Help with a friend's car please folks

[Jonathan]

I am trying to help a friend nearby get a few remaining things resolved on his car. I'd love some help from the group figuring it out.

1) Cooling fans:

They don't come on. Not when the otterstat is jumpered nor when you turn the A/C on to MAX.
It has what I understand to be the original style to the "fan fail" relay socket, meaning, in that corner socket is a red/orange box/relay and I am not sure what might be broken inside it. What goes on in there, how do you fix it, or what do you put in it's place as an upgrade?
Cooling fans look okay from peering udnerneath. Electrical quick connects appear fine and snug.
**possibly related** The temp gauge in the dash immediately pegs to straight vertical once you turn the car on. It did it each time we started the car or turned to accessories, and it happened regardless of whether the otterstat was jumpered or normally plugged in. Is there any type of feedback from the gauge back to the diodes or something that would be tricking the car into not turning the fans on? I am guessing not, but it's unusual to see this needle pointed straight up. And it's a brand new gauge and did it from day one apparently.

Volts when idling was just under 13. That's a bit lower than my car, but not sure if too low. It idled nice, but did stall when I tried it in MAX A/C for the fan test.

2) Black smoke from exhaust. Not at all while idling, only when you give it some throttle. And it "pops" a bit like you might hear when "snapping the gas" on a turbo S4 or something. Is this a simple case of the engine running too rich? Would a dwell meter and an adjustment save the day? Anything more to this? Can it be related to the catalytic converter doing something out of sorts?

Those are the only main things to tackle for now. We have an infared temp gun and when pointed at the engine, it is not overheating, but we didn't leave it running for so long that the cooling fans not coming on would have affected it.

[DMCMW Dave]

Pointing straight up = disconnected gauge sender. Could be at the gauge, bulkhead, or in the cluster. .

Feed 12 V to the connections on either side of the blue fan socket. The fans should come on one at a time as you feed either side. If so everything is good from the socket to the fans. Problem will be the wiring, relay, diodes.

Mixture is way off. Sorry - could be lots of things, from fuel distributor to a lambda (frequency valve system) that is dead. Get the fans working first, then you can troubleshoot. Do you hear the frequency valve buzzing?

[Jonathan]

Pointing straight up = disconnected gauge sender. Could be at the gauge, bulkhead, or in the cluster. .

Feed 12 V to the connections on either side of the blue fan socket. The fans should come on one at a time as you feed either side. If so everything is good from the socket to the fans. Problem will be the wiring, relay, diodes.

Mixture is way off. Sorry - could be lots of things, from fuel distributor to a lambda (frequency valve system) that is dead. Get the fans working first, then you can troubleshoot. Do you hear the frequency valve buzzing?

Pointing straight up... I know what you mean, sort of like we always see with the fuel gauges. The odd thing is, it goes back down to the normal low resting point when the car is off. Does that still point (hehe, no pun intended!) to the same problem? I bet it does and it just has something to do with the gauge only getting 12 V once you turn the key.

Ok, we can pull the orange relay cube out of there and try the straight 12 V to each side. That'll be a good test. What goes in there long term? (I know my car has had the relay/fuse upgrade kit installed, but I can't remember if the fan fail socket was one of them in the kit).

We'll try the fans and gauge first. Frequency valve buzzing... I have to admit something here... I don't even know what this buzzing sounds like on my own car. LOL Everyone talks about it, and I've just nodded my head agreeing. I'll have a listen for it when I'm back working on the car (anyone got a YouTube vid where you can make out the buzzing?)

Thanks Dave.

[DMCMW Dave]

Pointing straight up... I know what you mean, sort of like we always see with the fuel gauges. The odd thing is, it goes back down to the normal low resting point when the car is off. Does that still point (hehe, no pun intended!) to the same problem? I bet it does and it just has something to do with the gauge only getting 12 V once you turn the key.

Ok, we can pull the orange relay cube out of there and try the straight 12 V to each side. That'll be a good test. What goes in there long term? (I know my car has had the relay/fuse upgrade kit installed, but I can't remember if the fan fail socket was one of them in the kit).

We'll try the fans and gauge first. Frequency valve buzzing... I have to admit something here... I don't even know what this buzzing sounds like on my own car. LOL Everyone talks about it, and I've just nodded my head agreeing. I'll have a listen for it when I'm back working on the car (anyone got a YouTube vid where you can make out the buzzing?)

Thanks Dave.

Yes - when the power is off it goes to zero. With power on and an open circuit it will point up. Gauge is probably good.

WHAT orange module? Should be blue (OEM) or a the two wires which may or may not have fuse jumpers.

