308QV Heater Blower(s)

Hi all, looking for someone to breakdown the heater blower system to help with diagnosing an issue. I did do a search and came up with some of the basics, blower motor for each side, relays in the kick well (maybe?) and of course the speed switch and light on instrument cluster. But I'm a bit confused on the relay(s).

So my issue is heater blower for drivers side works but only on the first speed. Light on dash stays on but when you move the switch to high no fan. But on low fan works. On Passenger side nothing on any speed.

If you could point me in the right direction to track this down it would be appreciated. Its getting chilly in the AM.

Thanks
jim

 

Can you please be more specific about year/version:

1983 US version 308QV
1984-85 US version 308QV
1982-86 Euro version 308QV

They are all probably similar, if not identical, for the heater blower system, but just want to look at only the correct schematic.

 

1984 US 308QV

jim

 

(Referring to an '85 Euro schematic) :

The heater light gets power from the switch, and then it goes to it's own ground. Power comes from the fusebox, and that's the same power line that feeds the switch output to the heater fans. Because the light comes on, as well as one blower, we know we have power at least to the switch.

For the moment, I'd focus more on the passenger fan not running, than the low/high not working on the drivers'.

I would start by checking the ground for the passenger side heater motor. Next, I'd apply 12V directly to the passenger fan, and see if it spins.

 

Agreed, could be bad ground of just a dead passenger fan. What does control the high and low speed? A relay? Location?

 

A combination of the switch, and the blower. The switch sends two 12V lines to the blower; the "hot" line is based on the switch position. A resistor at the blower's 12V terminal inputs determines fan speed.

The fans are wired, from the switch 12V (dual outs) -> passenger (terminals connected to psgr blower + out to driver) -> driver. Each fan has it's own ground.

 

Start troubleshooting at the fan end - chances are good that the mounting tabs on the fan housing are broken, and the fans are either dangling by the wires or the wires have pulled off and the fans are just sitting on the front spoiler undertray...

I had my front spoiler repainted in August - when the body shop removed the front spoiler, they found both fans dangling from the wires with the tabs broken. One fan had been grossly "repaired" with a heap of epoxy, and then it had broke again. With the spoiler removed, they supported the dangling fans and called me to come in and have a look:
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One of the wires had pulled out of the end on the fan, and had to be re-assembled. As always, whenever working on 3x8 wiring take the opportunity to clean every connection, sandpaper or emery paper and use contact enhancer.

On this fan they'd already applied some epoxy to the broken tabs:
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I made up new mounting brackets for the fan out of reasonably thick sheet aluminum, bolted/epoxied to the fan housing - these will not break again:
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Good pics and thanks for the direction to take. So it was simple. Just contacts needing cleaning. Pulled the wires off cleaned with some sandpaper and pushed back on both fans good to go.

Now I did check voltages and it just gets a lower than 12v for the slow speed. No resistors on the fans, so just curious how and where it getting the two different voltages for the fans?

thanks
jim

 

The symbol shown on your OM schematic shows that the resistor is located between the connector on the motor and the positive brush holder on the motor:
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but it also indicates that the voltage on the MB (brown-white) wire for high speed relative to the N ground wire should be +12V and the voltage on the MN (brown-black) wire for low speed relative to the N ground wire should also be +12V. Does your blower motor have three terminals and the three different wire colors shown (like in the schematic symbol) or only two? If only two, could be that someone replaced the blower motor (due to the broken ears issue), replaced it with something else, and moved the resistor upstream in the harness -- just a thought (if you do have a non-stock blower motor).

 

Ahhhh . . .So I have three wires. One Ground, then the two positive. the two go into a connector and then one comes out and goes under a plate. So I bet the resistor is under there and I just didnt have a good ground when I measured less than 12v

 

Pretty sure I said that?

 

I was expecting a resistor in plain sight, its hidden to fool the human (me)

 

Hi all,

Sorry to resurrect an old thread, but I have a similar issue. I replaced a missing heater fan only to find it has one positive and one negative connection but the wiring in my car has a single negative, but a double positive connector, which I assume is to connect to this link resistor. Looking at the other side, there is no resistor again and someone in the past has connected one feed to the fan so it turns on for switch position 1, but has no power for switch position 2.

Does anybody have a photo of this resistor, or can explain where it might be hidden? Or even a part number?

1979 Euro 308 GTS for reference.

 

107142: https://www.ferrariparts.co.uk/part/ferrari/107142
Item 30 here: https://www.ferrariparts.co.uk/diagram/ferrari/308-gtb-gts-carburetor/044-air-conditioning-system

 

Thanks Steve but I'm not sure these are right for the heater blower / fans, they appear to be for the AC system.

I'm looking at the fans located ahead of the front wheels, one either side.

 

My mistake. The documentation for you car only shows the single speed heater fan stuff (since this change was probably rolled in after the SPC and OM documentation was written for it). Couple questions:

1. What fan motor part number did you buy? The 308i-2V and 308QV documentation show that the resistor is built into the (3-terminal) fan motor itself so you may need to use a 308i-2V or 308QV fan motor -- but you should check the photos at MCP to see if physically the same or not.

2. You wrote "...but has no power for switch position 2". Does this mean you just have no where to connect the wire for position 2, or you have no +12V on the wire coming from switch position 2?

 

Thanks for your reply.

I bought the LHS Heater Blower Model
Original SPA L30804076 from Superformance

The new blower has 2 spade connections. I have a single wire connector (assumed earth) plus the twin spade connector which won't plug directly into the new blower as both spades are singles.

I believe from previous chat (page 1) that the twin connector will eventually end as a single connection with one wire passing directly (for higher speed) and the other through a resistor that will reduce the fan speed for the switch position 1.

Unfortunately the blower on the other side only has the one wire from the twin connector block.

As a side thought, is the resistor integral and the two spades for each speed rather than supply and earth?

 

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This is the new blower with the twin connector showing
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This is the twin connector on the opposite side that somebody has connected a single wire to one "port" which is connected to fan speed switch position 1.
Position 2 wire isn't connected, so the fan just turns off

 

Can't really say much more about it since your 155/78 OM schematic only shows the single-speed fan arrangement. You can always measure the voltage on that unused wire in the two pin connector relative to ground to see if it goes +12V when the switch is in position 2. The 1980 GTS/GTB SPC at Superformance shows two different F part number for each LH and RH heater fan -- I would guess those are singe-speed and two-speed (and don't know how those translate to the SPAL numbers). Since Superformance only shows one heater fan for each side (and we know that early carb 308 are single-speed and 308i-2V and 308QV are two-speed) maybe they don't offer what you need.

 

Thanks Steve. Both read 12v output, so it looks like a need to track down this in-line resistor.

 

Nice fix for a very common problem.