Jump to content
Home Page  | How to Join  | Official Merchandise  | Western Meet | Eastern Meet | Meet Photos | Technical Info  | Museum  | Parts Sources  | Officers

Recommended Posts

I have been trying to figure out what is going on with my Heater/Air Conditioning Blower.  The only setting the switch works on is "OFF" and "HIGH".  The Low, Medium 1 and Medium 2 blower speeds are inop.  Patsy and I drove up to Lutty's Chevy Parts today and I purchased a Blower Relay and the Blower Resistor assembly.  I replaced both of them today and neither of them fixed the problem.

I was looking at the wiring diagrams and there just isn't too many things that would cause this.  I would think i the blower switch on the interior dash were bad none of the speeds would work or maybe only one would fail.  I called Lutty's Chevy Parts and asked them to put one of the blower control switches on the trailer so I could get it when I go to Carlisle and they are going to do that so maybe we will have a parking lot repair seminar and replace it there.

Now, I have a question.  One of the things that confused me when looking at the wiring diagrams for 1970 Monte is there are two different Air Conditioning Systems.  I had been looking at the "Comfortron AC Wiring" and it shows two different relay's and I spent time trying to find the second relay before I turned the page and noticed the "4 Seasons Air Conditioning Wiring" diagram which only shows one relay.  My question on this is does anyone know what the Comfortron AC System was because the only one I knew about is the 4 Seasons AC.  I am wondering if the Comfortron system is one that the dealer would install at the dealership.

My next question is on relay's.  I found three relay's in the engine compartment.  One is located on the drivers side core support.  If I am not mistaken that is the Horn Relay, correct me if I am wrong.  

relay on core support driver side.jpg

 

The other two relay's are on the passenger side.  One is mounted onto the AC Evaporator Core plenum and is mounted, using two screws, and I suspect that is the Blower Motor Relay.  The other relay is mounted using rivets onto the plastic wire loom holder that runs across the firewall.  I am not sure what this relay is for so if anyone could help me on this I would appreciate it.  Shown in the picture below are these two relay's the one on the left has  black painted casing and the one on the right has a silver finish.  The black one I think is the blower relay.  Any comments?

relays on ac plenum and firewall.jpg

Thanks for your input.

I almost forgot... On the one mounted on the drivers side core support I have found a red wire that is not connected to anything.  If you look at this picture, you can see this red wire hanging down with the connector end of the wire sort of hiding behind the AC line.  If someone could look at their 70 Monte to see where this wire may belong.  I can feel a leg on that relay above it that does not have anything attached to it but I don't want to connect it to that relay without knowing for sure.

relay on core support driver side.jpg

rob

 

Share this post


Link to post
Share on other sites

If memory serves me correctly the other relay is for the tcs system for the transmission. Maybe someone can confirm. I would think your problem is the dash blower switch. I will try to confirm the relay....good luck

Share this post


Link to post
Share on other sites

Confirmed, page A5 UPC 12 in the assembly manual

Share this post


Link to post
Share on other sites

Thanks Charles.  I was thinking the other relay there was the TCS but wasn't positive.  Any ideas on the Comfortron AC System or the thinner red wire hanging up by the core support?

rob

 

Share this post


Link to post
Share on other sites

I believe the comfortron was a climate control system probably found on the capri and Cadillac's maybe some chevelle. I dont know if it was offered on monte carlos

Share this post


Link to post
Share on other sites

The only red wire shown in the 1970 wiring diagram at the horn relay is a 10 gauge that connects the the battery junction block on the radiator support. This same wire goes to the alternator and through a fusible link then to the firewall bulkhead connector.

About what gauge is this stray red wire?

Share this post


Link to post
Share on other sites

Thanks Paul.  I was not having any trouble decoding the wire colors, the trouble comes in where the colors don't match what is connected to relay and resistor block.  The other issue is not being able to see once they enter the relay or the resistor block what the connections are inside those. Having the pin-outs is only half of troubling in wiring.  I was a Senior Field Engineer and National Field Specialist working on blood analyzers for many years so I am used to troubleshooting electric/electronic items but usually what I was trouble shooting had reliable color designations or marked numbers and the all components were properly indicated.  

I hate having to shotgun troubleshoot an issue due to inadequate and inaccurate aids but that is what I am faced with.  

Regarding the loose wire, it is not anything as heave as a 10 gauge.  I did notice on the diagrams that the red wire attached to that relay came from the battery circuit and no other lighter gauge wire was shown, I am just not sure what it is from.

rob

Share this post


Link to post
Share on other sites

Here's something I never understood about these cars (and probably all GM A-bodies of the time). All cars were built with a non-AC dash harness that had a blower resister under the dash. If a car coming down the line called for AC, it received an add-on harness. The under dash blower resistor was unplugged and set aside.

