I have a 1995 Ford Motorhome. The Blower fan will not operate. I have tested the control switches, the blower motor , the relays and the resistor. I have replaced the relay with a known good one. They all seem to be ok. When I jumper terminal 30 and terminal 87 on the relay socket, everything works, the blower speed, the damper positions, everything. When I replace the relay into the socket, nothing works. I have 13.2 volts on terminals 30, 85 AND 86. I do not have voltage on 87 or 87A. Is this correct?

 

The relay in front of the radiator in side the relay/fuse box should click when you turn on the key.
You should not have power on both 85 and 86.
One of them goes to the ignition switch and the other goes to ground.










G100 is on the RH side of steering column, rear of dash panel (A1 in diagram below):



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Was the relay installed (pluged in) when you checked the voltages or did you pull the relay and probe the connections where the relay plugs into?

Jim

 

The relay was plugged in. I also just bought a new relay. It still doesn't change anything.

My 35' Pace Arrow is built on a 95 F53 460 Chassis. It does not appear to be the Evans HVAC system. I have purchased three separate ford wiring diagrams. They all show completely different color codes. My system 12v main power to the hvac system is Blue wire w/ red stripe. It goes directly to the Blower relay pin #87. The blower motor has one blue wire and one blue w/white stripe. All of the wiring diagrams show brown/orange and orange/black wires. I am getting very frustrated.

 

"You should not have power on both 85 and 86.
One of them goes to the ignition switch and the other goes to ground.

Sounds like you have lost the ground to the relay."

I agree with this.
Pull the relay and see which has power, 85 or 86.
The one that does not have power is the ground, add a ground and see if it works.

 

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I think that I'm making progress. First, with the relay removed and power off, I get the following readings:

Pin 30 - Grounded 3.2 ohms
Pin 85 - Nothing
Pin 86 - Grounded 3.2 ohms
Pin 87 - Nothing
Pin 87A Grounded

When I turn on the Power:

Pin 30 - Grounded 0.6 ohms
Pin 85 - Nothing
Pin 86 - 12 volts
Pin 87 - 12 volts
Pin 87A Grounded

I then replaced the relay and jumpered Pin 85 to ground:

Everything worked, but with the following issues:

Blower fan switch - High Actual blower speed high
Blower fan switch - Medium High Actual blower speed medium high
Blower fan switch - Medium Low Actual blower speed medium low
Blower fan switch - Low Actual blower speed low
Blower fan switch - Off Actual blower speed low

I then checked the wire to relay pin 85. The wire is red/black. The only other terminal in the system was on the blower fan switch. When I tested the wire, there was on continuity. When I jumper the wire from the switch to the relay, everything works fine.

Thanks to everyone for your help.

 

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"Pin #30 is the power that passes through the relay to make the fan motor run.
If it is at ground with the power off and on then the yellow #37 wire is shorted to ground and the supply fuse "P" is now open (bad)."

I just think it is wired backwards. Power going in on 87 and out to the blower motor on pin 30

 

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OK lets start over.
I see the problem with us helping you.
I have been talking about the FORD relay part in the fuse/relay box in front of the radiator.
You are talking about another relay installed by Denso the maker of your dash air.
The wiring diagram for this system is very large and I can not post it here.
Your wiring colors are right.

I need to know what type system you have:
The Push Button Type
The Rotary Dial Type
The Rotary Dial Type with Supplemental Defrost
The Electronic Dial Type

That way I will know the right diagram to look at.
I can send you the diagram also if you email me at the email below in my post.

 

Here is a cut down part of the Denso Blower circuit:


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This is all normal.

Pin 87 is a ground pin and should not be 12 volts.

This would be the way it should work with Pin 85 grounded.

Sounds like the red/black wire is open from the relay to the switch is open (bad).

 

The red/black wire had no continuity through the large connector. I wired a jumper around the connector and everything works exactly as it should.

Thanks for your help.