb and see if that changed anything.

[Dodgeb4ya]

These diagrams shows what  electrically happens in 3rd and 4th gears....(both high and low ranges) study carefully!

[Adam]

20 hours ago, 1949 Goat said:

I am new to the vacamatic myself, but it since the up and down shifting works the low range. It sounds like the problem might be related to the kickdown as this momentarily interrupts the ignition and is possibly sticking in interruption killing the engine.

I would try disconnecting the kickdown switch at the carb and see if that changed anything.

Thank you, I have tried this and it made no difference.

[Adam]

18 hours ago, Dodgeb4ya said:

These diagrams shows what  electrically happens in 3rd and 4th gears....(both high and low ranges) study carefully!

So from this are both the Green from the ignition to 'SF' on the relay and Yellow from the ignition a switched rather than permanent live?

 

[Adam]

Hi all.  I have done the wiring on Norman's car and as he mentioned we have a problem with shifting in to 4th gear.

This evening we have tested the governor and it is working as it should - test light is on at low revs and goes out at higher revs.

I have switched power to 'SF' on the relay into the vacuum unit.  Out of the vacuum unit into the governor switch and into the interrupter switch and back to an ignition switched live.  Also in to the interrupter switch is the orange resistance wire from the distributor.  

The problem we have is a short somewhere - when the ignition is on the Governor terminal and wires to the Ignition get very, very hot.  Any ideas?

 

Thank you Adam

[Dodgeb4ya]

3 hours ago, Adam said:

So from this are both the Green from the ignition to 'SF' on the relay and Yellow from the ignition a switched rather than permanent live?

 

Depends if the governer points are open... if so no current flow (Heavy black lines show voltage flow.. light black lines no voltage)

[Dodgeb4ya]

3 hours ago, Adam said:

Hi all.  I have done the wiring on Norman's car and as he mentioned we have a problem with shifting in to 4th gear.

This evening we have tested the governor and it is working as it should - test light is on at low revs and goes out at higher revs.

I have switched power to 'SF' on the relay into the vacuum unit.  Out of the vacuum unit into the governor switch and into the interrupter switch and back to an ignition switched live.  Also in to the interrupter switch is the orange resistance wire from the distributor.  

The problem we have is a short somewhere - when the ignition is on the Governor terminal and wires to the Ignition get very, very hot.  Any ideas?

 

Thank you Adam

Your'e wiring needs to be exactly like the diagram as long as the transmission uses the diaphram type shift unit.

Also there needs to be the proper clearance between the diaphram operating lever and the shift stem ( affects the time and operation of the interrupter switch)... this kills the ignition for a split second to release torque on the gears for a downshift.

A couple more Diagrams showing kick down and shift with IGN switch turned off.....the factory 1941 or 1941-48 Chrysler/DeSoto shop manuals describe all phases of operation and trouble shooting.

Edited November 1, 2016 by Dodgeb4ya

[1949 Wraith]

Here is a Chrysler master mechanics training film on troubleshooting the 1949 hydromatic trans I think the principles of shifting are similar just activated by hydraulics.

 

[normanpitkin]

It seems the auto lite relay HRE 4001 is faulty ,would the HRS 4001 be the same?

[1949 Wraith]

14 hours ago, normanpitkin said:

It seems the auto lite relay HRE 4001 is faulty ,would the HRS 4001 be the same?

On  my 41 Chrysler my horn relay also uses a HRE 4001 relay. You might want to see if your horn has that relay and swap it out to test your shifting.

But you would think that the relay is used in the shifting in the low range, where you say shifting functions properly.

[normanpitkin]

ha! yes we swapped the relays but the horn relay didn't work at all! the HRE4001 does work but the engine ust dies when it tries to go into 4th ,am clutching at straws really!

[normanpitkin]

the horn relay is HRC 4001 and didn't work at all! It only works as a horn relay

[normanpitkin]

hi ,many thanks to all,it was the relay AND the interrupter switch was cutting off the electric fuel pump ,I think if it still had the mechanical pump it would have been a LOT easier!How could the wiring guys know it would have an electric pump ,so no blame really.

[1949 Wraith]

Great that you got things figures out was it hard finding the correct relay? Why would anyone wire an electric fuel pump to anything involved in the operation of the transmission?

[normanpitkin]

We hadnt  but the interrupter switch interrupts all the electrics and so therefore cut off the fuel ,originally it wouldn't as the mechanical pump would be unaffected! The relay was relatively easy to find ,about$40 so not too bad really ,it just took ages to find the problem.

Edited November 19, 2016 by normanpitkin

[Dodgeb4ya]

That was the three terminal relay up on the firewall above the steering column?

I had to replace one on a 42 DeSoto once.

[normanpitkin]

yes ,the one that some say interchanges with the horn relay ,it didn't on mine!

[Adam]

I had wired the electric fuel pump to the switched side of the ignition.  What happens is that at high revs, the interrupter switch cuts power to all ignition not just the coil as I assumed.  With the pump being wired to switch, power was cut to it too, just as you need it most at higher revs.....hence the reason the car died.  We wired it directly to the battery with a switch and it works fine.  That took some diagnosing!  Thanks to everyone on here that took the time to contribute.

Thinking about it the pump could be wired to the ammeter or starter solenoid.....Norm you'll have to do that with the radio unless you want The Archers to cut out during upshifts.

Cheers ears.  Adam

[Don Coatney]

32 minutes ago, Adam said:

I had wired the electric fuel pump to the switched side of the ignition.  What happens is that at high revs, the interrupter switch cuts power to all ignition not just the coil as I assumed.  With the pump being wired to switch, power was cut to it too, just as you need it most at higher revs.....hence the reason the car died.  We wired it directly to the battery with a switch and it works fine.  That took some diagnosing!  Thanks to everyone on here that took the time to contribute.

Thinking about it the pump could be wired to the ammeter or starter solenoid.....Norm you'll have to do that with the radio unless you want The Archers to cut out during upshifts.

Cheers ears.  Adam

Something does not make sense. If the interrupter switch kills everything connected to the ignition switch would you also lose power to the radio, heater fan, horn relay, starter relay, and anything else that is powered up by the ignition switch? I believe your interpreter power supply is not wired correctly or your electric fuel pump is not wired correctly. 

[Dodgeb4ya]

As Don mentioned above something still seems not right...

The factory  transmission wiring circuit does not or should not affect any other electrical accessories wired through the ignition switch. 

The ignition switch as I recall has two dedicated terminals for the transmission wiring and must be wired up correctly to the IGN switch.

The interrupter switch only grounds out the ignition points for a split second as mentioned above only to release torque on the input shaft and direct clutch sleeve for downshifts.

Also the orange wire from the interrupter switch to the distributor must be a 10 OHM resistance type wire.

[normanpitkin]

hi ,i drove the car home ,about an hours drive ,all shifts were perfect and the heater ,horn lights all worked fine.I drove the car today and again it all works ,therefore i hesitate to fix what aint busted.

[Dodgeb4ya]

If it work's all is good.