RPM and voltage meter drop

3942 Views 38 Replies 11 Participants Last post by holmz, Jun 1, 2014

Autocross7

Discussion Starter · Apr 12, 2014

So, 88' Esprit - Bosh car - Federal

When I hit the brake, turn on the head lamps, or whatever that would cause an electrical pull, I get a significant drop in rpm and the voltage meter drops... a lot.

So, my thought initially was maybe the ground point is indeed dirty again. Located in the typical "what the hell spot" on the passenger side chasis just far enough forward to be a PITA. A ground cable comes from the battery and slides over a post held in place by a nut...

With the rear wheel removed I was able to get the nut off and, while everything appeared clean, I cleaned it up anyway...

then I was in the mood, and did the same with the grounding straps under the car and the one that runs down more or less on the driver's side in front of the driver... even though these do not tie directly into the running of the engine as far as I know.

Any way, as expected this really did not help. So... I am thinking voltage regulator/alternator are going out.

The car also will randomly just start running like crap. Sputter, no power, etc... and this seems to have been getting worse in lock step with the voltage and rpm drop being noticed.

I guess I'll pull the alternator and have O'Riley's test it (as they have folks where I am that seem to actually know something beside looking up part numbers in a computer).

Any other thoughts?

Thanks,
Cameron

1 - 20 of 39 Posts

maxvelocity

· #2 · Apr 12, 2014

If your headlights go low on idle and brighten up when you rev the engine its good to check the alternator. I'm sure you checked the obvious like a loose alternator belt. I don't know how sensitive the Bosch FI is to voltage drops but the Delco management does not like it one bit. When my alternator went out on my old SE my engine acted really weird and it backfired when the voltage dropped. I called my wife to bring a spare battery so I could drive the car home. It ran fine the 2 miles back to home with the spare battery. When I had the alternator fixed car was fine after that. Maybe the Bosch reacts the same way.

When I have to change out my alternator on this one I think I'm going over 100A because of the added electrical load on my car

Autocross7

Discussion Starter · #3 · Apr 12, 2014

maxvelocity said:
If your headlights go low on idle and brighten up when you rev the engine its good to check the alternator. I'm sure you checked the obvious like a loose alternator belt. I don't know how sensitive the Bosch FI is to voltage drops but the Delco management does not like it one bit. When my alternator went out on my old SE my engine acted really weird and it backfired when the voltage dropped. I called my wife to bring a spare battery so I could drive the car home. It ran fine the 2 miles back to home with the spare battery. When I had the alternator fixed car was fine after that. Maybe the Bosch reacts the same way.

Bosch K-Jet is notorious for being sensitive to voltage... :facepalm

It semms this alternator need to be pulled and re-built (the voltage regulator anyway) about every 5-7 years. And t seems it has been about that long ago. If the mounting was not so specific, I might explore a newer design replacement.

Every hear of anyone dong this and being successful without a major re-engineering project?

jtrealty

· #4 · Apr 12, 2014

Look for sticky black goo dripping out of the bottom of the alternator. If you see that the alternator has to come out. Also make sure the belt is not loose and slipping.
David Teitelbaum

maxvelocity

· #5 · Apr 12, 2014

I think a few have used the Bosch AL49X normally used in BMW I think it is a 90A.
I think Atwell has one but not sure.
I have seen a 110A for an Esprit.
I'm also slowly migrating to LED lights as they fail to lessen the load

glb

· #6 · Apr 12, 2014

Wouldn't one put a voltmeter on the battery to check alternator output?

Look for ~ 14.2 volts. Check at idle and higher revs.

If the voltage is lower at the post (vs the cable), the cable connections are loose and/or dirty.

Have I misunderstood?

maxvelocity

· #7 · Apr 12, 2014

glb said:
Wouldn't one put a voltmeter on the battery to check alternator output?

Look for ~ 14.2 volts. Check at idle and higher revs.

If the voltage is lower at the post (vs the cable), the cable connections are loose and/or dirty.

Have I misunderstood?

Yeah he could do that. But it is a known trouble item to Esprit's that every 5-7 years to expect a failure of that Valeo especially if the black goo of death is present LOL. Doesn't have to be present for failure but if the goo is there no need to check further

Autocross7

Discussion Starter · #8 · Apr 12, 2014

glb said:
Wouldn't one put a voltmeter on the battery to check alternator output?

