84 911 Engine Compartment Blower Fan SituationT

[Jtt84911]

Hi Guys,

Engine mounted blower fan no longer comes on like it once did. I've already removed the blower unit, ran 12v to it and confirmed it's fine

From what I've read.. it looks like the problem is either the "expensive silver box" (blower relay in engine panel) is no good or the rotary temp selector switch (ie the numerical blue white red 1-9 temp settings) is not working properly?

I am somewhat confused about the many sequential functions associated with the rotary switch.. so here's my situation and question.

1-What should I check next?
2-What do I need to do to get the blower working properly again??

Thanks!
JT

PS- the PP 911 Forum is AMAZING!! Can't believe the interest levels and great info shared between all of us 911 people!!

[mpetry]

Take the blower motor apart, IRAN (clean / lube all contact surfaces, inspect repair as necessary) reassemble and test.

and report back !

[Bob Kontak]

Here is a diagram for the 84.

Basic electrical trouble shooting looking for continuity and voltage.

First step, see if there is voltage at the hot wire to the fan when things are turned on and see if the other side grounds properly to the chassis.

[Bob Kontak]

Send me a PM if you want me to e-mail these pics to you. They will have better clarity.

Just click on my name in the upper left of this post to see options.

[Jtt84911]

Hi Mark. Thanks for the response but as I said in my post the blower motor is fine the problem is elsewhere.
JT

[Jtt84911]

Hi Bob,
Will remove relay checkand clean contacts,chech fuses and check voltage at blower plug. From what I recall when temp selctor is at 9 all 3 blowers (2 front + rear) are on 100% . Will then check voltage at plug. Theres only 2 contacts so assume 1 is power other ground.
JT

[Jtt84911]

Well...checked relay plug - no breaks in wire solder,and fuses OK..... turned temp selector to 9 and started motor...... unfortunately NO POWER at blower motor plug. Though I remembered reading that blowere needed to be mounted on the three mounting bolts in order to function so mounted and nothing..

I guess it's probably the relay?? Other than plugging in a replcement. ... does anyone know if there's any way to check if the relay is bad? What would be obviously wrong when the case is removed? Can they be repaired? Doesn't appear they can be - from what I've read.

[Monza_dh]

Why woul the relay be so expensive? You should find one on a car that is parting or DC Auto etc for not too much. I bought one for $25 when I had issues with mine a few yrars ago,

[pete3799]

Have you checked the fuse in the engine compartment?
Think it's the top one.

[Targa Me]

Here's what you need to do.
Buy 2, 5-pin relays and replace the guts of your eng compartment relay.




Hope this helps.

[jwakil]

My advice would be just get rid of the whole blower and associated piping. It is a useless thing, and will clear up a lot of space in your engine bay.

[Jtt84911]

Hi Targa Me and Jwakil,
Read a number of things about checking the plug contacts for this relay to see if the various things on the other end are functioning and there power..... but don't believe I've seen your idea Targa Me about building a new new relay in the original housing/base! Interesting cocept.

I'm guessing you eliminated the engine blower? Should be a lot less $$ than new replacement.

QUESTION: for both of you:.... if you eliminate the rear blower do the two front footwell blowers still work? I thinkj they will not?? Jwakil- I live in NJ and athough I dont drive the car a lot in the winter.. I do drive it (because its good to keep it running and I love driving it) so I need heat and need the duct work.
JT

[jwakil]

Originally Posted by Jtt84911

Hi Targa Me and Jwakil,
Read a number of things about checking the plug contacts for this relay to see if the various things on the other end are functioning and there power..... but don't believe I've seen your idea Targa Me about building a new new relay in the original housing/base! Interesting cocept.

I'm guessing you eliminated the engine blower? Should be a lot less $$ than new replacement.

QUESTION: for both of you:.... if you eliminate the rear blower do the two front footwell blowers still work? I thinkj they will not?? Jwakil- I live in NJ and athough I dont drive the car a lot in the winter.. I do drive it (because its good to keep it running and I love driving it) so I need heat and need the duct work.
JT

You will still get decent heat. You just need to do a heater back date, which requires two ducts that allow you to connect the heat exchanger pipes directly to the engine fan shroud.
Porsche 911 & Carrera Heating & Ventilation - Page 2

[Jtt84911]

Since I wasn't 100% sure if both foot well flowers were still working, I removed carpeted panels and ran direct 12v to each and they ran perfect..... so now I have confirmed all 3 blower motors are fine...so issue is either the engine blower relay or wiring. This weekend I will check circuit readings at the relay plug and confirm current is reaching relay.
J T T.

[donagain1]

Not exactly certain about the autoheat controls since my '85 has the twin levers down by the console, and on the manual system one or another of those must be raised in order for the relay in the fan control module to operate the rear blower. Current for the footwell blowers flows through the winding of the relay that switches on to provide power to the relay in the luggage compartment that switches on the footwell blowers. Hence, if rear blow no go, neither will the footwells.

