Automotive Air Conditioning Information Forum (Archives)

Provided by www.ACkits.com

We've updated our forums!
Click here to visit the new forum

Archive Home

Search Auto AC Forum Archives

High blower speed doesn't work Pages: 12Last

DABA78 on Wed January 09, 2008 9:13 PM User is offline

Year: 1978
Make: Oldsmobile
Model: Cutlass Supreme
Engine Size: 260 c.i.
Refrigerant Type: R134a
Country of Origin: United States

Hello!

The highest blower speed on my '78 Olds Cutlass doesn't work. It hasn't worked for quite a while, but now that the windshield gets frosty overnight, it really makes a difference how long the defroster takes to clear it up!

I have a factory service manual for the car, and it looks like the blower switch is a 4-speed one. As I mentioned, the lower 3 speeds all work. The manual also shows that the contact for the high speed of the switch is connected to what is referred to as a "high-blower relay." (I can see the relay, located under hood near blower motor).

The schematic diagram shows that the lower 3 speeds are controlled by a group of resistors, and that the high speed looks like it is connected to a coil within the relay.

Has anyone had any experience with these relays? I originally thought that the blower control switch was bad, but when I saw by the schematic that the high speed relies on a relay, I began to suspect a faulty relay instead. I wondered how to test the relay.

Any input welcome!

Chick on Wed January 09, 2008 9:25 PM User is offlineView users profile

I can't remember off hand which relay it is, but if you have manual AC then yes, you have a high speed fan relay (blower motor relay) If you have ATC then it's a module.. So you have a fan switch that you can choose the fan speed? Then it's manual.. AcDelco part number 15-8166
Here is a list of cars that use this relay so the easiest thing would be to find a used one to try, then either confirm and buy a new one, or begin looking at the wiring..Hope this helps..

PS: here is an image of the relay courtesy of AcDelco..

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

Chick on Wed January 09, 2008 9:46 PM User is offlineView users profile

BTW, you might try unplugging the relay and cleaning the terminals, last one I had i had to keep wiggling the plug due to corrosion on the connection..Depends on how dirty they get...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

DABA78 on Wed January 09, 2008 9:46 PM User is offline

Thanks for the quick response, Chick!

I've just been on the O'Reilly Auto Parts Website, and found that they have a replacement relay for only $9.49, and a replacement blower switch for $7.99.

The relay looks just like the GM one you linked to (thanks for the link, too!).

I think I'll pick up a replacement relay and try that first. As I mentioned, I didn't realize that there was a high speed blower relay, and just thought that I was dealing with a faulty switch. But the fact that only the high blower speed doesn't work, while the other speeds do, leads me to suspect the relay.

By the way, I was pleasantly surprised to find you out here in the "off season." Happy New Year!

DABA78 on Wed January 09, 2008 9:48 PM User is offline

Quote
Originally posted by: Chick
BTW, you might try unplugging the relay and cleaning the terminals, last one I had i had to keep wiggling the plug due to corrosion on the connection..Depends on how dirty they get...

Thanks for the suggestion...I'll make sure the connections are clean, first of all.

Chick on Wed January 09, 2008 9:50 PM User is offlineView users profile

The blower switch, like this one on the left also wear out when they are that old.. If not the relay, my money is on the tan blower switch... And yes, we're always here... Hope this helps..

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

DABA78 on Wed January 09, 2008 10:26 PM User is offline

O.K., thanks again.

I'll check back in and let you know how things turn out.

NickD on Thu January 10, 2008 8:22 AM User is offline

High speed blower circuit is usually on it's own 30 amp fuse, check that out as well.

DABA78 on Fri January 11, 2008 8:13 PM User is offline

Quote
Originally posted by: NickD
High speed blower circuit is usually on it's own 30 amp fuse, check that out as well.

Hello, NickD, good to see that you, along with Chick, are still around.

I did some more troubleshooting tonight, but am now more confused than ever.

First, I swapped the high-blower relay from my '77 Olds Delta 88 (same part), since I know the high blower speed works in the Delta 88. However, the high blower speed still doesn't work in the Cutlass, and I put the relay from the Cutlass into the Delta 88, and the high speed works in the Delta 88. So I think that I can rule out a bad relay.

