i have the entire housing out, as stated when i said i tested everything on the passenger floor before reinstalling. and yes the motor is fine.

yes ive checked all fuses/circuit breakers. i already ordered 2 more transistors, and a few thermal fuses (internal part along with transistor).

pretty sure ive just blown another transistor, as it is behaving exactly as described when the transistor is blown.

and for anyone else replacing any of these parts, i suggest not putting anything back in untill you have tested it (ie: on the pass. floor). as i would have been VERY pissed if i reinstalled my housing and motor just to find it didnt work.

 

turns out after waiting for my thermal fuse(came yesterday) and transistor(came today) and installing both it was my thermal fuse. tested the new and old transistor both acted the same, did more unsoldering then re-soldering and installed the new thermal fuse. then i went out to the car still with all the crap torn out on the pass. side, plugged in the transistor assembly, and crossed my fingers...WINNING!!!!!!!!!!!! so i probably didnt even need another new transistor, instead just a thermal fuse. so for those doing this, you might as well order yourself a fuse or two from radioshack, who end up getting them from NTE eletronics anyway, part number NTE8118.

 

I have been reading the above posts trying to figure out my problem but am still confused. Working on a '88 vert, stock except an AC unit installed some years ago. has always worked fine. (AC in a vert in Canada makes a certain sense.) Followed the S5 FSM as recommended and it seems to indicate that the blower motor needs replacing. I find this hard to believe, but maybe that's just me. The connector on the motor shows 2 positive connections which makes me think it is grounded through the house. But my meter indicates the housing is a poor ground.

So, with the motor out of the car, what connection do you use to test it. If I just assume that one of the positives is some times the ground it works. If i try to ground through the motor housing, it doesn’t work. Can anyone tell me what connections to make to bench test the motor to be certain it is OK or gone south?

 

you can lay it on the floor and plug it in. the blower doesnt have to be bolted in to test it.

 

Tried this already an the blower does not respond. I am trying to isolate the problem as between the blower itself and the circuitry. So I need to test the motor on the bench, not in the car. My confusion is that both connector blades are marked positive, so where is the negative (ground) connection.

 

When you unplugged the connector to the fan housing was there not seven wires in the plug? Red/Yellow should be voltage and the Black wire is the ground.

 

Thanks for responding.
The connector is directly into the blower motor. There are only two wires: Blue-White and a Black.

 

they can both be used either way. so you can make the fan spin either way.

 

L/W is power and B is ground, the motor does not ground through the housing.

If you hook up these two terminals and the motor doesn't spin, replace the motor.
If it does spin, follow the wiring down the chain till you find out why.

 

Thanks guys. This answered the first question. The motor spins, so it must be OK. Now the hard part starts, tracking down the electrical fault. I can hear both relays close, so I am suspecting the transistor or maybe the thermal fuse. Will get on it in the next couple of days.

 

I believe the fan should blow on the highest setting w/o the need for any of the items you mentioned. W/key to on the Black/Yellow wire in the 7 wire connector should have voltage. Does it? W/the fan speed slider set to the far right the Blue/Yellow wire should have a ground. Supply a ground to this wire if you suspect it may not. The Black wire in the connector is a constant ground so check this wire also. If you suspect it is not supplying a constant ground then jumper a ground to it as well. And of course the 30 amp Heater fuse plus the 15 amp Cooling Fan fuse needs to be good.

 

In case you're unfamiliar w/some of the inner workings of what you're working on, the Heater relay receives voltage from the Heater fuse. The Green/Red wire in the connector supplies a ground to this relay. As long as the Cooling Fan fuse is supplying voltage on the Black/Yellow wire then the voltage from the Blue wire gets passed on to the Ex-Hi Relay. If the fan speed slider is then set to the far right position then the fan should work. The voltage coming out of the Ex-Hi relay runs to the Blue/White wire you mentioned as one of the two wires connected directly to the blower while the other wire, Black, is connected to the Black wire in the connector housing 7 wires.

 

guess I'll add mine in here too. Just got the A/C repaired and running, the blower was working on the full right, but now is intermittent there, sometimes blow sometimes nothing randomly, so from reading this, I am figuring the ex-hi relay is probably toggling or the solenoid in the relay is going bad.
Below the max setting, I need to check the power to the relay to determine if it is getting powered.

 

to get mine into MAX it takes some manipulation of the slider, shes a touchy bitch

 

Another revive. My blower motor is inop on all speeds. I have good power to the motor but no ground, I can jump ground to it and it works fine. These diagrams are rediculous, as far as I can tell it is supposed to have ground at all times correct?

 

yes, just run a ground to the body. boom done

 

Ya I couldnt easily find where that ground ran to so I just wired a new one. would like to find what happened to it but its cold and I need heat.

 

O.K. I'm back. being self employed means sometimes its a long time to find time. I bashed this blower motor problem around way too long and finally called in expert help. I think that multiple problems existed. We changed out the transistor. Much thanks to Hailers and nonameuser who posted a write-up on the transistor in another thread.

Changing the transistor at least got the symptoms to where we could begin to track them. We will now replace the 5-pin relay being ordered from Digi-Key. The part number is PB681-ND. I will let you know if this works. I figured while its all apart I should do preventive maintenance and replace the resistors and thermal fuse which are also known to give aggravation. I understand there to be 2 resistors. Does anyone have the part numbers for these 3 things.

The people at Digi Key were very helpful even for my small order. I will deal with them if at all possible and recommend anyone call them for help. Very friendly and informed. no I have no connection with them except to ask questions by phone. But they need more info than I can give them to determine the right part.

I would post photos but the car is at my mechanics so I can't get at it.

 

i think I posted the thermal fuse part # somewhere in here. I picked up 3 of each (fuse/transistor) just in case. im not sure what resistors you mean, but there are 2 RELAYS, one for all but max speed, and one for just MAX. and I may or may not have posted those parts numbers as well. I was able to pick mine up at my local parts store I think... its been awhile since ive done this.

 

NTE8118 is the thermal fuse part number

 

Thanks Barkz, your info confirms what I found out about the thermal fuse. I will oder it. If you could help witht the resistor part number it would be much appreciated.

The five pin relay with the part number I gave is the "all except hi" one. I have already ordered it. Where I live you have to order everything, no big centres nearby.

 

Ill see what i can find for you

 

In Post #43 I put a Digi Key part No. as PB681-ND for the blower motor relay. The part arrived today and it is NOT the right part. I called Digi Key and talked to them about the difference. Unfortunately they can not supply the part I need. I am going to reorder from RockAuto part No. RY801. There are pictures and it does match the relay I am replacing.

More delays but we will see. Sorry if any one was steered wrong on the earlier part number.

 

Since we got the blower working on high only I thought as mentioned above that it was still a transistor problem, maybe a bad solder or the thermal resistor failed. I built the test circuit on page U-33of the S5 FSM and tested the transistor assembly. It passed showing less than 10ma with switch off (actually the reading was 0) and just under 3 volts with the switch on, and motor ran just fine. That leaves me with the relay and the resistor.

I haven't order the relay yet because it seemed to be working when I examined it, but there isn't much else to try. My mechanic tells me all of the voltages from the logicon are good so it has to be in the blower assembly.

Will update when we have tried the new relay. In the meantime, if anyone has a suggestion I am listening.

 

I searched the '88 manual and found two references to a blower motor resistor. I does not seem to appear in the S5 manual and I can't find any other references to this part. I attached the pages from the 88 manual showing the resistor.