Need some help - 1997 Tahoe Heater / Blower Motor

[Mean_Green]

I know you're trying to help, and probably are to someone who has a clue, which isn't me.

That shows a relay 'Energize to RECIRC' which appears to be contained in the HVAC control and which I do not see on the one I have. It also seems to show that the Recirc and AC should only work if the mode dial in in Defrost, which doesn't make sense.

The fu'tha ahead I go, the fu'tha' behind I get.

I'm going to drop it for now. I'll be near a Chevy dealer next week and will try to ask them to see if they're willing to help explain it. I just don't want to put a now actuator in only to tear it up if something else is wrong.

 

[exp500]

Pole counter looks to be Signal wire 454 in first diagram(post38). Grab connector diagrams also to find matching wires to map out circuit completely. There is enough shown for a little diagnostics, at the pulse connector shown. Do you have a signal there?

 

[Mean_Green]

Do you have a signal there?

I wouldn't have any way to determine that.


Edit: You're helping as best you can,. but I'm not fully understanding. Maybe I just need to stop asking.

 

[Mean_Green]

New actuator arrived. Center hub is plastic, not metal. Should be interesting.

 

[Mean_Green]

Not getting anywhere.

Replacement actuator rotated once and never again, not in either direction. Old actuator ... I dropped some Superglue in the cracker gear and around the gear-to-hub surface. It works in both directions and stops, but I can't tell for how long or if the motor is still driving which will probably break the glue bond someday.

New control seems to work, sort of, but still no blower. I can hear the other actuators cycling as I rotyate the temp and position knobs. Fan came on once or twice when swapping between new control and old controls, so it seems intermittent which leads me to the relay. Usually you can open a relay to check the contacts, but not on this one. They're fairly cheap, so I'll try one.

Thing is, with the relay completely removed, I can still hear a faint click when rotating the knob from Off to Low, almost as if there's another relay somewhere. Or maybe just one of the motors activating.

 

[Mean_Green]

OK, try this one on for size.

With not much else to lose, I bring the relay in the house and use a hacksaw to slice the case so I can pull the top off to examine the contacts. It's a simple SPDT relay. Contacts look slightly arced as one would expect for a high current use, but not extreme. Operate it with my fingers a few times to make sure it wasn't hung. Shrug, tape the plastic cover back on and install it. Blower works on all speeds.

Huh?

If the relay had been hung closed (arced closed), would that have prevented blower operation on lower speeds?

 

[OR VietVet]

The test will be a new relay and see what happens.

 

[east302]

The relay is energized on high speed, switching to battery voltage and bypassing the resistor.

 

[Mean_Green]

OK, so if the contacts are failing and not engaging either A2 or B2 properly, that could cause the intermittent issue. An arcing contact might provide some power some of the time, but not full power all the time.

Remember I said voltage on a meter was not steady at the purple wire to the blower regardless of position of the knob on the control. I know the blower switch was bad as shown by the melt. If the relay contacts are/were also bad, that could explain a lot of the confusing results. I said I could hear the coil engage, but that doesn't mean the contacts were moving as they should.

-------------


" I can hear the other actuators cycling as I rotate the temp and position knobs."

It doesn't appear that any of the three actuators really stop getting power. All three seem to continue to drive based on sound alone with only the key on so I can hear them. I plan on stopping at a Chevy dealer next week to see if they might know what's supposed to happen.

---------------

Plan is to put it all back together in the morning and see what happens. I ran it for a few minutes today with everything sort of hanging loose and could feel the air change outlets dash to floor and back as I rotated the vent position knob.


No indication the AC ever activated, but that's another issue that's probably beyond me.

 

[Mean_Green]

If anybody cares ....

Dealer says the actuators stay energized for about 10 minutes after the last change before being shut down. Service Writer implied the PCM was involved somehow, but I didn't press for details.