Next, I put a voltmeter onto the high-speed terminal of the underhood relay connector, and when I put the blower speed switch to "High," I get 12 volts at the high-speed terminal, and when I turn the blower switch to a lower setting, I get no voltage at that high-speed terminal. So it seems that the blower control swich in the dashboard is OK, and I'm getting voltage up to the relay.

One thing I noticed tonight is what appears to be a metal-jacketed capacitor in the line going directly into the blower motor (it resembles the capacitors that used to be in the old style distributors that used points). My shop manual is actually for a '79 Cutlass. and the car in question in a '78. The manual shows no such capacitor. Any idea what that is? Of course, I would think that if it were faulty, no blower speeds would work...





Chick on Fri January 11, 2008 8:31 PM User is offlineView users profile

We used to call those condensers when in the distributors, (Surely served a different purpose) but I can't remember seeing one on blower motors... A epicure would help.. Is it in line, does any power go thru it? You might want to switch the blower motor resistor with the other car and try that. Could be both need to be working, and also make sure all the wires on the relay connection are working. If you can test power into it, find where it goes out.. May just hook into the resistor in some way I don't have any of those manuals around that I can think of, so either check all the wires, try changing the resistor (blower motor) and in the meantime someone with a better memory should be along....

There may also be a ground wire to the relay, make sure it's not broken.. Can't remember how many wires go to it, three or four I believe...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

Edited: Fri January 11, 2008 at 8:38 PM by Chick

DABA78 on Fri January 11, 2008 8:52 PM User is offline

Quote
Originally posted by: Chick
We used to call those condensers when in the distributors, (Surely served a different purpose) but I can't remember seeing one on blower motors... A epicure would help.. Is it in line, does any power go thru it? You might want to switch the blower motor resistor with the other car and try that. Could be both need to be working, and also make sure all the wires on the relay connection are working. If you can test power into it, find where it goes out.. May just hook into the resistor in some way I don't have any of those manuals around that I can think of, so either check all the wires, try changing the resistor (blower motor) and in the meantime someone with a better memory should be along....

Hi Chick,

I should have taken a picture, but it got dark on me pretty fast this evening. I'l try one tomorrow, using the camera that I got my wife for Christmas (but I've been hogging up...I don't think she's had a chance to take a single picture yet).

Yes, this capacitor-looking thing is directly in line in the wire which powers the blower motor (as far as I can determine, the only other wire to the blower motor goes to ground).

Good idea about swapping the resistor...I hadn't thought about that, but will give it a try tomorrow (supposed to be a high of around 48° here in southern Illinois tomorrow, so should be do-able).

Chick on Fri January 11, 2008 9:00 PM User is offlineView users profile

If it is in the 'hot" wire to the blower motor, obviously 12v is getting thru it, since the other speeds work? So I would be looking at the resistor or a wire in the blower relay. See if the manual you have shows a ground to the relay...If so, check that wire with an ohm meter to ground..You're getting close...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

DABA78 on Fri January 11, 2008 9:30 PM User is offline

I hadn't thought about the ground wire to the relay! I looked at the schematic, and have determined which contact on the relay connector it is. Tomorrow, I will use an ohmmeter as you suggested, and check for a good ground.

If the ground checks out, I'll try swapping the resistors between the Oldsmobiles to see if that helps.

Thanks for the additional leads...I'll keep you posted!

NickD on Fri January 11, 2008 10:02 PM User is offline

Nothing special about that capacitor or condenser or whatever you want to call it, just an RF filter to keep motor brush noise out of your AM radio. If you disconnect either of the blower motor leads, you should hear a click of the high speed relay when someone switches the blower to high with the ignition on and engine off. These relays have a dust cover that can be removed, and you can work the armature by hand, that should start the blower even with the ignition off. The contacts can be cleaned, like I said before, I don't toss my dirty dishes either and they are a lot cheaper than a new relay.

Chick on Fri January 11, 2008 10:19 PM User is offlineView users profile

Hey Nick, you da man when it comes to electrical, but just to point out that he tried both relays in the other car, and both worked, then neither worked in the problem car, 12v going to the relay, but obviously not coming out. I can't remember if those relays had ground wires, can you?? I have no diagrams at all home...just picking your brain...