Share this post


Link to post
Share on other sites

I ran my hood light to the relay like they used to do, maybe someone ran some accessory from he block years ago and used the wrong colored wire????

Share this post


Link to post
Share on other sites

I know on the 71's that there is a resistor also mounted on the other side of the heater box under the POA valve (it shows as "resistor" in Pauls wiring diagram). My understanding was that this is the one that controlled the low blower. I know the low blower and high blower have separate relays. It's been a long time since I've worked on these AC's so I'm a little weak in this area. 

Unknown what that red wire is without a full under hood wiring diagram (I'm at work...lol). But it does not appear to be part of the AC system.

Share this post


Link to post
Share on other sites
4 hours ago, Monteman1971 said:

I know on the 71's that there is a resistor also mounted on the other side of the heater box under the POA valve (it shows as "resistor" in Pauls wiring diagram). My understanding was that this is the one that controlled the low blower. I know the low blower and high blower have separate relays. It's been a long time since I've worked on these AC's so I'm a little weak in this area. 

Unknown what that red wire is without a full under hood wiring diagram (I'm at work...lol). But it does not appear to be part of the AC system.

Steve, thanks for the reply.  I did try a new resistor assembly but it didn't help.

rob

Share this post


Link to post
Share on other sites

The dash switch sends power to the various resistor terminals in the AC box under the hood as needed for the speed setting except for the high speed, which uses the relay.  There's no relay for the lower speeds.

A non-AC car has no relay at all, all speeds go through the dash switch and resistor set, which is under the dash.

The reason AC cars had a relay for the high speed and non-AC cars high speed came from the switch is because AC cars got a more powerful blower motor.

Share this post


Link to post
Share on other sites

Rob, in every dash switch setting (except for off and high) you should see 12v at at least one terminal in the resistor plug. IOW, low, medium low and medium high should send 12v to the light blue, yellow or green wires. If you do NOT have this voltage, there's a problem in the dash wiring. One wire from the resistor pack plug, dark blue, splices to the purple wire going to the blower motor. I think the splice is actually in the harness under the wrap.

AC resistor.jpg

Share this post


Link to post
Share on other sites

Paul, Thanks Again,  I agree with everything based upon the drawing.  It appears that since the blower works on High the blower switch is providing power to the relay which is sitting with 12 volts which is coming from the horn relay leg and goes to the orange wire with an inline fuse.  So when the switch is moved to the High position it energizes the relay and passes that 12 volts through the relay contact and out of the relay on the purple wire to the blower motor.

It would stand to reason that since it works on high that it should work on the Low, Med 1 and Med 2 speeds too since the 12 volts that went to the relay when the switch is on high should be the same 12 volts that would go to the Air Conditioning plenum  resister pack through the light blue, light green and yellow wires.   If it were the blower switch I would expect maybe one of the speeds to work but not all of them except the High position.  

Once I get the new switch I will I will try it and see if it helps.

Paul, thank you for all of your input, it is great.  Now I just don't know why wire colors on my car just don't match the schematics.

rob

Share this post


Link to post
Share on other sites

I believe the dash switch has two plugs in it. Two resistor feed wires go to one plug, one resistor feed wire goes to the other plug. If either plug pulled off the switch terminals, you'd have a different problem.

I'd check the dark blue where it meets up with the purple motor feed wire.

Share this post


Link to post
Share on other sites

Thanks again Paul, I will check things out as much as I can on Sunday at a car show my grandson's scout troop is hosting or before I go to my Carlisle Mini-Meet..... or maybe we will host a repair seminar in the hotel parking lot.

rob

Share this post


Link to post
Share on other sites

I think the comfortron system had a thermastat on the dash that you could set a particular degree temp and it was suppose to stay there. I had a 72 caprice with this setup did not work very good.  you had to have windows up or the ambient temp would cause the system to malfunction

Share this post


Link to post
Share on other sites

I found this posted by one of the founders over at Chevelles:

The underdash a/c units were simply called Comfort Car Air Conditioning and they were for dealer installation. They were recirculating air units that operated independently from the heater/defroster.

The factory-installed in-dash a/c in Chevelles and most other car lines was referred to as Four Season Air Conditioning. It worked in conjunction with the heater/defroster and could recirculate inside air, blend it with outside air or bring in all outside air. It also dehumidified the air as it cooled or conditioned it.

The Comfortron Air Conditioning was a modified version of the Four Season a/c. It incorporated electro-mechanical and vacuum controls to automatically maintain a selected temperature. There was a temperature sensor in the interior of the car. The Comfortron a/c was only offered in full-size Chevies (starting in 1967), not Chevelles or other models.

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×