matchek

I put in a new hi-speed fan relay and connectors as they were fried and not in use for years. Lo and behond, the blower comes on high, but even if the car is off. When I try to adjust the fan speed to "Lo", the fan still runs on high whether car is off or on. Any ideas? I am just started digging.

3 things I can think of, my Dad messed with the wiring years ago - I remember he had installed a switch inside the car underneathe the A/C controls, but I did not notice it there , but I did not look too hard.

2) The manual says it runs on vacuum and I know the power door lock don't work anymore, so I don't know how well the vacuum is working on the switch.

3) Perhaps some grounding issue.

Attached is the blower diagram.

BILL DEMMER

another possibility-the contacts are welded together(stuck closed)
unplug the connector from the relay to check this. if the relay clicks when you unplug it or plug it in, the coil is being driven by a power source. if it doesn't click, the contacts are welded together. all of this assumes proper wiring connections exist.


bill

matchek

Hi Bill, thank you for your reply. For clarification, what could be welded together? Inside the relay? The relay connectors? It did the same thing with both the old and new relay if that helps.

Something that may offer a clue. I have the A/C Comfortron Thermostat. When the car is off, with the relay plugged in, the blower blows HI. When I adjust the thermostat to 65F, the A/C kicks on. When I put the fan speed on OFF or LO, the blower blows HI. When I put the fan speed on HI, DEFROST or DE-ICE, the fan blows low. The A/C blows ice cold.

joe_padavano

Bill has nailed it. The ONLY way for this to happen is for the high speed blower relay to go bad. The contacts inside the relay arc every time it is used. As these contacts get pitted, resistance increases, causing the contacts to weld together. This is what has happened. Replace the high speed blower relay.

matchek

Thanks Bill and Joe. The only problem is I just put in a new relay. It is doing this with the new relay and old relay. Unless the new relay is bad?

joe_padavano

OK, I missed that in your original post. The HVAC wiring uses the relay to bypass the speed control resistor and apply +12V directly to the blower motor. There are four wires on the relay plus ground through the case. One wire comes from the dash and powers the relay coil in the HIGH position. The relay contacts have one common wire that goes to the motor, one normally closed that is connected to the speed control resistor, and one normally open that is connected to +12V. When the dash control is in any position other than HIGH, the motor is supposed to be connected to the resistor through the normally closed contacts. When the dash switch is set to HIGH, the relay energizes and the motor is instead connected directly to +12V. If the relay is known to be good, then you've incorrectly connected the wires on the new connector.

If you pull the connector off the relay, does the motor turn off? If so, check for continuity between the motor contact on the relay and the +12V contact on the relay. If you get continuity, you have a bad relay. If not, you have bad wiring.

joe_padavano

This should help:

matchek

That diagram is awesome Joe.

When I disconnect plug, blow shuts off. There are two plugs going to relay.

3 pronged plug has
1) black coming from battery
2) brown going to blower
3) black going to blower

1 prong plug has:
1) light blow going to blower

How should I check continuity? I get 12 volts when I touch the black from battery plug with anything else.

joe_padavano

Look again. There is only ONE wire that goes to the blower motor. There is one wire from the battery, one wire from the switch on the dash, and one wire from the speed control resistor. You check continuity with either a powered test light or a VOM.

joe_padavano

By the way, take the old relay and remove the cover by bending the tabs. You can then see exactly which terminals on the relay correspond to the functions as shown on the diagram. One terminal will connect to the control coil - that one must be wired to the dash switch. One will be the common contact, which must be wired to the blower motor. The normally closed contact is wired to the speed control resistor, and the normally open contact is wired to the battery.

matchek

Joe, you got me thinking , would the power plug for the battery be the one that is all the way to right (the lone prong)? Right now I have it as part of one of the three.

For checking continuity , where do I put the positive and where the negative exactly? Connector plug? Relay? That is where I am missing.

matchek

By the way, looking at the diagram I do see your point as far as a bad relay or a relay wiring problem.
It is possible the plug wiring is off.

joe_padavano

Continuity doesn't care about polarity. All you are checking for is a copper path between the test probes. If you probe the relay terminals, you will get continuity from one terminal to ground. That is the control coil and must be wired to the dash switch. You should then get continuity between two of the remaining three terminals. Those are the normally closed terminals. Apply power to the control coil terminal (+12v) and you will hear the relay click. Now check continuity on the remaining three terminals again and you should see that two different terminals are connected. The one terminal that was common goes to the blower motor. The one that was connected to it without power goes to the resistor. The remaining one goes to the battery.

matchek

By the way, here is a pic of the relay cover off, situated the same way in the wiring diagram.

joe_padavano

The diagram is a schematic. It only shows connection, not physical orientation. The angle of your photo doesn't allow one to trace the actual connections inside the relay, so this may help. You'll need to trace the connections yourself to see which terminals correspond to which functions.

Toro X6

Folks, this is all good info, but Matchek's second post says its COMFORTON which uses a different blower motor control circuit than the one posted.
We'll need a COMFORTRON wiring diagram to properly diagnose this issue.

joe_padavano

Good catch. Sorry I missed that. Unfortunately, all bets are off. The 1968 comfortron uses a vacuum servo to automatically control blower motor speed. The relay only switches between low speed range and high speed range, but there are five speeds within each range. If the vacuum servo is not functioning properly, blower speed won't be correct. I suggest opening the Chassis Service Manual to the comfortron section (page 1D-16) and following the diagnostic procedures. Unfortunately, most of them require the Kent Moore comfortron test unit.

The first thing to do is to verify that all vacuum connections are correct. The power servo that controls motor speed is inside the passenger compartment, on top of the HVAC box.

matchek

PROBLEM SOLVED! Thank you gentlemen! Joe, by the way, where you did you get that wiring diagram? Not sure if I saw something like that in my manual.

It appears that the wiring of the relay plugs were incorrect. Looking at Joe's wiring diagram, and looking at the relay, it appeared that the power source was not wired in the correct location. But, Joe's wiring diagram is for a different year or maybe not Comfortron, the wiring colors did not match, so I guessed on the other two wires, and the other two wires could not tell if went to controller or resister as under black protector.

My first guess with other two wires yielded the blower off with power off, which is good, also LO fan worked witht controls, but no HI fan.

My second guess, interchanged the other two non-power plugs wiring, yielded perfect A/C fan controls!!!!!! HI, LO, and OFF when on OFF.

Thank you so much for your help with info and ideas! The A/C has not blown cold air in 15 years and now it is ice cold (knock on wood) and all the fans work properly.

My Dad said he never messed with the relay so he doesn't know why the wiring was off there, but anywho - all good now!