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switch-pitch testing


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My '66 Skylark has the ST 300 transmission with the switch-pitch solenoid.<P>I have trouble with stalling at lights with headlights on, and especially with the a/c on. I guess that this is because the switch-pitch idle sensor switch on the throttle is no longer working.<P>OK - I figure I can connect that black solenoid wire to my stop light and trigger the high stall pitch that way. But, I'm now not sure that the solenoid works at all. <P>When I connect the switch-pitch wire to a 12V lead with the engine off, I can hear a click in the transmission. When I start the car, block the wheels, and put in in "Drive", the rpm's drop to about 475. I would expect that connecting the power lead to the switch-pitch wire would trigger high stall and raise the rpm's significantly. Nothing. No change when I put power to the solenoid wire.<P>Why would the solenoid click in the first instance, but have a no effect on the rpm's with the car running?<P>Appreciate any suggestions.<P><BR><P>------------------<BR>

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My idle is set at 625 in Neutral, then drops to about 475 in Drive (lights and a/c off).<P>I had thought that the rpm's would go back up to 625 or higher when the solenoid switched the pitch vanes to high. But, this doesn't appear to be happening...<P>------------------<BR>

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well, i dont know about the sp converter, but does your car have an idle speed increasing solenoid connected to the a/c setup? this is common in later cars, increase the throttle openning when the ac is on...<BR><P>------------------<BR>allan<BR>--------------<BR>50 special, 455/th400<BR>64 stude gt hawk, 289/auto<BR>76 poncho GP, 400/th400

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The ST300 wiring on my 65 Special had 2 different controls wired & combined in the 1 switch, one for kicking into passing gear (also a solenoid) and the SP. <BR>The kickdown only operates at WOT. The SP control is active at 1/2 throttle to WOT, or at idle.<BR>Here are some things to try:<BR>Check both solenoids at the transmission.<BR>Make sure you have 12v @ the kickdown switch.(on my Riv this power wire is orange, and its on the wiper circuit)<BR>Try disconnecting the switch from the linkage and pulling it out 3/4 of the way with engine off-key on-listen for solenoid. If you can hear it, check with engine on-RPM Change? <BR>I have a 455 with the ST400 now in the wagon. The SP converter is from Poston, 3000 stall/1100stall. I have the wiring so it can be on all the time,off all the time or switched via factory type system. you should be able to tell if its in high stall very easily. Best of luck, <P>------------------<BR>Ted Nagel <BR>65 Wildcats <BR>65 Riviera <BR>65 Special Wagon 455 <BR>70 GS Stage1 4 Speed<BR>66 Fleetwood Brougham

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Wildcat65,<P>My concern in this posting is only with the idle speed behavior. I know that my throttle idle sensor switch is defective, but I'm trying to diagnose if there is a further problem with the s/p solenoid or the transmission.<P>When I connect a 12v lead to the stator solenoid, I can hear the click. However, when the engine is running at idle, there is no change in rpm's when I make that connection.<P>I had thought that the stator would switch the vanes to high pitch and unburden the transmission to allow the engine to rev higher at idle. Is this wrong? Appreciate any suggestions.<P>

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To quote from the 1967 Service Manual: "At engine idle the stator control solenoid is activated by a signal from a switch on the throttle linkage which changes the stator blade angle from low to high. It is also energized at 3/4 throttle opening by a switch on the throttle linkage to change the stator blades from low angle to high angle."<P>Hope this helps. When I disconnect the "idle stator switch" (the one on the throttle linkage near the firewall) on my 67 Sportwagon ST400, idle speed is noticeably lower in Drive.

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Thanks, I think the problem has resolved itself.<P>With another patched test lead, I am now seeing an increase of about 50 rpm when I energize the s/p solenoid while in drive at 625 rpm.<P>So, perhaps my problem was a bad contact on my original test connection. Will now re-assemble my switch and replace the old wiring and terminals. This time, I'm going to run the idle lead off of the brake light wire, as the throttle-mounted switch was always hard to keep adjusted.<P>------------------<BR>

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Yellow,<P>I had the same problem with the SP idle switch on my '65. Lo and behold, the problem was solved when I found a '64 idle switch setup. It mounts with the throttle return dashpot and it is much easier to adjust and stays adjusted. The only problem I have so far is that it places the switch and wiring very close to the exhaust heated manifold crossover. I'll have to fabricate a heat shield for it.<P>JMC

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  • 2 weeks later...

<BLOCKQUOTE><font size="1" face="Verdana, Arial">quote:</font><HR>Originally posted by YellowLark:<BR><B>Thanks, I think the problem has resolved itself.<P>With another patched test lead, I am now seeing an increase of about 50 rpm when I energize the s/p solenoid while in drive at 625 rpm.<P>So, perhaps my problem was a bad contact on my original test connection. Will now re-assemble my switch and replace the old wiring and terminals. This time, I'm going to run the idle lead off of the brake light wire, as the throttle-mounted switch was always hard to keep adjusted.<P></B><HR></BLOCKQUOTE><BR>I have a 66 GS 401 th300 trans with switch pitch.. a guy I know ( I call him BUICK GURU ) told me to wire the switch pich solenoid to the brake lights, He tells me they did this as a mod when these cars were new, at the dealerships,he says its less complicated and more reliable. Use light brake pressure to activate high stall to help launch with high stall and prevent stalling on decell..... To test he said with engine off apply 12 volts to solinoid and listen for click ,, if it clicks it will work. I had no click so I replaced the solenoid. I dont notice any change at idle but under a load it does rev higher when applied,,,, maybe stalling is a tuning problem I have dual edelbrock 500s w/big cam and never have stalling problems..I hope this helps<BR>

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