Electrical Diagnostic Help

[Matthew Ross]

Hey everyone,

I have a 2009 Honda Civic with 114,000 miles.

For a while now, the blower motor has had intermittent problems. Sometimes it works perfectly, sometimes it blows slowly, and sometimes it doesn’t work at all. I have a detailed troubleshooting guide for this exact issue, but I’m sort of new to electrical diagnosis. Here’s the link to the troubleshooting guide: http://civic.hondafitjazz.com/A00/HTML/11/SNB6E11K73300081060FAAT00.HTML

My question deals with the terminology. For example, step 7 says, “Connect the blower motor 2P connector terminal No. 2 to body ground with a jumper wire.” Does this mean to just check for ground on terminal 2? I’m not sure what they mean by jumper wire.

Step 12 says, “Check for continuity between the power transistor 4P connector terminal No. 2 and body ground.”

The manual is written for pros, and some of the terminology is new to me. I understand the basic principles of electrical diagnosis, like power and ground in a circuit, continuity, and how to use a multimeter. If you can shed any light on some of the steps, that would be great.

Thanks,

Matt

Topic

[Aaron]

The blower motor would appear to be ground side switched. The several cars I’ve owned have also been this way. That guide is telling you to take the 2nd pin in the 2 pin connector and jump it to ground with a piece of wire. Since the blower motor is ground side switched that would cause the blower motor to run on high regardless of the switch on the dash.

For the step 12 question; next to the 2 wire harness should be a plug which has 4 pins (this would likely be the variable speed resistor board). It’s telling you to check the 2nd wire to see if it has continuity to ground.

This guide has a bit more info and pictures and might be easier for you to follow: http://troubleshootmyvehicle.com/honda/1.7L/blower-motor-resistor-test-1

[Joe]

a jumper wire is just a piece of wire to connect two points. In this case they want you to override the control module ground and supply a known good ground to the blower motor.

from what it sounds like you’ve simply got a bad connection somewhere. if you want to save yourself some time then go through to all the connectors/ground locations indicated in the troubleshooting guide and wiggle things around with the fan running. You SHOULD run into something along the way (either a loose wire/connector or rusty ground. Something of that nature.)

[EricTheCarGuy]

You might find the information in this article I wrote helpful.

http://www.ericthecarguy.com/faq/solving-automotive-electrical-problems

Outside of that I’d be checking the blower resistor for your problem. I’d also check the connector to the blower motor itself. Hondas of that vintage had a tendency to melt the blower motor connectors for some reason. That would cause a bad connection and intermittent operation.

Good luck and keep us posted.

[Author]

Replies