-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

NickD on Fri January 11, 2008 11:19 PM User is offline

Relay coil is grounded, or should be, high side returns to the blower switch that applies 12V in the high position, I did read all the posts. Blower is working through the resistors, so the blower motor must work, so the question is, is this relay clicking? 12 V is also fed independently to the relay contacts, so don't confuse that with the coil voltage that comes from the switch, the motor feed comes through a 30 ampere fuse and is normally always hot, The resistor voltages are fed from the ignition switch, so two different paths to run the blower, they don't want the high speed running through those tiny ignition switch contacts. Hope this helps.

DABA78 on Sat January 12, 2008 7:58 PM User is offline

Thanks for the additional ideas, guys.

I spent some more time on it today, without success. As I said, I'm getting 12v to the relay connector when fan switch is in the "High" position. Also, as NickD suggested, I listened to the relay while someone turned the switch to the "High" setting with the ignition on, and definitely heard a "click" from the relay when this was done. But the blower still doesn't work on highest speed.

Another thing baffles me. As NickD mentioned, there is a terminal on the relay connector which steadily supplies voltage. I'm guessing that, when the relay coil is energized, a contact in the relay closes, allowing current to flow from the source to the blower motor.

The funny thing is, when I checked the voltage at the "always on" terminal, the reading is less than 12 volts (more like 11.4). Also, I pulled off one of the test leads from my multimeter, and stuck it between the "always on" terminal and the input power terminal of the blower motor, and nothing happened (curcuit should have been complete, since ground wire from blower motor to relay connector and wire from connector to engine ground wired together even when connector disconnected from relay, and I verified earlier that there is continuity from engine ground to ground terminal of connector).

This is baffling, but I'm not giving up!

Chick on Sat January 12, 2008 8:06 PM User is offlineView users profile

Did you try switching the resistor??


-------------------------
Chick
Email: Chick

---------------------------------------------

Freedoms just another word for nothing left to lose

DABA78 on Sat January 12, 2008 8:54 PM User is offline

Hi Chick --

Swapping the resistors is the one thing I didn't get around to this morning. I started to do that, and found that the steel spade contacts of the resistor block were rusted, and I had to remove the resistor from its mount, and then carefully pry it from its connector plug. I then cleaned all of the lugs on the resistor until shiny, and also pulled each brass contact out of the connector and cleaned all of them, too. I gave the spade lugs a thin coat of dielectric grease and put it all back together, but the high blower speed still didn't work.

At this point, I had to quit for the day and head to our favorite smorgasbord restaurant for lunch (a one hour, 15 minute drive from home), so I guess that I will try the resistor from the '77 Delta 88 tomorrow. I hope that it's not as rusty as the other one. I'll report back with the results!

NickD on Sat January 12, 2008 10:25 PM User is offline

What's very typical of these cars is unplated brass Packard Electric spade lug terminals that turn green, voltmeters typically have a high impedance of 10 megaohms that presents very little load to a circuit, but once the motor is loading the circuit, that voltage will drop to zero. These terminals can be removed from the housing with a small jewelers screwdriver and wire brushed clean. You also have to trace that source wire back to the source, can be a corroded fuse holder someplace also dropping all the voltage underload.

Did you locate that 30 amp fuse yet?

Your resistors are okay if all of your lower speeds work. What about running a jumper from the hot motor terminal directly to the positive post of the battery?

DABA78 on Sat January 12, 2008 11:25 PM User is offline

Hello, NickD --

I still haven't determined the location of that fuse. I wonder if it would be located somewhere besides the regular fuse block.

On the schematic diagram in the service manual, I can see the arrangement of all of the different wiring leading to the blower motor, relay, resistor, etc. The one part which I find a bit vague is the wire which supplies the constant current to the relay connector (the one where I picked up a reading of 11 volts, and which is connected to the blower motor when the relay is activated).

The schematic shows the wire going from the relay connector to a connector it shares with two wires on the thermostatic switch. Perhaps there is corrosion at this connector. I'm not sure where the thermostatic switch is physically located under the hood, but I can probably determine that my reading through the service manual, and find the connector being referred to.

After this connector, the conductor in question is shown terminating at another connector, although at that point, the diagram only says "PLUGS INTO ENGINE HARNESS" so if I can determine exactly what is meant by "ENGINE HARNESS" I might find corrosion at that connection.

I guess that the fuse feeding this conductor must be OK, since I am getting a reading at the relay connector?

