Troubleshooting no power at Rear Heater Blower Motor

[cky3396]

Hello again inmates...

83 SC, manual heat

I am not getting power to the connector of my rear heater blower motor when either one of (or both at same time) center heater levers are in the up position.

So far I've checked the following...

Tested for voltage at the connector with key on (car off and also car running) - No voltage on Yellow wire

Tested voltage at the three rear fuses - Top 2 fuses constant 12 volts, bottom 12 volts with key on



Tested the relay (pin 30 to battery, 85 to ground, 86 to power trigger, and 87 produces 12 volts)

Visual of the connector at Heater Motor looks good.



Visual of the Lever Switch looks good in up and down position (down, no contact - up, contact)



I'm just not quite sure how to proceed with testing. im not even sure how the lever switch is working exactly.. ive read that the contacts when touching sends ground to relay in the engine compartment (relay?)... its tough to even find where those wires are to see if they are smoked somewhere downstream to engine compartment.

any guidance would be greatly appreciated

also, yes I am familiar with back dating however I would like to remedy this situation as-is and I'll possibly entertain a backdate project in the future. I'd just like to get things working as designed

[Dpmulvan]

Originally Posted by cky3396

Hello again inmates...

83 SC, manual heat

I am not getting power to the connector of my rear heater blower motor when either one of (or both at same time) center heater levers are in the up position.

So far I've checked the following...

Tested for voltage at the connector with key on (car off and also car running) - No voltage on Yellow wire

Tested voltage at the three rear fuses - Top 2 fuses constant 12 volts, bottom 12 volts with key on



Tested the relay (pin 30 to battery, 85 to ground, 86 to power trigger, and 87 produces 12 volts)

Visual of the connector at Heater Motor looks good.



Visual of the Lever Switch looks good in up and down position (down, no contact - up, contact)



I'm just not quite sure how to proceed with testing. im not even sure how the lever switch is working exactly.. ive read that the contacts when touching sends ground to relay in the engine compartment (relay?)... its tough to even find where those wires are to see if they are smoked somewhere downstream to engine compartment.

any guidance would be greatly appreciated

also, yes I am familiar with back dating however I would like to remedy this situation as-is and I'll possibly entertain a backdate project in the future. I'd just like to get things working as designed

You don’t even need that blower. Relay circled in blue

[cky3396]

Thanks Dpmulvan, relay bench tested and is functional

[cky3396]

alright update from the lab. it is fixed, but im not entirely sure what exactly the issue was.

between inspecting, cleaning contacts, wiggling wires, rotating the base of the relay, plugging and unplugging things... the heater floor levers are now grounding pin 85 on the rear blower relay and im getting a 12.5 volts reading at the blower motor connector.

and learned a few things along the way, so thats nice.