Look for ~ 14.2 volts. Check at idle and higher revs.

If the voltage is lower at the post (vs the cable), the cable connections are loose and/or dirty.

Have I misunderstood?

Yes, this will check for volts. My multi meter reads about the same as the voltage meter in the car. However, this does not determine amp out put. I could have good voltage and bad amperage... this is what I think is the issue...

Pulling the alternator is not my favorite thing to do, so I tried to rule out other stuff. The plugs, wires, distributor car, and coil are all less than a year old... so once the ground points were cleaned up... I am out of ideas beyond the alternator. Plug read is perfect BTW... tanish grey as it should be.

The alternator front is not goo'd up... but, it does indeed have a nasty black coating that is a bit more grease and powder like than goo... this is not belt material. Belt is good and tension is good...
Cameron

Type82

· #9 · Apr 12, 2014

Cameron,
You should have the battery and alternator load tested. Any auto parts store or garage can do that for you. Just reading battery voltage is not going to tell you much, I was burned doing that once. The amperage the alternator is putting out needs to be checked. The battery under a load test should read no less than 10 volts, if it goes lower the battery needs to be replaced.
Of course if there is black goo on the A/C compressor the voltage regulator has melted down. If I recall JAE sells just the regulators, my Valeo cost me around $400. Some have converted their cars over to a Bosch alternator.

Robert

carbuff

· #10 · Apr 12, 2014

The '88s (and most of the older Esprits) have a convenient voltmeter right there on the dash. One of the most useful bits on the instrument panel!

I have the Bosch AL49X in my car now, purchased at Rock Auto. It is MUCH better at providing current at idle RPMS than the Valeo.

My OE Valeo alternator lasted 78K without failure BTW, but it DID have the onerous drip under the VR when I removed it.

++++++++++

If the indicated voltage drops as much as Cameron says, I'd wager that the present alternator is toast. TADTS

PS, I've never seen an issue with Bosch FI due to low voltage, but then again my alternator worked as intended. After all, K-Jet IS primarily a mechanical system with Electronic Band Aids for low RPM emissions...

glb

· #11 · Apr 12, 2014

OK. But, the voltmeter test is too easy to pass up.

I once diagnosed a bad cable this way. And, the test ensures post-to-cable connection is good.

How are alternators mounted in these cars? Is there any rubber, for instance?

Asking because my Elan went thru 2 alternators until I bought a mount that did not transmit all vibrations to the unit. Then, never needed another.

glb

· #12 · Apr 12, 2014

Atwell,

Going to C&C @ Paul Miller tmw?

BTW, mig welder works fine. Thanks again!

PS: I don't know from where the in car voltmeter picks up.

MRDANGERUS

· #13 · Apr 12, 2014

OE alt = NG POS
Got 200 Amp alt = never prob any mo

sleekgt

· #14 · Apr 13, 2014 (Edited)

MRDANGERUS said:
OE alt = NG POS
Got 200 Amp alt = never prob any mo

NG POS = "No Good Piece Of Silicon"

From Autocross 7:

>The alternator front is not goo'd up...
> but, it does indeed have a nasty black coating that is a bit more grease and powder like than goo...

Here's a picture of the black goo - it will be on the BOTTOM of the alternator, not the FRONT:

Here's my full album showing the failing Valeo voltage regulator goo issue:

http://s413.photobucket.com/user/eb...Esprit Turbo alternator failure?sort=3&page=1

Some useful previous discussions:

http://www.lotustalk.com/forums/f164/what-voltage-idle-88-esprits-142889/#post2071753

http://www.lotustalk.com/forums/f164/what-voltage-idle-88-esprits-142889/#post2072529

A video for an 88 and the 'normal' behavior:

88 Esprit voltagex640 - YouTube

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Autocross7

Discussion Starter · #15 · Apr 13, 2014

Cool. thanks for the post! I'll be pulling it tonight or tomorrow night...

amanda11270

· #16 · Apr 13, 2014

Your alternator is going out if you have a voltage fluctuation like that, I dealt with that headlamps dimming issue for a year before replacing the alternator, I first thought it was "just that way", however after replacing it with a Duralast from Autozone that crossed to some BMW, it reads now like a more modern cars alternator. The only slight fluctuation now is when the idle drops too low, which seems to be a seasonal adjustment of the idle speed/clean throttle bodies.