Turn on the key and "bump" the starter without starting the car. You should hear the fuel pump run for a few seconds, AND the frequency valve buzz for the same amount of time. Put a finger on the frequency valve and you will feel it. If not, you have other issues to solve.

[DMC5180]

Don't mistake ISM hum/buzz with FV buzz. Put your finger on it as Dave mentioned.

[Jonathan]

WHAT orange module? Should be blue (OEM) or a the two wires which may or may not have fuse jumpers.

My bad. I was looking at the wrong relay. It is in there and is blue and says Pektron on it. Should I be fiddling with it?

If I pull it out, I am guessing this is where I can put the straight 12 V on each side?

[Cory W]

That blue module should be replaced with a 3-prong fused jumper. I suspect that it finally gave up the ghost, and that's why the fans didn't turn on. I'm betting that is the culprit right there.

It was included in the relay upgrade kit, and you can make one yourself using simple parts from your local CanTire.

This is what it looks like. (http://store.delorean.com/p-7225-wire-link-fused.aspx) It uses 20 amp fuses.

It goes in the two outer side plugs, plus the bottom most plug (center, joined blade).

If that doesn't work, then you can dig deeper and see what else may be causing the problem.

[lazabby]

You may be having an RPM drop when you turn on the AC causing the car to stall. I'm having a similar issue with ROM dropping more than normal. Post the solution when you find it.

[Jonathan]

Okay, so we made some progress on the car tonight. Likely could have made a bit more, but I'll blame that on the beer and the women ;) hehe

So, like I said, the original blue relay is in position. Good call on it possibly being the problem, Cory. What I did find was that once I pulled it out, and put 12 V directly from the positive side of the battery to the right and then left sockets, the fans do come on (with the key turned to accessories).

So that part is good. I will work on making one of the in line fuse arrangements as mentioned. I have this on my car back home, so I think I have a pretty good handle on what it would take to make one.

A couple other observations:

The car fires right up, but in my opinion is idling a bit low. I would say it is closer to 600 RPM than it is to 775 RPM. The car feels like it is thinking about stalling, but for the short period of time we ran it, it did not. I did not put the HVAC selector to MAX AC again, instead it was OFF. The owner also mentioned he thought the new DVD screen radio deck might be using a fair bit of the power.

Along those lines, I noticed the volts are a little UNDER 13 V instead of being a little OVER 13 V. Not sure where this ranks in terms of being normal, but my car (the only one I am really familiar with) is a little bit over 13 V when running. It might be related to the battery not being fully charged after getting turned on and off again many times, and not having the car out for a real long drive. I think the general train of thought is that if you don't get it up to speed, the alternator doesn't charge the battery very well. We may take it out and charge it on the workbench before the next session.

I don't know what might be leading to the weak idling issue, but another helper thought it could be a vacuum leak or something contributing to it.

On the temperature gauge, everything behind the cluster looks okay. Mind you it is so hard to get your neck around to see stuff. The black connector, which is mentioned in the circuit diagram for the instrument cluster connectors, looks okay, but my fingers couldn't get very close to it. Nothing else looks out of place, but I didn't follow where the wiring went as it got lost behind some trim.

I double checked how snug the connection was on #29 of the white connector in the bulkhead and it looks okay. I did realize that the needle DOES NOT go back to zero when the car is off, instead it is pegged all the time. And also of note, is that it is not pegged straight up like we see our fuel gauges do, no, this needle is past straight up, pointing closer to 1 o'clock. The owner mentioned he has before pushed the needle with a wire through the trip reset shaft hole and got it back down, which stays down once the car is running, but as soon as you shut the car off and turn it back on, it shoots back up to 1 o'clock. Anyone make sense of that? It sounds more like a bad gauge now than it did the other day when we thought there was a wire loose.

That's it for now... thanks for the help :)

[Jonathan]

Another chance to work a bit on the car tonight.

I put my 20 Amp inline fuse wiring set-up in the fan fail socket and didn't get the results I was hoping for. Fans did not come on whether I had the A/C to MAX (with the key turned to accessories/ON), nor did they come on when I jumpered the otterstat connectors. The earlier day the fans did come on when I put 12 V straight to the socket though. In the MAX A/C test mode the compressor clutch definitely "clacked" closed so that part of the test is okay.

I unscrewed the relay socket bracket and got underneath to confirm the bottomside of the socket was all still snug and no loose connectors. It looks fine and doesn't seem to wiggle much.

I got thinking it was related to the diodes that are inline with that wiring and was surprised to see only one in place (it was black and marked 294 I think it was). The other diode location had the male and female connectors plugged directly together with no diode in the middle.

We have an old complete wiring harness here in a box, so went looking for a replacement diode. I found another black one marked "294", and some others which were blue or red and some marked 297 I think it was. I put the black 294 one inline in the missing spot and still no change in the fans not coming on.

