problem with warning lights at startup

[filterway]

Hi!

I noticed that some warning lights don't light at startup. I checked all light by removing the cluster and all lights works. The discharge light (battery symbol) and radiator light are the 2 faulty.

Does anyone have an idea what's wrong with these 2 warning lights? What is the component who control theses warnings lights at startup? (they supposed to be on for 4 to 8 second i think)

For the radiator light, i tested the warning switch, the bulb, everything is fine expect the light don't light at startup...

same thing with the discharge warning light (battery). The repair manual say the IC from the alternator could be the problem, but i checked the charging system and everything look good.

Any idea?

Jerome

[nikifix]

Jerome ,more than likely the rectifier bridge diodes are dead..........is your power steering pump leaking? Nik

[filterway]

Jerome ,more than likely the rectifier bridge diodes are dead..........is your power steering pump leaking? Nik

Is it diodes inside the alternator?

power steeeing is not leaking but i can see traces of power steeting fluid where it is supposed to leak. No drops, just kind humid around the top of the pump.

jerome

[nikifix]

yes the diodes are in the alternator and convert AC to direct current I had this problem a month ago because of a leaky steering pump....though I am sure diodes can die just for the hec of it. I had about 10 volts charging and no dash lights
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[timsrv]

Except Jerome doesn't have a charging problem............only a warning light problem. Right Jerome?

[originalkwyjibo]

I just went through this with my '88. According to this thread, http://www.toyotavantech.com/forum/s...warning+lights no dash lights is likely a bad regulator so I went this route. On vehicle test showed bad regulator as expected. Bench test to obtain warranty replacement said the alternator was working great. No P/S leaks, that was fixed properly a few years ago and this alternator was new since then. After the bench test I started testing wiring and it all checked out good. After scratching my head awhile I tested everything again and then with the alternator unplugged I grounded the warning light wire with a jumper while the cluster was plugged in. Still no lights. I checked for continuity along the circuit and all was good up to the cluster until I got to the warning light socket itself. Bingo! No continuity between the cluster connector and the warning light socket. Both the alt and rad warning lights are wired in series and run through a diode on the back of the printed circuit which was bad. I had a local electronics shop run by a retired Vietnam era Navy vet fix it for me for a very reasonable price and now everything works. I had the alternator tested on the vehicle again to verify and it tested fine. I wasn't aware a bad warning light circuit could cause an alternator to test bad. I was going to post about this with pics on the above mentioned thread but just haven't had time yet.

[filterway]

Except Jerome doesn't have a charging problem............only a warning light problem. Right Jerome?

Exactly Tim, but the problem looks like originalkwyjibo said in his post. The diode on the back of the printed circuit may be the problem.

What is the specs of this diode? i presume it's a simple job of welding.

Jerome

[filterway]

...Bingo! No continuity between the cluster connector and the warning light socket. Both the alt and rad warning lights are wired in series and run through a diode on the back of the printed circuit which was bad. I had a local electronics shop run by a retired Vietnam era Navy vet fix it for me for a very reasonable price and now everything works. I had the alternator tested on the vehicle again to verify and it tested fine. I wasn't aware a bad warning light circuit could cause an alternator to test bad. I was going to post about this with pics on the above mentioned thread but just haven't had time yet.

I Tested radiator warning light and it lights by bypassing the switch. My question is, if the diode is wrong, how the radiator warning light can lights? do these lights (discharge and radiator) can light through another circuit?

Jerome

[timsrv]

It's wired that way so the driver and/or tech can view status of the warning system each time the vehicle is started. Like Original said, it's most likely a problem with your cluster, and a bad diode is a reasonable fault to expect. Tim

[originalkwyjibo]

I would have to look at my manual and the pics I took of the circuit board when I get home after work. I know there were four diodes total on the circuit and believe the rad and alt light each had their own wire in different directions as these do have a specific orientation for polarity. My understanding of the circuit is the positive side is hot when the key is turned on and the negative side grounds through the alt. Once the van is started there is current on both sides and the lights turn off since the ground has been removed. I assume the diodes are there to keep the lights from feeding back through each other since they each have their own power source on the positive side.

[originalkwyjibo]

I was just looking at a schematic online and it looks like the diode is on different sides of the alt light in the printed circuit for DX and LE. Mine is an LE. If your's isn't, I presume this may make them behave differently.

[filterway]

I was just looking at a schematic online and it looks like the diode is on different sides of the alt light in the printed circuit for DX and LE. Mine is an LE. If your's isn't, I presume this may make them behave differently.

Mine also is LE. There is a pic of electric diagram. i'm not an expert but i think is what you talk about.
the diode is on one side for the DX and on the other side for the LE. i'm curious what's the difference on each model. Have you information about the kind of diode is there?
Jerome

[filterway]

well, after studying the electric diagram, i realize that every warning light with diode doesn't light, this include discharge warning light (battery), radiator warning light, oil level light (low level) and brake warning light.

i use this video to compare wath should light https://www.youtube.com/watch?v=IR_GfrDOFM0

it's not a major problem but i'm a perfectionist and like when everything work fine

Jerome

[filterway]

i tested all 4 diodes. each show a read around 543 (don't know what kind of unit is) on one way and no continuity on the other way (multimeter read a value of 1)

For now i don't know where to check the problem. Bulbs are ok, diodes are ok. i did not test alternator yet but the readings show a charge of 14.0-14.3 V.

any idea?

Jerome

[timsrv]

It's possible to have a working alternator but still have an open circuit in the "L" terminal wire (yellow). Could even be a problem with the regulator. The "L" side of the regulator is unrelated to the charge side, so it's possible to have this issue and still have the charge side function. I'm not saying this is your problem, I'm just saying it's a possibility. Tim

[filterway]

It's possible to have a working alternator but still have an open circuit in the "L" terminal wire (yellow). Could even be a problem with the regulator. The "L" side of the regulator is unrelated to the charge side, so it's possible to have this issue and still have the charge side function. I'm not saying this is your problem, I'm just saying it's a possibility. Tim

I'll check on this side when i'll change the alternator this spring.

thanks Tim

[originalkwyjibo]

Have you tried unplugging the alternator connector near the overflow bottle and grounding the "L" terminal(yellow wire)on the chassis side harness? If you do this with the key on it should light all the warning lights that would normally be on. Basically the circuit grounds through the alternator until the engine is started. Doing this would mimic that function. If this doesn't result in a lit charge light something is still wrong between the alternator and the warning light. If it does light everything up then it may be a bad regulator as suggested by Llamavan in the post previously linked to.

[originalkwyjibo]

Here's the diode info in case anyone else needs it. I circled the location of the diode I had replaced in both images. It was the top diode of the two circled. The one oriented diagonally. The diode used as recalled by the guy that did the work was a 1n4002 with a 100v piv @ 1 amp. He used a different soldering technique where he applied heat through a woven fabric to de-solder and keep from burning through the membrane. This made the solder draw up into the fabric. Not sure what it was made of though. I think he referred to it as conductive soldering.

[filterway]

Have you tried unplugging the alternator connector near the overflow bottle and grounding the "L" terminal(yellow wire)on the chassis side harness?

Do you have a picture to show exactly where it is located?

[originalkwyjibo]

It's the round one indicated by the left arrow.