blazer warning lights

[Guest Recian]

I know my truck may be a bit new for this forum but Im active on the Buick reatta part of this forum and it's always been helpful. I figure somebody could help me here. I just bought an 84 Chevy S10 Blazer 2.8L V6 and it's got a warning light on ive never seen before. It's red in color and has 2 vertical lines with a line at 45 degree angle in the middle, almost looks like a throttle plate. It's at top left of the warning light cluster between the gauges. Anyone have any ideas?

[keiser31]

Automatic choke, maybe?

[Guest Recian]

Makes sense. Maybe i'll try driving it longer and getting it warmed up. It has a high idle so that could be it.

[Larry Schramm]

Might be a silly thought, but do you have an owners manual? If so did you look there to see if it tells you what it is?

[Guest Recian]

I'll be buying one on ebay today. Theyre pretty cheap. I need to figure out why the air doesnt blow out the top vents but only the defrost/foot mode. The vacuum hoses seem visually ok and the control head is working but i'll get a manual and troubleshoot it the right way.

[Guest Bob Call]

Your AC problem is probably a bad acuator that controls the air flow door.

[Guest Recian]

Makes sense. All the hoses are in tact it just seems like there's no vacuum getting to them. Is there a primary feed for the actuator from engine vacuum? I found a broken hard plastic line that comes off the pass side of the engine from a T that goes to the carburetor

[Larry Schramm]

Talked to some of my friends that were around then and they seem to think it might have something to do with oil pressure because of the way the wiring on those vehicles were done. So, do you know what the oil pressure might be on the engine? There might be a connection.

[Guest Bob Call]

AC actuator failure is quite common in GM cars and trucks. The actuator gets is vacuum from the control selector and then manually flips the control door to send the air where you selected. Check NAPA or AutoZone, etc., for a new actuator. The one for your Blazer probably fits several GM models.

[Guest Recian]

idk the oil pressure. the oil is overfull but super clean. not even residue in the dipstick. actuator sounds right but does it create vacuum? or get it from the engine?

[NTX5467]

As a general rule, when hvac air flow ONLY comes from the floor and defrost vents at the same time, it's because that is the "Default Mode" for when there is no vacuum to move the actuators to the correct position. There will be a single vacuum tap on the intake manifold which will generally supply ALL of the vacuum to run the cruise control and hvac items. In many of the cars, they used a vacuum T with what looks like a check valve that supplied the cruise control servo it's vacuum, but when it got a crack in the t-section, it would bleed off enough vacuum that the hvac functions would not get enough vacuum to operate. So . . . manually check ALL of the vacuum hose connections and t-fittings. You'll find something in there that's aged and cracked, I suspect.

We sold or got inquiries on NONE of the vacuum actuators on almost any GM vehicle. But we did sell a good deal of the vacuum t/check valves for the cruise control. You can probably more readily find them on the HELP! rack than at a dealership now.

There is also a rotary vacuum switch on the back of the a/c control panel. We sold a good deal of them. That's where the actuators get their respective vacuum, which takes the single vacuum source (usually the line from the vacuum reservoir under the hood) and sends it where the levers dictate.

The issues with hvac actuators in light trucks didn't really "heat up" until we got the electric servo motors, first on the 1988C/K trucks. If they weren't cycled reasonably often, the internal contacts would oxidize and cease to function. When the seasons would change, we got a lot of complaints about air not coming out where it needed to. Several model years later, they finally got that deal straightened out on the C/K chassis vehicles.

So, check the vacuum hose for age cracks and the vacuum ts for similar. When you get a solid vacuum source to the reservoir, everything will probably work as designed.

Regards,

NTX5467

[Guest Recian]

Thanks that's what I wanted to know about how the system works. I got my service manual in yesterday and i've got vacuum routing diagrams. Looks like i'll be pulling the dash soon anyway because there's a short on the driver side. When you slap the driver side of the dash the interior lights come on/off, the volt gauge goes to 0 (well 8 to be technical) and the flasher indicators stay on. All this happens randomly and not all at the same time. Usually i gota slap the dash to get them to come back on. It doesnt effect engine or outside lights only dash components. I think it's the headlight connector but GM made it where youve gota have 5-joint elbows to get your hands in there to get the pull knob out to get the cover off. I'll check those vacuum hose inputs when I do that. The book shows one outside the body under the hood also that links to the actuator which i'll check too before i pull the dash.