If you've got a voltmeter with test prods and care to check conditions at the fan control module socket with the module unplugged, here's some pertinent pin assignments. You can see the pin position numbers embossed on the socket if you've got a flashlight, good eyes, and patience.

Pin#2 goes to ground;

Pin#12 brings in 12V from Fuse#8 in luggage compartment via ignition key in "on" position (makes stuff in the module work);

12V (Hot from Fuse#1 on rear panel) should be present on pin #3 (This feeds through contacts on 2nd relay in module to come out on pin #4 to get to rotary switch in console and power the footwell blower relay.

12V (Hot from Fuse#2 on rear panel) should be present on both pins 7 & 8; (the source for the rear blower)

Pin #5 & 6 both go to the hot side of the rear blower motor (other side of blower goes to ground).

If you've got 12V on pin 7 and/or 8, you can jumper one of them across to pin 5 and/or 6 and the rear blower should fire up for you.

Applying 12V to pin #4 provides the operate path for the luggage compartment air blower relay, which gets its ground when the rotary switch is in the high speed position.

From what I can tell, the inside lever being raised should provide the contact closure across pins 9 & 11, and if you ain't got that, I'm thinking that none of it'll work.

Blown fuses or toasted relays are the best bets for a sudden failure of something that had been working before.

Don

[Targa Me]

Jtt, the schematic and photo I posted is not my original idea, someone from here posted it sometime ago.
The setup I posted will allow you to use the footwell blowers as described in the schmatic.
I have not deleted the rear engine blower. Here in So Cal its a must to help keep the engine cool.

[Jtt84911]

Thanks Guys. Will be away on business trip for few days but this weekend I will check for power and jump as Don suggested. I'm thinking the rear blower will fire up at that point. I also think I actually may have fried this rear rely myself.....because a while back I remember working in the engine area with the fuse cover off and accidentally bridging the fuses with the handle of a ratchet or wrench!!!

Sparks scared the hell out of me! Something you do Once! Wondered if it caused a problem.......but I think we all know the answer.

J T T

[Monza_dh]

I have an '88 and got rid of my rear blower a few years ago. Unless you drive in the rain etc you can live without it. I also modified the relay so my footwell blowers will work once the rear blower is removed. Makes for a much cleaner engine bay.

read this:
Why you should backdate your heat on a 3.2

[Jtt84911]

Donagain1

YOU WERE 100% ON THE MONEY WITH YOUR ADVICE AND DIRECTIONS!

Had 12v at the pin locations (#3#7#8) and when I jumped to #5 the bower kicked in..... and when I jumped to #4 and turned rotary switch to (9) both FW blowers came on as well !!

Good News: Have confirmed the rear blower relay (911.618.153.00) is shot and everything else is in order and operates as it should.

Bad News: Have conformed the relay's shot!

Just came in from garage and not 100% sure what I'm going to do. Will ponder this over a few beers and cigar. Although Targa Me's dual relay direction is interesting.. I would want the diode added... for engine cooling option.. so I'm leaning towards buying another OEM relay. (911.618.153.00)

Initial web price searches for New are pretty crazy (have seen over $300) so I'll be checking the used market right away.

THANKS!
JT

[Jtt84911]

Hi to anyone still following my posts! Have UPDATE and question,

UPDATE
Well... based on everything that happenned in the posts below...decied I wanted to replace the blower relay ... but wasn't going to spend almost $400 for a new one.. so...almost 2 weeks ago (Sept 23rd) I ordered a used blower relay from DC Automotive in NC....along with a few small parts (several clamps, auto heater arm ball socket)

The order left NC on 9/26 FEDEX ground. Afew days later.. nothing. Phoned DC and while on the phone they checked tracking and told me my package was in CALIFORNIA!!!! I live in NJ!!!I said you have to be ****** joking----- they were not. I phoned FEDEX.... and since it was Ground not Air... it had to come back 3,000 miles ground. DIDN"T GET THE RELAY TILL A FEW HOURS AGO!!!

GOOD NEWS... everything works perfectly.. engine blower works like it shoud and (2) footwell blowers work great (ie. all (3) air speeds) and although it's cool tonite (55-60 degrees) with [B] the roof off (Targa) ... and heat on 8.... the car is like an oven!! Touch the two floor vents with bare feet or legs...you're in trouble!! [/B]

QUESTION
Rear blower is realatively near engine but the very hot air in the heat exchangers is being blown away from the blower motor... so why would the rear blower motor be SO HOT!!!

I felt if for the hell of it before shutting down car and it was very hot... like you could not keep you hand on for 2 seconds hot!!!

IS THIS COOL???? (pun intended) Can't belive an electric motor should get that hot... but it is in the engine bay a few feet from the motor.

JT