[gido]

The heater fan switch is acting up. Sometimes comes on as it should; sometimes takes up to 15 minutes or more of engine operating before it works; sometimes comes on and off intermitently. Sometimes it will function after I release the parking brake. Occassionaly it will run on after I turn off the ignition. All this seems to happen when it's cold outside - say 5 degrees above freezing or colder. My research tells me that it's probably the heater fan control relay - the one that's mounted up behind the body control module above the driver's left foot.

I've gone to the boneyard to see how difficult it is to replace. None of the vans there have the relay as described in the info that I've downloaded from the web. All I can find is something that looks like a small bell transformer connected by two wires. Is this what I'm looking for? The web description talks about a black relay box with four wires - albeit in the same location as the 'transformer' on my vehicle.

 

[Bob Lincoln]

Do you know if there is actually a relay?
Do you have automatic climate control? It would cause most of these symptoms when it is acting normally.

 

[gido]

Don't have auto climate control. I'm just following the postings of HeadlessHorseman in this forum about this problem. Couldn't see a relay when I was in three different vans at the boneyard.

 

[ImperialCrown]

It probably isn't a relay problem, even if there is one. Get a good service manual and follow the troubleshooting for 'blower motor inoperative'. You want to perform the tests while the fan isn't working. If the fan is working then it will pass all the tests.
There was a recall on '96 NS for blower motor resistor connectors that corroded and burned up from high resistance at the terminals. It is located at the right firewall behind the strut tower. Sometimes by wiggling the wires, the blower will kick on if it is bad.

 

[John Wood]

This is a 96 Gen III mini, and it does have a HVAC system relay. For the 96 only mini-vans, the relay is located on the inside of the vehicle, up under the lower left dash, behind the BCM. It is clipped on a bracket and is very difficult to get to. It takes a lot of disassembly to get at it. It is almost as if the relay was installed as an afterthought or perhaps it was omitted from the original design plans.

Your symptoms are exactly the same as I had and it was a bad relay. Just hitting a bump would sometimes turn it on and occasionally the contacts would stick, causing the fan to stay on after you removed the key and walked away from the vehicle. Releasing the hand brake will sometimes provide enough vibration or "thump" to cause the relay contacts to unstick.

Note that you will not be able to buy the exact relay with the bracket clip. The dealer will probably sell you a square standard relay which will plug directly into the wiring harness connector. It will work fine but just not clip up to the bracket on the firewall. Electrical tape will be used instead to hold it in-place. Ironically, the exact replacement relay with the bracket is the same as my starter relay on my 1991 Dodge Spirit.

The only place you will get the exact description and a diagram of this setup is from a 1996 NS Factory Service Manual. For all the remaining Gen III model years, the blower relay was installed in the Power Distribution Center, as it should have been in 1996.

I actually removed my BCM to get a full view and access of the relay. If you know what you are looking for and can work blindly (or even with a mirror) you could access the relay with a lot of bending, croaching, and contorting.

There are old posts on Allpar on this subject, but it hasn't come up in a long time. It is very unlikely that the problem is your heater control panel switch, based on several experiences posted on this board over the years.

 

[Bob Lincoln]

Contacts sticking (welding) shut are usually due to excessive capacitance across the load. As the relay starts to open, the capacitance discharges and arcs across the contacts, causing them to weld/stick. I've seen this issue at work. Not sure off-hand what can be done to reduce the capacitance of the fan load, but doing so will reduce the chance of this happening again.

 

[John Wood]

I had a lot of relay problems on this van which I find unusual. Over the years I had to replace wiper relays, the Anti-lock brake pump relay, the fuel pump relay, and the blower relay. There was a time when I was about 80 miles from home and had to get a jump due to the vehicle battery experiencing total failure. I drove home on mostly alternator power which is not clean DC power. I suspect my relay problems were caused by that situation.

Since I replaced the battery and the bad relays (which failed at random intervals at a later time), I have had no more problems. The new blower relay has been in the van going on 5+ years with no problems. I'm going to speculate that the problem, in my case, was caused by dirty DC power by not having the benefit of the battery to filter the crappy alternator voltage.

 

[gido]

Thanks John Wood. Your advice matches what I've heard from some other sources. Is it possible to reach up behind the BCM and detach the wires while leaving the old relay in place?

And does anyone know what the other 'bell transformer' item is that's up behind the right side of the BCM?

 

[John Wood]

Thanks John Wood. Your advice matches what I've heard from some other sources. Is it possible to reach up behind the BCM and detach the wires while leaving the old relay in place?

And does anyone know what the other 'bell transformer' item is that's up behind the right side of the BCM?

It has been a few years since I did this job so this is a description the best I can remember. I had to take the lower left dash panel off and that means removing the brake release handle. The relay is really on a stationary clip, so you should be able to slide the relay/case combination straight down and off the clip. The assembly will then be teathered by a wiring harness. In order to get the relay out of the connector, you have to gently pull back the clips on both sides simultaneously and pull the relay/case out of the harness connector. This is why it is so hard to do blindly. I seem to remember sticking a screw driver in behind one of the clips, leaving the clip forced outward while I used one hand to release the other clip and the other hand to pull the relay out of the harness connector. If you know what one of those fender mounted relays look like on an EEK car, you will be looking at a similar setup with the only difference being that you don't have a push pin retainer holding it into the fender. Those relays all have a larger case with a slot in the back.

Frankly, removing the BCM was not that hard. I think there were 2 or 3 long hex head screws that had to be unscrewed and then the edge connector pulls out from the junction block assembly. It just seemed like a lot of work at the time, just to replace a simple relay.

 

[gido]

Thanks John. And it turns out that the transformer that I was describing is to power the Infinity speaker system.