brian76

My blower motor isn't working. It was a few weeks ago but doesn't now. There are 5 wires going to the switch, with the key on ACC I get 12 volts to the TAN wire in the plug, and 12 volts to the LT GRAY wire in the other plug. The other 3 have no voltage. I don't know if they would if I had them plugged on the switch itself. Could it be that the switch may be bad? Thanks

Greg

brian, the switches are usually pretty sturdy. In fact, I've never come across one that's failed. The culprit is usually the blower relay, under the hood on top of the heater box.

DB Cooper

That blower relay is easy to remove from the firewall. Pry the case tabs back a little, and the case slides right off. You'll see the two contacts at the bottom wired to the relay coil; apply 12v and see if it clicks. In fact a 9v battery should work fine to test with.
As long as the coil side works, all it needs is a little cleaning. slide a piece of fine sandpaper (or a dollar bill if you haven't got fine paper handy) between the contacts in the switch part of the relay to clean them off. Don't forget the second set of contacts that are normally closed, clean the same way. Dust off the plug contacts if needed, and it should all work nice again.

brian76

Ok, I hooked the plugs up to the switch and in the off position, I get no voltage to all 5 wires. This is also with the climate control on OFF. When I move the climate control in any other position, I always get voltage from either a wire, or a combination of wires. This tells me that the switch is good. According to Willcox, the first 3 speeds go thru the resistor, but the HIGH speed position goes thru the blower relay only thru the firewall. Well, I'm not getting anything anywhere! Just for the hell of it , I'll check the blower connections themselves, but I doubt it. If it uses just the resistor on the first 3 speeds I would get something on the HIGH speed since it only uses the relay. So this tells me that it can't be the relay or the resistor

DB Cooper

It sounds like yours is doing exactly the same thing mine was before cleaning up the relay... switch fine, no blower at any of the speed settings.

brian76

Is the relay located on the top of the A/C box in the engine compartment?

DB Cooper

The resistor assembly is right on the a/c box. The relay is mounted to the front side of the firewall (or maybe better to call it the front side of the windshield wiper cutout) just a few inches away. Metal can, two plugs going into it. Top plug is three wires, bottom one is two wires.

DB Cooper

Mine is a 78, but I'm pretty sure yours would be the same, possibly with the relay wores layed out a little different. But here's a better location reference.

DB Cooper

The way I'm reading it, you should have +12V at the center pin on the relay, and pin 2 (the normally closed position) should have +12V at all but the high blower setting. That runs through the resistors to the blower motor. Then at high setting, the switch should be sending +12V to pin 4, makes the relay click, and the relay sends that +12 from the center pin to pin 3 instead. Pin 3 should be going directly to the hot side of the blower motor. If nothing works, then jumpering 12v directly to that pin 3 position of the relay plug should make the blower motor run. If it doesn't, then I'd suspect the blower motor itself. Hope this makes sense.

brian76

I just printed everything you posted here, and will try it tomorrow. I have my car 2 miles away at the warehouse. I'll check all of this out then and let you know how it goes. Thanks, you guys are really helping me out a lot!

brian76

OK , I went to the shop and worked on the vette.I followed advice and took the relay apart, and am not getting any voltage to it ANYWHERE on any of the tabs. So I attached a jumper wire directly to the blower motor itself from the battery, and it works like a champ. I took the relay housing off and cleaned the contact. I also cleaned all of the tabs on both the relay and resistor, and still I got nothing. I dunno, something is wrong between the switch and the relay. I've had the console apart for awhile now fixing other issues such as the pwr windows, cig lighter etc, and in the process I've been twisting the climate control around a lot. I think by twisting it , I might of screwed something up around there, but all of the connectors are fastened tight the way they should be. So I'm still confused as to what the problem is, and don't know what to do next. Any ideas? Thanks

DB Cooper

Hmmm, I've got nothin... time to double check power on the blower leg at the fusebox, and chase the wire that runs to that center post of the relay.

Have you got 12v at that #4 pin on the relay when the blower is set to hjgh speed (and the slider isn't in the off position) ?

brian76

Scratch the "not getting any voltage anywhere" part That was because I had the connector plug disconnected. Duh. Look at the diagram below with the plugs connected, and this is what I really get. This was when the key was on ACC with the blower speed set on 2, and the climate control set on bi level. Thanks

DB Cooper

Boy that's strange... what's left between the resistor and the blower motor itself? It's only a couple more feet from where you know everything's functioning, to the blower that isn't...

DB Cooper

When you flip the speed on high, are you getting power on #3 and #4, and 0v on #2 on the relay?

I thought #3 from the relay ran directly to the hot side of the blower.

brian76

You're right. Only a couple of feet between the two. I just can't understand why it was working perfectly about a week ago, and now I get nothing. I've never touched anything in the engine bay area before this happened, just on the console was where I was fooling around. I'll get you an answer for your question after I get off work tonight. Thanks

Peterbuilt

brian76

A wild thing happened tonight. I voltage tested the plug itself and got voltage but then when I plugged it on the relay , I got 0 volts.This was on tab #3. They just kept changing all of the time. Then it got really weird. The relay started making a loud drumming sound like that of a snare, lots of clicks and then it stopped. I think it shorted itself out. Mind you , I never messed with any wires, and it worked perfectly about a week ago, so I didn't change anything. When I had the relay case off to clean the contact, it looked pretty ratty and old (like 42 years old). So I just ordered a new relay, and when it comes in I'll just have to see. I really think I screwed up when I was rotating the whole climate control system while I fixing the Pwr windows, Cig ltr and other things and messed it up. Well see

DB Cooper

The buzzing sound would be power intermittently getting to pin 4 (the pin thag activates the relay). I take it the switch was set to highest speed when that happened?

Take a good look at the plugs themselves, particularly the one on the switch in the console. It's possible that with all the movement, a contact could have dislodged and pulled back, or a wire may be broken in the plug. It's not really possible to fry the relay, but a fresh one certainly can't hurt.

brian76

I'll check the plugs at the switch, and switch tomorrow after work. I don't really trust the 42 year old wire leading up to those, kind of brittle from all of the years, and I'll check them thoroughly too. New relay is shipped and on the way