HOLDOVER SUBURBAN REAR BLOWER TROUBLE

[Bozz]

'99 Subbie...rear blower controls totally in-op on all speeds and both settings. Everything worked great for 147K miles then one day...nada air in back.

Front A/C blower works on ALL speeds just like it always has.

Checked fuses inside and under hood. OK. Checked and re-checked with a test light.

Accessed the big connector inside down by driver's side kick panel. Nothing looked hot or melted BUT I went ahead and spliced the orange wire just to be sure. No change.

Swapped the A/C relay with another relay...no change.

All 3 relays under rear panel right side rear compartment "click" when moving switch up front. I can hear the relays click.

Blower motor is good. No squeal, no hot indications. Hooked 12 volt straight from extra battery to terminals on fan/blower and it runs like new. Fan is good.

I am not getting 12 v on the plug/ wire to the rear blower with everything switched on.

Where do I go from here? I pulled the front resistor and it does not appear to be hot ever.

Rear blower resistor (underneath the rear blower motor housing) does not appear to have been hot. However, my resistor is a 3 prong plug and every parts place I checked shows an entirely different flat 4 wire plug that looks similar to the front resistor. I have scoured the interwebs and find nothing that looks like mine. Factory air, never molested. There is a part # on the resistor that I googled and it said "Discontinued". Bullshit. I don't suspect it is the resistor BUT was going to replace them anyway to chase this down.


Anyone?

EDIT: Can the front resistor prevent power going to the rear blower???

 

[east302]

Here are the diagnostics for a 1998, should be the same for a 99. I think I grabbed the relevant documents, let me know if I missed any.

Depending on if you have rear a/c and heat together, there were different tables. There’s also one for rear heat only (no a/c) but I didn’t copy that.

Auxiliary blower inoperative, a/c without heater

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Auxiliary blower inoperative, a/c with heater:

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Splice locations:

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Ground G400 location:

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[Bozz]

Fantastic, East! The test procedure should help. As for the wiring diagrams, I'll have to do some studying.

Thanks, bro and I'll report back