Kaps on Sun January 13, 2008 12:06 AM User is offlineView users profile

Hi there.
Its been a long time, but if memory serves me correctly:
use a test light to check power thusly:

pull the resistor plug off
red, yellow blue are low. m1 and m2 speeds
orange is the feed from the hi blower relay
purple the feed to motor
if all 4 are OK, then its the resistor.

if no 12v @ the orange wire, its the fuse in line or relay
fuse in line is either in a harness along the pass side valve cover, or behind the engine along the firewall.
odds are very high the fuse in line is cooked, remove the whole assy and replace w/a new, 30A capacity 10 gauge wire fuseinline.

It is possible the resistor plug is cooked. Or the relay plug wires are cooked. To test this, rig fused jumper wire on battery, make another jumper from resistor output to blower, then test each input terminal indivudually by applying 12v. This will test the noise limiter/capacitor in the resistor if it has one. Use same bypass to test relay and relay wiring.

Old Pontiac tech service bulletin even suggested using two 20A fuse in lines in parallel for the feed to the high blower relay, giving 40a actual supply capacity. I prefered the 10 ga wire 30a fuse myself.

Let us know what you find.
Hope this helps,
Kaps


-------------------------
A. C. Doyle said "Eliminate all other factors, and the one which remains must be the truth."

Kaps on Sun January 13, 2008 12:12 AM User is offlineView users profile

After re reading your comments, i saw your thermostatic sw Q.
It is screwed into the the back of the passenger side head, and it is a pain to get at.
You will have to lie on the fender and stretch down behind the engine to get it.
I used double fender covers and no belt to prevent damage.
I think it will have either a 3/4 head, or a larger one.
You can always just put a jumper across the two terminals.
Kaps


-------------------------
A. C. Doyle said "Eliminate all other factors, and the one which remains must be the truth."

NickD on Sun January 13, 2008 6:48 AM User is offline

Never was hot on using a test lamp, maybe okay for checking out installing a trailer plug, but they do put a tad of a load on a circuit that pulls maybe 200 ma, still doesn't tell you the integrity of the circuit by judging the brightness of a light bulb. Why not, with the blower motor on in the high position, check the ground connector back to the negative post of the battery and the hot terminal back to the positive terminal of the battery with a voltmeter? The points that have the greatest voltage drops are where the problems are.

In testing out such key items like head lamp or fuel pump circuits, can see as much as a volt dropped going directly back to the battery posts, and narrowing down where that voltage is being dropped shows instantly where the problem is, can be a switch, a fuse holder, connector, or even a wire with a nick in it. Yeah, I made twenty foot long test leads for my voltmeter and use alligator clips a key points as my arms are not quite that long to use probes. If I get over a 100 millivolt drop in the head lamp circuits, I am looking for problems before they get serious and that's going from the terminal on the head lamp clear back to the respective post on the battery.

mhamilton on Sun January 13, 2008 10:39 AM User is offlineView users profile

I don't want to add confusion, but the thermostatic switch on this car is an interior temperature sensor behind the control head (the Comfortron had a coolant temp sensor, but not this one). On these A body cars, the low blower switch setting doesn't actually do anything. When the switch is in low, the blower is controlled only by the ambient temp sesnor, so that it runs on low when it's over 50 degrees. Part of the "flow through ventilation" system...

That capacitor is just a radio interference supressor. Will have no affect on motor operation. Most times it is part of the blower motor plug, but have seen them seperate.

This problem with no high speed is typical. As Chick said earlier, the relay and plug are suspect. I had the same exact problem where I replaced the switch, relay, blower, but still had no high speed. Turned out to be cruddy connections to the relay plug--fixed those and it's worked fine since.

The blower high speed is supplied with 12v through a fusible link (from the starter terminal). The three low speeds are through the control head, through the "ac/heater" 25A fuse.

Looking at the schematic, the orange wire will have 12v when the blower switch is on high. The blue wire will have less than 12v when on speeds 1, 2, or 3. Since your first three speeds work, you can ignore the blue wire. If you have 12v at the orange wire on "high," and 12v at the red wire, then either the relay or the plug connections are dirty.

This is the circuit we're looking at:



Edit: I scanned the FSM page for everyone to see. Four Season Air Conditioner Wiring

Edited: Sun January 13, 2008 at 1:48 PM by mhamilton

Back to Automotive Air Conditioning Forum

We've updated our forums!
Click here to visit the new forum

Archive Home

Copyright © 2016 Arizona Mobile Air Inc.