I'm pretty sure the blower motor is blown, but I just wanted to check with you guys. Here's the story:

I started my car this morning (single digit temps of course) and when I got in the car the heater wasn't working. I can hear the relay clicking and stuff so I figure the motor's blown. I take every thing apart and such and test it per the service manuals instructions. Everything seems to check up to the manual so the next step is to check the Logicon. I skipped this because I hate taking it out. I inspected the motor housing and took out the motor. I tested it to a battery and it runs fine. So I go back to the car and plug it in there (with the heater switch on full) and sure thing the motor works. So I start putting everything back together and when I'm done I check it again. This time it doesn't work.

Now here's what happens. If I plug in the motor with the switch on full it turns on. If I then turn the switch down even the tiniest bit, the fan shuts off and I can't get it to turn back on again. The fan won't turn on unless the switch is on high. After it shuts off, when I unplug the fan I can here a relay clicking (hi speed relay) but after the fan shuts off I can't here it shut on and off when I slide the switch. When I watch the voltage at the fan plug (fan disconnected) and move the slider back and forth I can watch the voltage move up and down.

Has anybody experienced anything like this? I hope I wasn't to confusing with my explanation. Thanks in advance.

 

I'm just throwing this out there but I think you might have a ground problem. My motor wasn't working at all last year even after I replaced the logicon with a brand new one. My old one was toast and I knew it. I beat my head for days trying to figure it out. The motor, relay, resistor all worked fine just not when it was plugged in. Finally, I took it to a dealer. Half an hour later I got my car back with a little black wire running to ground in the passenger foot well. It's been working perfectly ever since. Hope this helps.

 

To check the motor itself, get under the floorboard (pass), and find the 2 biggest wires going to it. Turn your key on and set the logicon to full speed, and probe those wires with a DMM. You should see 11-13vdc. IF you do, and it doesnt blow, the motor is bad. If you dont see voltage, you have a problem in the control system before the motor.

BTW I have a tested blower motor, $35 shipped.

 

I agree with that statement and in that theory the motor is blown. However what's boggling me is that I can get the motor to run under those weird circumstances. I'm going to try the grounding like darthmookie said and maybe that'll save me the cost of a blower motor. Thanks and I'll let you know if I need the motor.

 

There are two circuits feeding the blower.
The high speed selection pulls up a seperate relay from the variable speed power.

Check the logicon connector (cold solder joints)..

 

rx7joe, what was the final solution to you blower problem? I have exactly the same problem with an 88 vert.

 

he he....

Actually I've pretty much left it alone seeing as the nice weather is around and I'm now lazier as far as troubleshouting. I switched out the logicon a while back and it now turns on as long as the lever is turned full on. Weird stuff, that's for sure. I think it's in the wiring somewhere. I'm gonna take out the logicon again and resolder it and check the wiring to the relays. I think that might be where it's at. But that means I have to get motivated to do it. So that means it'll be a while.

 

Many times it is just that the blower motors brushes have just plain worn out by now.

I had same symtoms, tore the motor down and found worn brushes- works great now!

 

I tested ina brand new motor to find I still had the same symptoms.

Greg

 

I took the blower motor apart and checked the brushes. They are fine. I also tried a new motor and had the same problem.

I tested some more and found the following:

With the blower motor disconnected and an electrical testor in its place, everything appears to work normally. As you push the slider control from left to right current starts to flow and builds up to max output. I checked this running through the blower's ground wire and connected directy to a chassis ground. Same results both ways.

With the blower connected and electrical probes wired into the power and ground tabs on the motor:

> If I active the slider from off I get nothing. No current flow at all.

> If I set the slider at max, then switch on the ignition, the blower comes on and I show current flow. As soon as I slide off of max the blower shuts down and current flow stops. It will not reactivate if the slider is pushed back to max. Again, I checked this using both the blower ground wire and a chassis ground with the same results.

It would seem something is being reset when the ignition is turned off. I can here relays clicking away when sliding the fan switch back and forth. Any chance its a relay, and if so, where are they?

 

I found the relays. If the blower motor is plugged in, only the high speed relay clicks when the slider hits the max position. If the motor in unplugged, both relays click.

If the resistor in the relay is blown, should I get full current or no current across it?

 

I'm not sure, but I also switched out the relays from a parts car with the same results, so I don't think it's the relays. Though maybe the wiring to them.

greg