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Cruise Control Intermittent

jeff in co

jeff in co

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Location
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89' Blazer.

My resto work is moving along quite well so far. I'm trying to get the cruise control to work and it actually engaged slightly a few times. Problem is, it's certainly not consistent or reliable. So I'm looking for some input.

Things I've done:
- New turn signal blinker assembly with built in cruise switches
- Adjusted the brake pedal switch to be right against the stop and also the vacuum line switch at the brake pedal
- New EGR valve with new vacuum hoses

Sometimes it holds the speed (barely) and other times....nothing. When I do get it, I try to adjust to accelerate via the switch on the lever but it doesn't really do much.

Thinking the whole system was bad, I got another suction controller and electronic box from a salvage guy for $5. Have no idea if they work or not.

If it can engage in anyway, is the system salvageable? Are the 37" tires really making it hard to actually set a speed and would it interfere with the VSS module behind the instrument cluster?

Any tips would be great! Thanks!
 
I would make sure you dont have any vacuum leaks anywhere in the system of the truck. I know the CC on my truck can be a b!tch to set, but it works for the most part.
 
Try this if you can. I'm not sure of the setup on that truck.
Start the engine, take a line loose that has good vacuum on it, and hook it briefly directly to the actuator.

It should rev the engine up.
If you are hitting accelerate while driving, and it is only barely able to speed up, then you have a bind in the linkage, a leaking actuator, or poor vacuum source to the system.

Hooking a good source of vacuum directly to the actuator will tell you if its one of the first two.

When you hit accelerate, it should eventually floor the throttle if you hold it. If its not, then you need to find out why.
 
Jeff
Can you take pics of the CC components as I'm not sure that I have all on my 89 Blazer?

jeff in co said:
89' Blazer.

My resto work is moving along quite well so far. I'm trying to get the cruise control to work and it actually engaged slightly a few times. Problem is, it's certainly not consistent or reliable. So I'm looking for some input.

Things I've done:
- New turn signal blinker assembly with built in cruise switches
- Adjusted the brake pedal switch to be right against the stop and also the vacuum line switch at the brake pedal
- New EGR valve with new vacuum hoses

Sometimes it holds the speed (barely) and other times....nothing. When I do get it, I try to adjust to accelerate via the switch on the lever but it doesn't really do much.

Thinking the whole system was bad, I got another suction controller and electronic box from a salvage guy for $5. Have no idea if they work or not.

If it can engage in anyway, is the system salvageable? Are the 37" tires really making it hard to actually set a speed and would it interfere with the VSS module behind the instrument cluster?

Any tips would be great! Thanks!
Click to expand...
 
GalDemSuga said:
Jeff
Can you take pics of the CC components as I'm not sure that I have all on my 89 Blazer?
Click to expand...

When I get a chance, I'll take some shots. Here is what I've determined so far:

- Plunger unit (connected to the throttle body unit)
- Round, vacuum storage ball mounted on the driver's fender
- VSS box mounted behind the instrument cluster
- Electronic brain box, mounted inside of cab near brake pedal
- These are side by side with one another
- Vacuum release switch on brake pedal
- Brake light switch on brake pedal
 
Fordum said:
Try this if you can. I'm not sure of the setup on that truck.
Start the engine, take a line loose that has good vacuum on it, and hook it briefly directly to the actuator.

It should rev the engine up.
If you are hitting accelerate while driving, and it is only barely able to speed up, then you have a bind in the linkage, a leaking actuator, or poor vacuum source to the system.

Hooking a good source of vacuum directly to the actuator will tell you if its one of the first two.

When you hit accelerate, it should eventually floor the throttle if you hold it. If its not, then you need to find out why.
Click to expand...

On the plunger, there are two lines coming in. One is coming from the Vacuum line via the EGR valve and the other one (I think) goes to the pedal switch inside the cab. Should I just take the EGR vac line and put it on the cruise plunger line? I guess this would tell me if the plunger is working or not.
 
Cool. I will take stock. I know the plunger isnt there.

jeff in co said:
When I get a chance, I'll take some shots. Here is what I've determined so far:

- Plunger unit (connected to the throttle body unit)
- Round, vacuum storage ball mounted on the driver's fender
- VSS box mounted behind the instrument cluster
- Electronic brain box, mounted inside of cab near brake pedal
- These are side by side with one another
- Vacuum release switch on brake pedal
- Brake light switch on brake pedal
Click to expand...
 
GalDemSuga said:
Just took stock of everything under the hood. Item # 12 is only thing missing, while Item# 2 does noot go to the EGR but rather a port on the intake manifold. I need to look at setup at the brake pedal and then behind the speedo.
Click to expand...

I have an extra #12 for you. If you go see Andy Stanley sometime, I'll send it to you for free....:waytogo:

If I recall correctly, #2 does not go to the EGR directly.
 
From the picture, it looks like the plunger unit is also part of the control system.
In that case, I don't think that you can put vacuum directly to the actuator.
Some of the units I have worked on, have an actuator that is separate. The control unit controls the amount of vacuum it gets. With those, if you put full vacuum to it, it pulls in all the way.

That is a good test of the actuator and linkage. In your case, I don't think you can do that with yours.
But you have to have a good, solid, continuous supply of vacuum.

I'm not sure the EGR is the place to get it.

Also, that black ball is a vacuum reservoir that supplies vacuum when the engine is bogging. So it needs to be in the circuit also.
 
make sure that brake light switch isn't too tight up against the brake lever, could be hitting bumps and that brake pedal vibrating or whatnot enough to just bump that switch, it cancels out the CC. Suppose to be just a hair of space between the switch and brake lever.
 
4xcrazy said:
make sure that brake light switch isn't too tight up against the brake lever, could be hitting bumps and that brake pedal vibrating or whatnot enough to just bump that switch, it cancels out the CC. Suppose to be just a hair of space between the switch and brake lever.
Click to expand...

I thought I read somewhere in here that I needed the brake switch "up tight" against the brake pedal. If it wasn't tight, the CC wouldn't work. :confused:
 
eh, been awhile since i was under the dash, maybe i'm thinking of the brake light switch, thought it was all tied in together, was there a second switch fot the cruise only?
 
4xcrazy said:
eh, been awhile since i was under the dash, maybe i'm thinking of the brake light switch, thought it was all tied in together, was there a second switch fot the cruise only?
Click to expand...

Two switches....one for the brake and one for the cruise. They sit side by side to one another.
 
The Cruise Control switch under the dash is also the TCC lockup switch as well. These are to CANCEL the CC and the TCC. for the TCC and CC to work, the brake peddle needs to be up against these plungers, when you press the brake peddle it moves away from the plunger and releases the TCC and CC. The other switch is just brake light switch, ask me how I know. I just went thru this a couple weeks ago trying to get my TCC to lock up. The switches need to be as tight to the peddle as possible. How I "adjust" it is just like the TV cable. I push the plunger part up far towards the brake peddle and then press the brake peddle and let it set the plunger, this way your not pushing the plunder too far back away from the peddle. This seems to work.
 
Well, I got the thing to work!!

I swapped out the plunger unit with the used one I got from a guy for $5....presto, it works like a charm! Holds speed perfectly. Increased up and down just as it should.

One more thing to check off the list!

Thanks for all the advice.
 
Kinda late posting, but glad you got it fixed.
I had the same problem with mine and I ended up rewinding one of the coils on the back of the solenoid (plunger). When unwrapping it I found 2 breaks in the wire. First was about 5 wraps down and the other was about midway. Glad I had a spool of wrapping wire in the parts bin.:woot:
 
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