Parts for an AC system?

[Dale Greb]

Can anyone tell me what this ball is behind the battery? 1 hose goes to the intake manifold and one goes to this little device against the firewall. And then 1 hose from that device is cutoff somewhere. The truck has an aftermarket ac installed already but I'm not sure if this has anything to do with it. Any help or suggestions? Thanks!

 

[1998_K1500_Sub]

The black plastic sphere is a vacuum canister and, IIRC, it’s related to the source of vacuum for the HVAC air handler’s vacuum motors… or perhaps on earlier (pre-94?) TBI trucks it’s used for driving the EGR valve’s vacuum motor.

I’ll have to look in the service manual for specific details.

Regardless, it’s a storage device for vacuum.

That solenoid pictured on the firewall enables control of the vacuum sourced from the canister, e.g., so that it can be applied to a vacuum motor by energizing the solenoid. Evidently someone has monkeyed with the wiring on yours.

In certain designs the solenoid is driven with a pulse width modulated voltage from the ECU, so as to enable proportional control of the vacuum. This might be the case if it’s used to control the EGR.

I bet @PlayingWithTBI knows the answer.

 

[Schurkey]

WHAT VEHICLE?

 

[PlayingWithTBI]

I bet @PlayingWithTBI knows the answer.

Not really, I think the operative word is "Aftermarket". The solenoid screwed to the firewall definitely isn't OE. I don't remember that fitting in front of the distributor for vacuum (maybe for the idle control on a 7.4L?), or the old school rusted out accumulator/drier (with the little window to see liquid flowing through it) by the A/C hose on the firewall.

By the looks of it, it's probably an 87 - 91 maybe? It has the flat TPS connector where later TBIs had the round one. The EGR is operated straight off the vacuum hose from the front of the Throttle Body. Anyway, the small block TBIs didn't use vacuum for A/C controls, they were all electric motors. That's my opinion, I may be wrong (channeling Dennis Miller here)

 

[Donald Mitchell]

Probably had a vacuum actuated heater control valve... at one time.

 

[evilunclegrimace]

Not really, I think the operative word is "Aftermarket". The solenoid screwed to the firewall definitely isn't OE. I don't remember that fitting in front of the distributor for vacuum (maybe for the idle control on a 7.4L?), or the old school rusted out accumulator/drier (with the little window to see liquid flowing through it) by the A/C hose on the firewall.

By the looks of it, it's probably an 87 - 91 maybe? It has the flat TPS connector where later TBIs had the round one. The EGR is operated straight off the vacuum hose from the front of the Throttle Body. Anyway, the small block TBIs didn't use vacuum for A/C controls, they were all electric motors. That's my opinion, I may be wrong (channeling Dennis Miller here)

You are correct.

 

[1998_K1500_Sub]

Not really, I think the operative word is "Aftermarket". The solenoid screwed to the firewall definitely isn't OE.

Now that I look closely, that solenoid definitely looks add-on (I was viewing the pix on my phone earlier, couldn't see the detail).

Follow those wires from the solenoid and see if you can figure out how it might have been energized, that should give you some clue to its purpose.

Years ago on my 1974 GrandAm I did something similar to control the AC recirc motor; I added a solenoid, pulled vacuum from a port on the carb and routed it via the solenoid to the recirc motor. I energized the solenoid from a switch I added on the side of the console when I wanted recirc.