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| - | [[Transmission Controlled Vacuum Advance System]] (TCVAS) is an emission control system used starting with 1972 USA models. This system provides the vacuum advance only when the gear is in the top (4th) position, and retarded spark timing (with no vacuum advance) at other positions for complete combustion. For satisfactory performance during engine warm-up, TCVAS is disabled until the temperature warms up. | + | '''Transmission Controlled Vacuum Advance System'' (TCVAS) is an emission control system used starting with 1972 USA models. This system provides the vacuum advance only when the gear is in the top (4th) position, and retarded spark timing (with no vacuum advance) at other positions for complete combustion. For satisfactory performance during engine warm-up, TCVAS is disabled until the temperature warms up. |
| [http://datsun1200.com/modules/myalbum/photo.php?lid=14980 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14980.jpg] | [http://datsun1200.com/modules/myalbum/photo.php?lid=14980 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14980.jpg] | ||
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| [http://datsun1200.com/modules/myalbum/photo.php?lid=14973 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14973.jpg] | [http://datsun1200.com/modules/myalbum/photo.php?lid=14973 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14973.jpg] | ||
| <br>Location: Under dash, right side of car | <br>Location: Under dash, right side of car | ||
| + | |||
| + | The thermostatic switch: | ||
| + | * Conducts between 41F and 55 F as temperature rises | ||
| + | * Conducts above 34F when temperature falls | ||
| Tip: To prevent advance cut-out, leave heater off | Tip: To prevent advance cut-out, leave heater off | ||
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| [http://datsun1200.com/modules/myalbum/photo.php?lid=14984 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14984.jpg] | [http://datsun1200.com/modules/myalbum/photo.php?lid=14984 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14984.jpg] | ||
| + | |||
| + | |||
| + | In cold weather, vacuum advance is normal | ||
| + | Until car warms up... | ||
| + | |||
| + | [http://datsun1200.com/modules/myalbum/photo.php?lid=14985 http://ddgonzal.members.winisp.net/getThumb.aspx?width=400&uri=http://datsun1200.com/modules/myalbum/photos/14985.jpg] | ||
| + | <br>56-series 4-speed (LHD) | ||
| + | * Reverse lights switch | ||
| + | * Top switch (emission controlled models) | ||
| + | |||
| + | |||
| + | When current flows to the '''Vacuum Cutting Solenoid''', it cuts the vacuum advance. | ||
| + | |||
| + | If the Solenoid is disconnected, | ||
| + | vacuum advance works normally. | ||
| + | |||
| + | |||
| + | The '''Top Switch''' is normally open (allowing current). Only in top gear (4th) does it become electrically closed. | ||
| + | |||
| + | If you neglect to connect the top switch, | ||
| + | vacuum advance works normally. | ||
| + | |||
| + | So this is nearly a foolproof system. If any electrical component goes bad or is not connected, normal operation occurs. Only when every electric circuit is working does it cut vacuum advance. | ||
| [[Category:Emission Control And Tune-Up]] | [[Category:Emission Control And Tune-Up]] | ||
Revision as of 17:19, 28 December 2007
'Transmission Controlled Vacuum Advance System (TCVAS) is an emission control system used starting with 1972 USA models. This system provides the vacuum advance only when the gear is in the top (4th) position, and retarded spark timing (with no vacuum advance) at other positions for complete combustion. For satisfactory performance during engine warm-up, TCVAS is disabled until the temperature warms up.
Thermo Switch
The thermo switch is located inside the passenger compartment:
Location: Under dash, right side of car
The thermostatic switch:
- Conducts between 41F and 55 F as temperature rises
- Conducts above 34F when temperature falls
Tip: To prevent advance cut-out, leave heater off and roll down the windows.
Schematic
Both vacuum and electricity are used.
In cold weather, vacuum advance is normal Until car warms up...
56-series 4-speed (LHD)
- Reverse lights switch
- Top switch (emission controlled models)
When current flows to the Vacuum Cutting Solenoid, it cuts the vacuum advance.
If the Solenoid is disconnected, vacuum advance works normally.
The Top Switch is normally open (allowing current). Only in top gear (4th) does it become electrically closed.
If you neglect to connect the top switch, vacuum advance works normally.
So this is nearly a foolproof system. If any electrical component goes bad or is not connected, normal operation occurs. Only when every electric circuit is working does it cut vacuum advance.