What's the scoop on those diodes again? I'm no electrical wizard, so a refresher might be helpful. Can I test these somehow? I thought to put my multimeter on them to test continuity, or so I think I was, and all of the diodes tested close to the same Ohms (I wanted to say it was in the range of 525-550 Ohms, possibly with a decimal place in the wrong spot there?). Could it be as simple as these diodes are my problem? Do they sell these at the diode store? (hehe) What's the significance of the numbering on them?

I gave up for the moment on the fans and looked peering around at the coolant temperature sensor. I could definitely see it and it is definitely still connected snugly to the wire coming off it. It disappears (green wire) back under the top of the engine heading back to the rear fascia side. I can't see where it goes other than to assume it meets up with the harness. I had previously checked WHITE bulk head connector #29 and it was a good connection.

Any other ideas as we work through this?

[David T]

There was probably nothing wrong with the diodes in the first place but now we have to worry if you installed them wrong. It is VERY important which way they are installed. They work like a one-way check valve, allowing the electric to go in only one direction. Installed backwards they will not work they way they should in the circuit. To test a diode you measure resistance in one direction and then reverse the leads and measure it in the other direction. One direction should have a much higher resistance.
David Teitelbaum

[Jonathan]

There was probably nothing wrong with the diodes in the first place but now we have to worry if you installed them wrong. It is VERY important which way they are installed. They work like a one-way check valve, allowing the electric to go in only one direction. Installed backwards they will not work they way they should in the circuit. To test a diode you measure resistance in one direction and then reverse the leads and measure it in the other direction. One direction should have a much higher resistance.
David Teitelbaum

Thanks David. I'm not too too worried about having installed them backwards, because from what I saw they have a male and female end on them and so do the connectors, so it looks like they can only be installed in one direction.

I have the wiring schematic for the fan circuit, and can see the wiring colours. If I were to look at markings on the diodes or point the male or female end in a certain direction, how should they be installed? I can measure the resistance again... which direction should the higher resistance be? I assume the higher resistance should be in the direction you don't want current to flow? ...which would be pointing to which wire colour?

Do you know what the significance of the numbering is on them? Do they come in different sizes? Are they prone to failing in some way? We can get new ones if need be...

[OverlandMan]

What's the scoop on those diodes again? I'm no electrical wizard, so a refresher might be helpful. Can I test these somehow? I thought to put my multimeter on them to test continuity, or so I think I was, and all of the diodes tested close to the same Ohms (I wanted to say it was in the range of 525-550 Ohms, possibly with a decimal place in the wrong spot there?). Could it be as simple as these diodes are my problem? Do they sell these at the diode store? (hehe) What's the significance of the numbering on them?
?

I'm no expert on the specifics of this project but a DIODE can be thought of as a one-way valve. It only lets current pass in one direction and not the other so as to prevent back-feeding. You can test this by doing a continuity test from both ends. It should work one direction and not the other. Typically they'll have a color pattern or arrow showing the current flow direction.

[Farrar]

I had a bad diode in the cooling fan circuit once and verified it by simply removing it and connecting the two male/female terminals, then jumpering the Otter-stat. If this works on your car, you can buy another diode from your vendor of choice. If you *must* run the car while you wait for the replacement diode, you can steal one of the black ones from the courtesy light circuit.

[Ron]

Thanks David. I'm not too too worried about having installed them backwards, because from what I saw they have a male and female end on them and so do the connectors, so it looks like they can only be installed in one direction.

I have the wiring schematic for the fan circuit, and can see the wiring colours. If I were to look at markings on the diodes or point the male or female end in a certain direction, how should they be installed? I can measure the resistance again... which direction should the higher resistance be? I assume the higher resistance should be in the direction you don't want current to flow? ...which would be pointing to which wire colour?

Do you know what the significance of the numbering is on them? Do they come in different sizes? Are they prone to failing in some way? We can get new ones if need be...

294 = 1 Amp diode
297 = 3 Amp diode
Stock ones both only plug in one way (available at DMCMW, and others).
Arrow points the direction of current flow. They should read ~0Ω one way, and, VERY high if not infinite, "∞" or "OL" the other way.
The stock ones are bad about having cold solider joints (wiggle their terminals while you test).

[Jonathan]

294 = 1 Amp diode
297 = 3 Amp diode
Stock ones both only plug in one way (available at DMCMW, and others).
Arrow points the direction of current flow. They should read ~0Ω one way, and, VERY high if not infinite, "∞" or "OL" the other way.
The stock ones are bad about having cold solider joints (wiggle their terminals while you test).

Cool guys. I will see about testing out this theory... but it might be through a different owner as the car might be changing hands in the near future...