The one thing I stress is look at the alternator prior to leaving any store with one, as its a slight job to install one in the Esprit, and I bought three before I got one I felt comfortable installing, they were all remanned and I ended up going to 4 autozone's (seriously, no lie) before finding one that I was comfortable installing. The first one, was rusty, right out of the box, I didnt find out until I got it home. I kept returning them and then looking at the one I was buying. I dont remember why I stuck with Autozone, I think they would only exchange it and not give me a refund for some reason. And whatever BMW it fits must be rare too, as Autozone only stocked one per store, hence four stores later I found what I thought was a good one.

I think one of these alternators had a completely different shaft also, probably compatible with the BMW's pulley, but not the Lotus.

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Autocross7

Discussion Starter · #17 · Apr 13, 2014

When I lived in Mobile this was a non issue. There is a shop there that rebuilds most anything and they do a great job.

I have to hunt around in the Tuscaloosa area. Prob have to go to Birmingham?

At any rate, if it looks like the voltage regulator when I get it off... I put out a call to Jeff and JAE... as noted above it is possible they sell just the voltage regulator.

I'll bench test it of course!

Cameron

jtrealty

· #18 · Apr 14, 2014

Autocross7 said:
When I lived in Mobile this was a non issue. There is a shop there that rebuilds most anything and they do a great job.

I have to hunt around in the Tuscaloosa area. Prob have to go to Birmingham?

At any rate, if it looks like the voltage regulator when I get it off... I put out a call to Jeff and JAE... as noted above it is possible they sell just the voltage regulator.

I'll bench test it of course!

Cameron

Although the voltage regulator is what usually fails, the goo gets into the brush holder and causes the brushes to make intermittent contact. It is very difficult to clean the brush holders and the brushes are probably worn anyway so it needs to be replaced. Most shops will also want to clean the commutators and replace the bearings. By time you do all of that it can be cheaper to just get an exchange unit, faster too. Especially if you also need bridge diodes or there is a problem with the rotor or the stator coils.
David Teitelbaum

Autocross7

Discussion Starter · #19 · Apr 20, 2014 (Edited)

Okay, so got the alternator off my car...

No visible black goo...
Removed the voltage regulator... looks totally intact.
Removed the black plastic cover and short of some dust everything looked good.
Rotation is smooth by hand. No grinding - scratchy - whatever...

But! I thought, it's off. I'll take to a shop and get it bench tested. To my (prob should not be) amazement dumb-assery in 'Merika had now fully materialized. apparently without being able to match to a specific vehicle, an alternator test can no longer be done!

"Really?", I asked 3 different shops. There is a single post connection and it needs a ground. But nope. No exact vehicle match in the computer and no test can be done. So, O'Riley's has now de-evolved into button pushing and PC drivers and not car guys.

Awesome!

Anyway, I am cleaning the dust off everything and cleaning up the bay in the general area that is accessible with the alternator out.

I'm going to pull the distributor cap and check it... although it is only a year old and brass from R and D Enterprises.

Beyond the ground points on the body where cables bolt in... is there any other area I should clean regarding making sure grounding is good?

Cameron

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jtrealty

· #20 · Apr 21, 2014

Autocross7 said:
Okay, so got the alternator off my car...

No visible black goo...
Removed the voltage regulator... looks totally intact.
Removed the black plastic cover and short of some dust everything looked good.
Rotation is smooth by hand. No grinding - scratchy - whatever...

But! I thought, it's off. I'll take to a shop and get it bench tested. To my (prob should not be) amazement dumb-assery in 'Merika had now fully materialized. apparently without being able to match to a specific vehicle, an alternator test can no longer be done!

"Really?", I asked 3 different shops. There is a single post connection and it needs a ground. But nope. No exact vehicle match in the computer and no test can be done. So, O'Riley's has now de-evolved into button pushing and PC drivers and not car guys.

Awesome!

Anyway, I am cleaning the dust off everything and cleaning up the bay in the general area that is accessible with the alternator out.

I'm going to pull the distributor cap and check it... although it is only a year old and brass from R and D Enterprises.

Beyond the ground points on the body where cables bolt in... is there any other area I should clean regarding making sure grounding is good?

Cameron

Most of these chain auto stores can't bench anything. Try to find a rebuilder in your local area. It is possible you just need a fresh set of brushes to replace the ones that are now too short and worn out. The absence of black goo does not rule out a blown voltage regulator.
David Teitelbaum

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